As many as 30 million people travel to the mountains in the western United States each year1 to enjoy the beauty and outdoor activities the terrain has to offer. Travelers may worry about altitude sickness upon arrival. However, another important side effect of high altitude exists: muscle atrophy. While it may not be noticeable during visitors’ short time at high altitude, it is still a remarkable effect the elevation has on human bodies.
Muscle atrophy is a scientific term for the loss of muscle mass2; essentially, the muscle fibers shrink due to loss of important contractile proteins and organelles, which are essential parts of muscle fibers3. This means that the muscle won’t be able to perform as well4, especially in terms of endurance and power; tasks that are normally easy, such as walking up a flight of stairs, may be significantly more tiresome or difficult.
An elevation is considered high altitude when the location is 2400 meters or more above sea level4. This is about 7,874 feet of elevation. Over 140 million people worldwide live at or above this altitude4, making the issue of altitude-induced muscle atrophy very relevant to many.
Hypobaric hypoxia, which occurs at high altitudes, is a decreased barometric pressure in addition to a decrease in oxygen availability1. This is a double whammy for visitors for two reasons: a lower pressure won’t be able to push as much oxygen into tissues, and less availability of oxygen will diminish the amount that tissues receive1. These two conditions result in less oxygen getting to body systems1 that usually obtain a good amount. This is especially pertinent to muscles because of their prevalence in the human body.
Muscle atrophy is indicative of a disproportion between the process that builds protein and the process that breaks down protein in muscles2. Several studies have shown that when muscles receive less oxygen, such as in hypobaric hypoxic states, muscle protein degradation is boosted while muscle protein creation dwindles2,3,4,5. This results in an overall deficit of protein in the muscle, which is meaningful because muscles store the most protein compared to any other organ in the body3.
Currently there are no official guidelines for prevention of muscle atrophy due to hypobaric hypoxia. There are also no medications that currently counteract the loss of muscle3, although researchers are now turning their focus to ways of maintaining the balance of protein breakdown and building in muscle.
Despite the fact that these measures are suggested for preventing high altitude illness, it may be beneficial in general to stay hydrated, ascend slowly to altitude, eat a balanced diet, and remain active1. Foods and herbal supplements rich in antioxidants may be helpful in preventing muscle wasting during exposure to hypobaric hypoxia4, although there is no direct evidence to support this theory yet. Overall, it would be beneficial to maintain good nutrition throughout the visit to the mountains. Moderate exercise may help visitors acclimatize, although overly spirited exercise can cause other altitude-related problems1.
How are people who live at altitude affected by muscle atrophy? At the moment, studies are geared more towards the effects that altitude has on people who visit from lower elevations. Once the body has acclimated to the altitude, oxygen utilization and distribution will improve greatly and will ensure that tissues receive more oxygen1. This may explain why people who live at high altitude for long periods of time are able to maintain and oftentimes increase their muscle mass. Even so, people who live at high altitude should still eat a healthy diet and drink a good amount of water to make sure their bodies can function optimally.
It is important to be aware of the side effects that altitude has on the bodies of sea-level visitors. There is still more research to be done regarding effective treatment options for this particular type of muscle atrophy. Knowing that high altitude causes muscle atrophy can help people be aware of their activity level and diet and may modify how people choose to ascend to the mountains. This consequence of high altitude should not prevent people from enjoying all that mountainous regions have to offer.
Grace Barrett is a Physician Assistant student at the University of St. Francis in Albuquerque, New Mexico. Born and raised in Grand Rapids, Michigan, Grace attended Michigan State University where she received degrees in both Physiology and Spanish. After completing her rotation in pediatrics with Dr. Chris, Grace will have rotations in New Mexico, Michigan, and California before graduating in April 2020. She is hoping to explore urology as her elective rotation. Grace enjoys baking cookies, being active, watching Chopped on the Food Network, spending time with family, and planning her wedding (in August 2020).
1. Gallagher SA, Hackett P, Rosen JM. High altitude illness: Physiology, risk factors, and general prevention. UpToDate. https://www.uptodate.com/contents/high-altitude-illness-physiology-risk-factors-and-general-prevention. Published September 20, 2017. Accessed July 18, 2019.
Our brain is a highly demanding organ that requires a constant supply of oxygen, evidenced by how quickly a drowning victim loses consciousness. But apart from being under water, many other places on Earth expose our brains to the low oxygen levels that cause hypoxia, or lack of oxygenated blood flow to the brain. The most common of these places is that of high altitude (current studies in the US often define this as above 8,000 ft.). But how does long-term exposure to the low oxygen levels in these environments affect our brains? Recent studies have revealed new dangers from exposure to extremely high altitudes (15,000+ ft.), and they suggest that our brains also feel the impact at less extreme elevations as well. As concerning as these findings may be, further studies are being done to increase our knowledge of these effects and luckily, methods to prevent and avoid them do exist. But in order to avoid them effectively, we must first understand the dangers that high altitude presents.
Extremely high altitude locations are some of the most impressive and breath-taking places in the world. They often serve as bucket list checkpoints for travelers and mountaineers everywhere. However, in a 2006 study by Fayed et al, a new risk for extremely high altitude hikers (15,000 ft+) was revealed1. MRI scans were performed on the brains of those returning from locations including Mt. Everest, Mt. Aconcagua, Mont Blanc and Mt. Kilimanjaro1. Shockingly, almost every Mt. Everest climber returned with brain changes on their MRI scans. They revealed cortical atrophy and enlargement of their Virchow-Robin spaces, processes that are usually associated with aging1. The amateur of the group seemed to suffer the most permanent changes with subcortical lesions as well1. Where there had been one unaffected hiker in the Everest group, none returned from the Aconcagua expedition without brain changes. Four hikers also showed subcortical lesions1. Unfortunately, and even more concerning, most of these changes were still present on MRI scans several years afterward as well1.
A follow up study in 2015 by Kottke et al. examined mountaineers before and after a 7,126m (23,373ft) ascent and found that none had subcortical lesions afterward2. However, there were increases in cerebral spinal fluid fractions and decreases in white matter fractions in several of the hikers. They also took it a step further and related it to the hypoxic levels and mountain sickness symptoms that the individuals suffered and were able to correlate these episodes with more significant brain changes2.
More research must be done to determine what these brain changes mean and how they will impact the lives of these individuals later in life. However, researchers have also found ways to approach altitude that seemed to lessen these effects. The number one suggestion that professionals share to prevent the possibility of permanent brain changes is simple; ascend slowly1. The studies that found permanent brain changes in extreme altitude hikers seemed to find worsened effects in the amateurs that ascended too quickly versus the professionals that had ascended correctly, over time1. Oxygen supplementation and other methods to prevent acute mountain sickness during the climbs seemed to help as well1.
For those of us that refrain from scaling some of the world’s tallest mountains, but frequently visit or reside in moderately high altitudes, our brains can also be affected. Abrupt elevations in altitude from a low level environment have been shown to affect people’s memory storage and recall3. It has also caused impairments in concentration, aphasia and finger tapping speed temporarily3. In a 2016 study that examined young, healthy individuals living at altitudes of 3650 m (11,975 ft) for a minimum of three years, significant impairments in attention were revealed4. Early and late stages of attentional processes were impacted in this study group when compared with a control group4. These impairments were also made more significant when larger amounts of perceptual input, or distractions, were added4.
In terms of the long-term high altitude group, attention span data did show impairment in early and late stages, but interestingly, changes in brain activation on brain scans were proposed as possible mechanisms to attempt to compensate for this4. Moreover, it was also found that later stages of attentional processes showed less brain activation in the high altitude group, but they found that this discrepancy lessened the longer that the individual lived at altitude, suggesting adaptation was occuring4.
Rather than residing at moderately high altitudes, traveling to them can also affect the brain. The same advice of ascending slowly at extremely high altitudes is also applicable here. Giving the body time for appropriate acclimatization is key to preventing any physical symptoms as well as any confusion, sluggish thinking, or difficulty concentrating and focusing1. Proper hydration, nutrition and the occasional oxygen supplementation can lessen symptoms as well.
In conclusion, more research is needed to study the effects of permanent brain changes from extremely high altitudes as well as to determine if there really is a danger toward our attention spans, or any other cognitive processes, from living at high altitude. Although it is important to be aware of these risks, very few residents and adventurers let it hold them back from visiting and living in some of the most incredible places in the world. As long as we approach with an understanding of the dangers, prepare appropriately and always ascend slowly, not even our brains can hold us back from the adventures to be had in these amazing locations.
Jenna Bradfield is a Physician Assistant Student at the University of St. Francis in Albuquerque, New Mexico. Prior to PA school, she completed her undergraduate studies at Southern Utah University where she played collegiate volleyball as well. She is currently completing her third clinical rotation in Pediatrics at the Ebert Family Clinic. As she is originally from a small town in Utah, she has and will be completing several more rotations in her home state along with other rotations in New Mexico and Texas. She grew up loving the outdoors and sports, and also enjoys physical fitness, music, reading and spending time with friends and family.
1: Fayed, N., Modrego, P. and Morales, H Evidence of brain damage after high-altitude climbing by means of magnetic resonance imaging. American Journal of Medicine. 2006. 119, 168.e1-168.e6.
2: Kottke, R. Hefti, JP. Rummel, C. Hauf, M. Hefti, U. Merz, TM. Morphological brain changes after climbing to extreme altitudes – a prospective cohort study. PLoS One. 2015; 10(10): e0141097
3: Hombein, TF. Long term effects of high altitude on brain function. Int J Sports Med. 1992;(13) Supple 1:S43-5.
4: Wang, Y. Ma, H. Fu, S. Guo, S. Yang, X. Luo, P. Han, B Long-term exposure to high altitude affects voluntary spatial attention at early and late processing stages. Scientific Reports. 2014; (4) 4443.
Can high altitude climate therapy (HACT) result in long term benefits for adults with severe asthma?
How much do you know about asthma? Have you ever considered that the air we breath every day is often filled with environmental triggers that worsen asthma symptoms making it more difficult for asthmatics to breath? Did you realize that at elevation many of those environmental triggers such as air pollution and pollen are gone? The rumors are true, mountain air really is better and residents at altitude are truly lucky to be breathing in fresh, clean, crisp mountain air on a daily basis.
Based on data collected by The Global Initiative for Asthma (GINA), as of 2004 it was estimated that 300 million people of all ages worldwide suffer from asthma. That number is projected to increase to 400 million by 2025! In 2010, the CDC documented that 1.8 million people in the US alone visited the emergency department for asthma related care and of that number at least one third of them had to be hospitalized for severe symptoms.
Asthma is characterized by: 1) Chronic airway inflammation, 2) intermittent and reversible airway obstruction, and 3) bronchial hyper-responsiveness (the tendency of airways to narrow in response to a variety of triggers in the air that have little effect on people without any respiratory disease). Patients with asthma often complain of intermittent cough, shortness of breath (or difficulty breathing), and wheezing. This classic presentation is often worsened by triggers such as allergens, pollutants, tobacco, cockroaches, pollen, mold, stress, upper respiratory infections, weather and/or exercise. Symptoms are alleviated with bronchodilator medications, which act to open the airways making breathing easier.
Asthma is conventionally treated in a step-wise fashion, meaning that treatment escalates with increasing severity of symptoms. Patients who suffer from severe asthma on a daily and nightly basis are often on multiple medications in an attempt to control their symptoms. These usually include an inhaled corticosteroid medication, a long-acting beta-2 agonist. Some start oral steroids and some even require biologic or immune modulating agents. Patients that fall into this category often suffer from a decreased quality of life, multiple doctor or emergency room visits and have difficulty controlling their symptoms on a regular basis.
Recently, researchers have been investigating different avenues to provide relief for patients suffering from severe asthma symptoms. Studies published on high altitude climate therapy (HACT) are showing positive outcomes for adults with severe asthma that are refractory to conventional treatment.
An article published in 2018 in The European Journal of Allergy and Clinical Immunology conducted a study to determine if HACT resulted in long term benefits for asthmatics even after returning to sea level. Patients included in this study had to fall into the category of an adult with severe uncontrolled asthma symptoms despite conventional treatment methods. These patients were enrolled in a 12 week multi-disciplinary treatment program with environmental trigger avoidance in an alpine climate at an altitude greater than 1500 m (4921.26 ft). After the conclusion of the program, patients were followed for one year with repeat evaluations every 3 months to assess the long term effects of this therapy on their asthma symptoms.
This is the first study to show a decrease in exacerbations and improvement in asthma control up to 12 months!! This was measured in the number of asthma exacerbations, hospitalizations, and oral corticosteroid use before and after HACT treatment. The study showed a decrease in all three categories, which correlates to a positive outcome following this treatment.
While “trigger avoidance” has always been an important aspect of the conventional asthma treatment regimen, it is amazing to see how patients benefit when this is carried out effectively. It is hypothesized that allergens work to continually stimulate and maintain the airway inflammation in asthmatics. When these triggers are removed for a sufficient amount of time, the bronchioles have a chance to recover and decrease the process of ongoing inflammation.
Another proposed mechanism by which this treatment is effective is the decrease in air viscosity at altitude, which benefits the patient by decreasing the thickness of airway mucosa and may even reverse airway modeling. This makes breathing easier for patients and acts to decrease asthma symptoms.
So who can benefit from this treatment? Are all asthmatics created equally?
Scientists and clinicians alike have identified three different groups of asthma patients: 1) severe atopic asthma, 2) persistent eosinophilic asthma, and 3) asthma associated with morbid obesity. While classically these different patient populations respond differently to asthma treatments, it has been found in another study, “Predictors of benefit from high altitude climate therapy,” that HACT improves the quality of life and respiratory function in all patients suffering from severe asthma symptoms. This study sought to investigate if different factors such as age, blood eosinophils (a type of white blood cell), and degree of asthma control prior to admission could predict how much a patient would benefit from high-altitude climate therapy. While this study is making steps in the right direction, it was determined that further patient characterization is required to clearly identify which patients will benefit the most from HACT.
Finally, in a systematic review and meta-analysis on HACT, it was determined that patients experience a statistically significant improvement in lung function following this treatment modality. This review wanted to analyze the quality of research studies completed so far on this topic and also proposed some limitations of the publications so far.
Some things to consider that are still being evaluated include: What is the optimal altitude and duration of treatment in order to see the most benefit? Which patients will experience the most improvement from this treatment? How does this treatment method compare financially with others considering that it is a resource-intensive intervention?
Overall, research on HACT is making exciting headway! So far we have learned that adults with severe asthma can benefit from alpine treatment in some way regardless of phenotype. In addition, many patients experienced lasting improvement for up to 12 months. Be on the lookout as more research is published on this topic. As always, if you are patient suffering from asthma, check in with your primary care provider prior to making a trip to altitude to ensure your asthma is well controlled before arrival. While HACT has been shown to decrease asthma symptoms long term, arriving at altitude unprepared with uncontrolled symptoms could put an asthmatic at higher risk for high altitude sickness. As discussed at the beginning of the article, cold air can be a trigger for asthmatics as well and with that in mind it would be best to visit the mountains during the summer months! Lastly, always be prepared and carry your rescue inhaler with you, especially when traveling to altitude.
Sarah Gordon is currently a Physician Assistant Student at Midwestern University located in Glendale, Arizona. She plans to complete a one year fellowship at Mayo Clinic in otolaryngology/ head and neck surgery after graduation. Throughout her clinical year she has had the opportunity to travel to Denver and Frisco, Colorado, along with completing rotations located throughout the greater Phoenix area in Arizona. When she is not studying, she enjoys cooking new recipes, spending time with friends and staying active through fitness and outdoor adventures.
“Asthma | CDC.” Centers for Disease Control and Prevention, Centers for Disease Control and Prevention, www.cdc.gov/asthma/default.htm.
Fanta, Christopher H. “An Overview of Asthma Management.” UpToDate, Helen Hollingsworth, MD, www-uptodate-com.mwu.idm.oclc.org/contents/an-overview-of-asthma-management?search=asthma adult&source=search_result&selectedTitle=1~150&usage_type=default&display_rank=1.
Fanta, Christopher H. “Diagnosis of Asthma in Adolescents and Adults.” Www, Helen Hollingsworth, MD, www-uptodate-com.mwu.idm.oclc.org/contents/diagnosis-of-asthma-in-adolescents-and-adults?search=asthma definition§ionRank=1&usage_type=default&anchor=H2&source=machineLearning&selectedTitle=1~150&display_rank=1#H3.
Fieten, Karin B., et al. “Less Exacerbations and Sustained Asthma Control 12 Months after High Altitude Climate Treatment for Severe Asthma.” Allergy, vol. 74, no. 3, 14 Nov. 2018, doi:10.1111/all.13664.
Hashimoto, S., et al. “Predictors of Benefit from High-Altitude Climate Therapy in Adults with Severe Asthma.” The Netherlands Journal of Medicine, vol. 76, no. 5, July 2018, pp. 218–225.
Rijssenbeek-Nouwens, L. H., and E. H. Bel. “High-Altitude Treatment: a Therapeutic Option for Patients with Severe, Refractory Asthma?” Clinical & Experimental Allergy, vol. 41, no. 6, 2011, pp. 775–782., doi:10.1111/j.1365-2222.2011.03733.x.
Seys, Sven F, et al. “Effects of High Altitude and Cold Air Exposure on Airway Inflammation in Patients with Asthma.” Thorax, vol. 68, no. 10, 2013, pp. 906–913., doi:10.1136/thoraxjnl-2013-203280.
Vinnikov, Denis, et al. “High-Altitude Alpine Therapy and Lung Function in Asthma: Systematic Review and Meta-Analysis.” 6.2 Occupational and Environmental Health, 2016, doi:10.1183/13993003.congress-2016.pa4293.
A 2009 study from Switzerland found a 12% decrease in risk of death from stroke at 6430 ft. compared to 850 ft. This result was more pronounced in men than women. Since men are more physically active than women in Switzerland, it was thought the exercise at the more hypoxic conditions of higher altitude may benefit them more than for women. The study also noted that being born at a higher altitude had a protective effect on death from cardiovascular disease1.
Strokes occur when blood flow to parts of the brain is cut off causing neurons and other brain cells to die within minutes. Strokes can either be ischemic or hemorrhagic. 80-87% of strokes are ischemic, which means that blood flow to the brain is cut off from a blood clot or other blockage of a blood vessel going to or in the brain. Hemorrhagic strokes are caused by bleeding within the brain (intracerebral space) or in the space surrounding the brain filled with cerebrospinal fluid (subarachnoid space). Risk of stroke is higher in individuals with previous transient ischemic attack (TIA), high blood pressure, previous heart attack, atrial fibrillation, enlarged left atria of the heart, smoking, heavy alcohol use, diabetes, obesity, high cholesterol, and stenosis of the carotid artery2.
Interestingly, on initial exposure to hypoxia at high altitude, blood flow to the brain increases which is split equally between gray and white matter. After 4 to 5 days, blood flow to the brain decreases but is still 13% greater than at sea level. The increased blood flow is needed to maintain adequate delivery of oxygen when the oxygen content of the blood is lower during hypoxia, until other acclimation mechanisms take effect3.
As noted in previous blog posts in response to hypoxia, erythropoietin (EPO) is also released, which increases the production of red blood cells to increase the oxygen-carrying capacity of our blood. Other studies have found that EPO also has a protective effect on neurons. Cerebrovascular endothelial cells have been found to have receptors for EPO and are thus able respond to EPO. Other studies have found that EPO is also involved in brain development of a fetus in utero. Animal studies suggest EPO not only protects neurons from cell death but may enable their regeneration as well. If this translates into humans, it is an important effect for those at risk for stroke4.
In a small clinical trial, patients with middle cerebral artery stroke received IV EPO daily for 3 days after their stroke. These patients had better neurological outcomes with increased physical functioning and independence as measured by Barthel index test results. Following the EPO doses, the size of the cerebral infarct, the damaged area of the brain from blood being cut off during the stroke, was reduced as well4.
Based on this research, Ismailov hypothesized that in the United States, geographic variation in levels of EPO from altitude differences may account for the differences in risk of death from stroke. He termed it the “stroke belt” in the Southeast, with higher rates of death from stroke compared to the Mountain states.
The states in the “stroke belt” are Louisiana (LA), Mississippi (MI), South Carolina (SC), Alabama (AL), Georgia (GA), Arkansas (AK), Indiana (IN), North Carolina (NC), Kentucky (KY), Tennessee (TN), and Virginia (VA), and all are at lower altitude. The mountain states have higher altitude and are North Dakota (ND), Kansas (KS), Nebraska (NE), Arizona (AZ), New Mexico (NM), Wyoming (WY), and Colorado (CO).
Louisiana and Mississippi’s average altitudes are 100 and 300 ft. compared to Colorado and Wyoming with average altitudes of 6800 and 6700 ft4. Since there is increased EPO released in individuals living at higher altitudes, perhaps there is more of a neuroprotective effect at higher altitudes, contributing to the observed lower risk of death from stroke seen in the Swiss study.
Symptoms of Stroke5
Other signs are sudden
Numbness of face, arm, or leg and particularly numbness on one side of body
Difficulty seeing out of one or both eyes
Feeling of dizziness, loss of balance, or coordination
Stephanie Schick is a Physician Assistant student at Rocky Vista University in Parker, CO. She is born and raised in Fort Collins, CO. She started off her clinical year working in pediatrics with Dr. Chris at Ebert Family Clinic. The remainder of her clinical year will be spent closer to home in northern Colorado. In her free time she enjoys spending time with her husband, friends, and family in the beautiful Colorado sunshine.
We’ve learned a lot in the high country this season! For example, it isn’t too late or too warm for a snowstorm. We’ve conducted several interviews with professional, high-altitude athletes, athletic and tourism organizations in Summit County, physicians, podcasters, interns, and a local brewer. They’ve shed so much light on fitness, health, child growth & development, and acclimation at elevation, it warrants a re-cap:
8,000 ft. seems to be the pivotal elevation at which the body starts to experience a significant deficit in the oxygen and water it needs to function, affecting everything from sleep to metabolism.
A plant-based lifestyle has benefitted athletes under extreme training and competitive conditions at altitude.
Training at altitude significantly reduces your ability to reach cardiovascular and strength goals, even while preparing your respiratory and circulatory systems for the severe decrease in oxygen. “Live High, Train Low” is an effective strategy more and more athletes are advocating for.
Preparation for backcountry excursions is as much mental as physical.
Foods high in nitrates (like red beets, red bell peppers and arugula) can facilitate acclimation and recovery.
Oily foods may inhibit your body’s ability to cope with a significant increase in altitude.
We metabolize and experience the effects of alcohol differently at altitude.
Current research suggests some people suffering from Parkinsons disease may experience some relieve from symptoms at higher elevation.
Increased muscle mass requires increased oxygen. Being an athlete does not necessarily mean you will have an easier time acclimating.
As always, the best way to facilitate acclimation and deal with symptoms of altitude sickness is to drink plenty of water, allow yourself ample rest, and monitor your blood oxygen saturation levels with a pulse oximeter.
Be sure to subscribe to keep up with what this summer has in store for your elevated experiences at altitude! And if you have any questions or are eager to read more about a particular topic, let us know in a comment!
Just spoke to one of the brewers at Highside Brewery in Frisco, Colorado. He told me they have to oxygenate the yeast with about sixteen times as much as they do below 8000 ft. elevation in order for the yeast to reproduce enough during the brewing process!
Roberto Santos is from the remote island of Saipan, in the Commonwealth of the Northern Mariana Islands. He has since lived in Japan and the Hawaiian Islands, and has made Colorado his current home, where he is a web developer, musician, avid outdoorsman and prolific reader. When he is not developing applications and graphics, you can find him performing with the Denver Philharmonic Orchestra, snowboarding Vail or Keystone, soaking in hot springs, or reading non-fiction at a brewery.
Living in Summit County, Colorado has its perks – residents are within a 20 to 40 minute drive to five world class ski resorts, and some of the most beautiful Rocky Mountain trail systems are accessible right out our back door. With the endless opportunities drawing residents outdoors to partake in physical activity, it comes as no surprise that Summit County is considered one of the healthiest communities in the country. However, there may be more than meets the eye when it comes to explaining this, as it also has something to do with the thin air.
As a Summit County native, you have likely heard the term “hypoxia” or “hypoxemia” mentioned a time or two. So what does this mean? Simply put, these words describe the physiological condition that occurs when there is a deficiency in the amount of oxygen in the blood, resulting in decreased oxygen supply to the body’s tissues. When this occurs in the acute setting, it may result in symptoms such as headache, fatigue, nausea, and vomiting. These are common symptoms experienced by those with altitude illness, also known as acute mountain sickness. While these symptoms can cause extreme discomfort and may put a huge damper on a mountain vacation, they are not usually life threatening. However, in a small number of people, development of more serious conditions such as a high altitude pulmonary edema (HAPE) and high altitude cerebral edema (HACE) can occur. The treatment for all conditions related to altitude illness is oxygen, whether via return to lower elevations or by a portable oxygen concentrator that allows you to stay where you are. While altitude illness generally affects those who rapidly travel from sea level to our elevation, it has also been known to affect residents returning home to altitude, usually after a period of two or more weeks away. In a very small subset it can occur after a period of only a day or two. This generally occurs in those with a preexisting illness, where altitude exacerbates the condition.
While the acute effects of altitude can clearly have detrimental effects on one’s physical well-being, there is emerging research demonstrating that chronic hypoxia may actually come with several health benefits. Long time Summit County business owner and community pediatrician, Dr. Chris Ebert-Santos of Ebert Family Clinic in Frisco, has spent quite some time studying the effects of chronic high-altitude exposure, and recently attended and presented at the Chronic Hypoxia Symposium in La Paz, Bolivia, the highest capital city in the world.
It is important to first understand the adaptations that occur in our bodies as a result of long-term hypoxia. The ability to maintain oxygen balance is essential to our survival.
So how do those of us living in a place where each breath we take contains about ⅓ fewer oxygen molecules survive?
Simply put, we beef up our ability to transport oxygen throughout our body. To do this, our bodies, specifically the kidneys, lungs and brain increase their production of a hormone called erythropoietin, commonly known as EPO. This hormone signals the body to increase its production of red blood cells in the bone marrow. Red blood cells contain oxygen binding hemoglobin proteins that deliver oxygen to the body’s tissues. Thus, more red blood cells equal more oxygen-carrying capacity. In addition to increasing the ability to carry oxygen, our bodies also adapt on a cellular level by increasing the efficiency of energy-producing biochemical pathways, and by decreasing the use of oxygen consuming processes2. Furthermore, the response to chronic hypoxia stimulates the production of growth factors in the body that work to improve vascularization2, thus, increased ability for oxygenated blood to reach its destination.
So, how can these things offer health benefit?
To start, it appears that adaptation to continuous hypoxia has cardio-protective effects, conferring defense against lethal myocardial injury caused by acute ischemia (lack of blood flow) and the subsequent injury caused by return of blood to the affected area3. The exact mechanism of how this occurs is not well understood, but it seems that heart tissue adapts to be better able to tolerate episodes of ischemia, making it more resistant to damage that could otherwise be done by decreased blood flow that occurs during what is commonly known as a heart attack. This same principle applied to ischemic brain damage when tested in rat subjects. Compared to their normoxic counterparts, rats pre-conditioned with hypoxia sustained less ischemic brain changes when subjected to carotid artery occlusion, suggesting neuroprotective effects of chronic hypoxia exposure4.
Additionally, it appears that altitude-adapted individuals may be better equipped to combat a pathological process known as endothelial dysfunction5. This process is a driving force in the development of atherosclerotic, coronary, and cerebrovascular artery disease. Altitude induces relative vasodilation of the body’s blood vessels compared to lowlanders2. A relaxing molecule known as nitric oxide, or NO, assists with causing this dilation, and in turn the resultant dilated blood vessels produce more of this compound5. The molecule has protective effects on the inner linings of blood vessels and helps to decrease the production of pro-inflammatory cytokines that damage the endothelium5. This damage is what kickstarts the cascade that leads to atherosclerosis in our arteries. Thus, a constant state of hypoxia-induced vasodilation may in fact decrease one’s risk of developing occlusive vascular disease.
The topics mentioned above highlight a few of the proposed mechanisms by which chronic hypoxia may be beneficial to our health. However, do keep in mind that there are potential detrimental effects, including an increased incidence of pulmonary hypertension as well as exacerbation of preexisting conditions such as COPD, structural heart defects and sleep apnea, to name a few6. Research regarding the effects of chronic hypoxia on the human body is ongoing, and given its significance to those of us living at elevations of 9,000 feet and above, it is important to be aware of the impact our physical environment has on our health. Dr. Ebert-Santos is avidly involved in organizations dedicated to better understanding the health impacts of chronic hypoxia, and has several current research projects of her own that may help us to further understand the underlying science.
Kayla Gray is a medical student at Rocky Vista University in Parker, CO. She grew up in Breckenridge, CO, and spent her third year pediatric clinical rotation with Dr. Chris at Ebert Family Clinic. She plans to specialize in emergency medicine, and hopes to one day end up practicing again in a mountain community. She is an avid skier, backpacker, and traveler, and plans to incorporate global medicine into her future practice.
Theodore, A. (2018). Oxygenation and mechanisms for hypoxemia. In G. Finlay (Ed.), UpToDate. Retrieved May 2, 2019, from https://www-uptodate-com.proxy.rvu.edu/ contents/oxygenation-and-mechanisms-of-hypoxemia?search=hypoxia&source=search_ result&selectedTitle=1~150&usage_type= default&display_rank=1#H467959
Michiels C. (2004). Physiological and pathological responses to hypoxia. The American journal of pathology, 164(6), 1875–1882. doi:10.1016/S0002-9440(10)63747-9. Retrieved May 2, 2019. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC1615763/
Kolar, F. (2019). Molecular mechanism underlying the cardioprotective effects conferred by adaptation to chronic continuous and intermittent hypoxia. 7th Chronic Hypoxia Symposium Abstracts. pg 4. Retrieved May 2, 2019. http://zuniv.net/symposium7/Abstracts7CHS.pdf
Das, K., Biradar, M. (2019). Unilateral common carotid artery occlusion and brain histopathology in rats pre-conditioned with sub chronic hypoxia. 7th Chronic Hypoxia Symposium Abstracts. pg 5. Retrieved May 2, 2019. http://zuniv.net/symposium7/Abstracts7CHS.pdf
Gerstein, W. (2019). Endothelial dysfunction at high altitude. 7th Chronic Hypoxia Symposium Abstracts. pg 11. Retrieved May 7, 2019. http://zuniv.net/symposium7/Abstracts7CHS.pdf
Hypoxemia. Cleveland Clinic. Updated March 7, 2018. Retrieved May 9, 2019. https://my.clevelandclinic.org/health/diseases/17727-hypoxemia
Yuki Ikeda has been a professional cyclist for the past 10 years. He’s won titles in both Japan and the US. Interestingly enough, however, he come to Colorado to study at Metro State in Denver in order to play pro basketball. He is now known as an Ultra Mountain Athlete, not only biking, but running races up to 100 miles at altitudes over 10,000 ft. Over some decaf coffee on a warm Sunday afternoon at Gonzo’s in Frisco, he tells me he tried out every semester for the college team and failed. He had never really explored outdoor recreation growing up in Japan, because he had been so focused on a career in basketball.
He started taking some classes on outdoor sports while he was in Colorado, at Metro and then at Red Rocks Community College: rock climbing, cycling, backpacking, kayaking … He ended up staying in Colorado after graduating from Metro. “At that time, I was so into mountain biking,” he says. “I decided to pursue my career in mountain biking.”
He started racing in 2002. It took him five years to accumulate sponsors and become a full-on pro. “After every season, I sent my resume — racing results and what I do — to so many teams [to see if] they [would] accept me or not.”
But he started to get burned out. While he was still improving his stats, he was noticing that he couldn’t maintain the lead against some up-and-coming younger racers. “I was mentally very tired the last couple of years. I was kind of frustrated. Last year, after the season, I was so bummed out, I didn’t want to ride my bike, and I didn’t feel like starting training for the next year, so I stayed away from biking. I didn’t even touch my bike for a month.”
“But I still wanted to do some exercise. I just followed my wife, running, then I kind of joined the local trail running community. They showed me where to go and where to run, and I just loved it. I was so into mountain biking only, I thought doing other sports might cause injuries and effect my career. But it was the opposite.”
His new love for running turned his career around. “Physically, I don’t know [if it has improved my biking] yet, but mentally it helped. Now, my training is still 60 – 70% cycling, but not all the time. When I get on the bike, my brain is still fresh. Before, I rode my bike every day, pushing hard every day. It burned me out.”
Last month, he ran his first ultra running race, 50K. “Last October, I got sore from just running only 5K. Now I an run 50K, so that’s awesome.” He won.
Ultra Training at Altitude
I ask him how he trains for these races. Every summer, he comes to Colorado, staying in Frisco or Breckenridge to train in preparation for a series of races at altitude. It usually takes him 10 days to almost 3 weeks before he can do the same workouts he does at sea level in Tokyo.
Threshold power key. Threshold power is the maximum power you can sustain for about 60 minutes. He has a power meter on his bike that measures the power he exerts in watts. Recently, he has also been wearing a similar device on his shoe for when he runs.
“In Tokyo, my number is 310 watts, but here, it’s almost 270 to 280. I just did a threshold test last week. So that’s almost 10 to 12% lower. But still, if it’s within 10 to 15%, that’s very good for this altitude. But I usually take the test after a week or 10 days after I get here. I cannot push myself hard enough [before that]. Even [if] you’ve adjusted to this altitude, your power number is still lower than at sea level. I feel like I’m weak, but you have to accept it. That’s just how it is.”
His next race is part of the Leadman series, consisting of 5 mountain biking and trail running races in Leadville, Colorado. This next one is 42 km. Originally, the trail takes the runners over Mosquito Pass, which is at over 13,000 ft. But this year, there is still so much snow that the trail has been re-routed, so the runners aren’t sure what to expect. But the race starts at over 10,000 ft.
To train for this, he’s been running and biking six days a week. Every morning, he measures his blood oxygen saturation using a pulse oximeter. The first morning he arrived in Frisco, it was at 92. After a couple weeks of acclimation and training, it’s pretty reliably at 96 every morning.
Yuki claims the most difficult part about running these long races is pacing. His coach encouraged him to run “negative splits”, increasing his speed toward the end of the race. “At my first 50 km race, even though I won it, I could have paced myself better. I just went too hard at the beginning [to] take the lead and paid for it later in the race. I was so trashed after the race, I couldn’t even stand and walk.”
“My coach is saying to be careful about [hitting the wall] at altitude. It’s so hard to recover. It takes almost five times longer than at sea level. I need to pace myself, especially for running 100 miles,” Yuki says, referencing the Leadville Trail Run in August he is also preparing for: 100 miles at altitude. “I’m so excited, but at the same time, I’m so nervous. Even finishing is questionable at this point.”
His secret to acclimating comfortably and quickly is actually movement. He says he feels the affects of the elevation more when he’s sedentary. In order to get more oxygen to his body, he has to get his circulation going. “The first week, I feel better when I exercise than when I just sit [around]. “
Also, beets. And red bell pepper. And arugula.
He eats a limited portion of these every day he’s at altitude. These vegetables provide a lot of nitrates, which your body processes into nitric oxide, facilitating blood circulation. At altitudes over 8000 ft., where you have access to about a third of the oxygen available in the air at sea level, the key to supplementing the oxygen your body requires is increased blood flow. After a certain amount of time, your body starts creating more oxygen-carrying red blood cells to counter the deficit, so getting the blood moving is literally vital.
According to high-altitude growth and development expert Dr. Christine Ebert-Santos, nitric oxide is often the way newborn babies with complications at altitude are treated. Hypoxia (the state of receiving less oxygen than is normal at sea level) causes pulmonary vessels (in the lungs) to constrict. Putting these infants on nitric oxide gas dilates the pulmonary arteries and improves some types of respiratory distress.
There are powders marketed to aid the food version of this nutrition, including BeetElite, Yuki’s product of choice, which he’ll add to his sports drinks in addition to consuming about an ounce of roasted beets. But portion control is also important, as too much nitrate can also have a negative effect on the body.
Yuki is learning that he has to deal with an interesting phenomenon when it comes to his ultra running races: it’s tough on his guts. When it comes to his diet, he doesn’t typically change anything for recovery after a long event. “But I think my guts are more tired, because your body is bouncing so much from running.”
When running these incredible distances, he fuels his body with an energy gel every 20 to 30 minutes while running. “It usually has about 100 to 120 calories. It’s a dense energy. Then you take them for five hours, continuously, so it also tires out your guts. During the race. You have to maintain your blood sugar and keep your muscles moving. My muscles are tired, but also, my intestine and stomach are tired.”
“Even water is hard on my stomach [after running a race]. I’m kinda worried about running 50 and 100 miles. I’m not only worried about my legs, but even my stomach. I’m not used to [consuming] energy for 20 hours, eating and running at the same time.”
In Japan, hot springs and bathing are also a huge, sacred part of the recovery and health ritual. He takes a hot bath almost every day, “especially in winter,” he says. “It helps me to sleep at night.”
The first week he spends at altitude in Colorado, he finds it harder to fall asleep. “I used to take one or two melatonin capsules every night, but it’s hard to tell if it helped. I just go to bed early, like 8 or 9, even if I cannot fall asleep. I just take the time to lay down and recover. [I try to sleep] at least 7 to 8 hours a night, but sometimes it’s hard. If I can’t get that amount of sleep, I usually take a nap after training.”
This may sound obvious, but sleep is when your body does most of its recovery, both mentally and physically. Sleep experts and studies have proven that the body and brain visibly deteriorate after so much sleep deprivation. And at altitude, with less oxygen available to supply a body in constant motion, sleep may be more important than ever.
Yuki isn’t the first high-altitude athlete I’ve spoken to who advocates for a plant-based lifestyle. In a recent blog, skier and duathlete Cierra Sullivan also tells us about how a plant-based diet seems to make a big difference.
“When I used to like and eat animal products a lot, my recovery time was slower than now. It was hard to digest animal fats. I believed that they had a lot of good protein, but it was so hard on your body and digestive system,” Yuki says. “It took time to change my diet, but I now feel more comfortable with my plant-based diet, physically and mentally.”
Live High Train Low
Another recurring theme among high-altitude athletes.
“One of my sponsors has an altitude tent. They leased it to me before the competition, so I used it about a month. I slept in the tent, set at about 3000 m, then I train at sea level. I think it helped a bit, but it might be too short to tell. It tired me [out], though. I think I needed to do it longer before the competition, like, two or three months. I couldn’t train well, because I felt tired all the time. But I think for altitude training, I think this elevation is almost too high. Because you cannot push to your maximum potential. For example, for cycling, I can push up to 1000 – 1200 watts at sea level, but I cannot hit that number here, so I cannot train in that range here. I can lose that high power if I stay longer here. But it depends on your [goal]. My [goal] is winning the Leadman series, that’s why I’ve come here to train.”
This is partly why Yuki will lift weights once a week when training at altitude, “to maintain my high power.” With such limited access to oxygen, athletes up here can’t reach the same “punching power” that they can at lower elevations, so lifting may help maintain that power. “Very short, maybe 45 minutes, once a week, just to maintain. Weightlifting is still supplemental for your specific sport, so I don’t want it to affect my training on my bike or running. For race week, I don’t lift weights, because lifting weights takes time to recover.”
Keeping It Fun
“My trick to keep going — the best way to improve yourself,” Yuki adds, in a final reflection, “is to keep it fun. If you’re not having fun, I think that’s not good. Last year, I almost lost my motivation as an athlete. I almost thought about quitting racing, but I still love the sport. Trail running helped me mentally and physically, and my motivation came back, even for cycling. Having fun is the key to keep going.”
Thank you, Yuki. I completely agree. And best of luck with that 100-mile trail run at 13,000 ft.! Keep track of Yuki’s race schedule, social media and stats at http://yukiikeda.net/
Roberto Santos is from the remote island of Saipan, in the Commonwealth of the Northern Mariana Islands. He has since lived in Japan and the Hawaiian Islands, and has made Colorado his current home, where he is a web developer, musician, avid outdoorsman and prolific reader. When he is not developing applications and graphics, you can find him performing with the Denver Philharmonic Orchestra, snowboarding Vail or Keystone, soaking in hot springs, or reading non-fiction at a brewery.
“I’ve never had a patient with a normal overnight pulse oximetry study,” said Tara Taylor, Family Nurse Practitioner at Ebert Family Clinic. She has been a provider there for a year, after 14 years working as a nurse in the intensive care unit at Swedish Hospital. Of course, the study that tracks oxygen and heart rate during sleep is usually performed on patients with symptoms such as snoring, fatigue, poor-quality sleep, attention deficit, depression, or high blood pressure.
What is normal for healthy adults at altitude? When would sleeping on oxygen help cure or prevent some of these symptoms?Do we even notice when we’re being deprived of oxygen while we sleep?
These are the questions addressed in a new investigator-initiated research trial at Ebert Family Clinic. The catalyst for the study was a conversation between Dr. Christine Ebert-Santos and Annette Blakeslee FNP at the 7th World congress of Chronic Hypoxia in La Paz, Bolivia in February. Annette is the provider for the US Embassy staff at 12,000 ft elevation. State department officials spend months or years on assignment there, and Annette wanted to know when she should be concerned. Local residents living at altitude for generations are adapted, while people living in La Paz and Summit County for months or years are acclimatized but still at risk for conditions caused by the low-oxygen environment.
The study, called “Overnight Pulse Oximeter Study at Three Altitude Sites”, will recruit healthy adults ages 20 to 65 years. Participants will fill out a health questionnaire, take home a simple monitor worn on the finger and wrist to wear during sleep, and return the monitor the next day. Ebert Family Clinic staff will download the data for further analysis. Participants will be notified by a provider regarding the results of their study. De-identified data will be transferred to Excel spreadsheets from which graphs and charts can be generated.
Besides dividing participants into three different altitude ranges between 7,000 and 12,000 feet, data will be analyzed by age groups and symptoms. “Everyone responds to altitude differently,” states Dr. Ebert-Santos. “There are hundreds of chromosomes that affect our ability to adapt. Many studies show the benefits of living in a low-oxygen environment, but a small percent of us will do better sleeping on oxygen. We are hoping this study will establish normal values and suggest who should be evaluated further.” — Dr. Christine Ebert-Santos
For more information, or to become a participant in this sleep study, residents of altitudes 7,000 ft. or above in Colorado for at least 6 months and between the ages of 20 and 65 years old should call Ebert Family Clinic at (970) 668-1616.
Last September, my friend and I decided to go camping. We chose an area close to Silverthorne, Colorado (9,035 ft.) and decided to camp above tree line at around 11,000 feet. Both of us were endurance athletes and had done camping trips at altitude many times without complications. We considered ourselves in great shape and ready for any adventure.
We departed from our home in Fort Collins (5,003 ft.) in the morning and arrived at the trailhead before noon. We were well prepared and had plenty of nutrition in our 40+ lb.-backpacks. The start of the trailhead was at 9,035 ft and we had to hike 7 miles to our destination at 11,000 ft. We were well hydrated, built our camp and went to bed. Both of us had mild edema to our extremities, but nothing that we were worried about as we had experienced these symptoms on multiple hikes to higher elevations in the past.
We spent the next day hiking above tree line, staying hydrated and fueling with high-quality calories. We have learned from personal experience to eat even when we do not feel like it. We both have experienced weight loss of about 5-10 lbs. per week when camping and hiking above 10,000 ft.
We did a 7-mile exploratory hike along the ridge line at 11,000 ft. the next day, again, staying hydrated and consuming plenty of calories. We returned to camp when my partner first mentioned a mild pounding headache. He drank more fluids, had dinner and went to bed.
I woke up at around midnight due to my partner running out of the tent. He vomited once and returned to the tent. Something else seemed off. He did not zip the tent door shut when he returned. He mumbled that his head was hurting and kept his head elevated as it relieved the pain to some degree. A few hours later, he vomited again.
The next morning I proposed that we should pack up camp and hike down the mountain, as he continued to complain of a pounding headache. He refused and wanted to go hike some more. I left the tent site first, walked a few steps and turned around: he was sitting down, staring at the ground. Now I started to really get worried as he was an amazing endurance athlete with a never-ending hunger for adventure. This was not like him.
I decided to pack up the tent, whether he liked it or not. We needed to get off the mountain before his condition worsened.
After many attempts, I was finally able to convince him to come with me, and we started our descent. Between 11,000 ft. and 9,000 ft. we walked slow, as his coordination was slightly limited. As soon as we reached 9,000 ft., he started to improve: he started to walk faster, was more coordinated, and communicated more. By the time we got back to our car, he was back to his normal self, however he still had a lingering headache.
The effects of altitude on his body were very surprising. He demonstrated some classic symptoms of what the high altitude medical community refer to as “HACE”, High Altitude Cerebral Edema: headache, vomiting, confusion, and ataxia (a loss of control of body movement). The experience was unexpected and scary. Cell phone reception is very limited in the backcountry and if his condition would have worsened, this trip could have ended in a very bad situation.
Summit County, Colorado is a beautiful place to explore the outdoors, hiking and camping. I recently had a conversation with an avid outdoorsman who calls Fort Collins (4,982 ft.) his home and enjoys hiking and camping in Summit County at elevations ranging from 9,000 ft – 12,000 ft. He stated that he consistently experiences unwanted weight reduction of around 5-10 lbs. in body weight per week when living in the backcountry at elevations above 9,000 ft.
Is this weight loss related to increased activity without adjusting calorie intake? Could this weight loss be related to exposure to higher elevation and possible changes in metabolism? How can one keep track of calorie-cost and anticipate the inevitable stress on the body at altitude?
Compare your activity level
A GPS or even a pedometer can help measure and compare activity. An increase in miles or steps compared to baseline may require caloric adjustment in order to prevent weight loss. Calorie input should equal calorie expenditure in order to prevent weight loss. It is important to take into consideration that hiking in the mountains usually requires a high level of physical performance due to elevation gain and loss as well as walking on uneven surfaces which result in increased muscle recruitment.
Increased basal metabolic rate (BMR)
According to Dünnwald et al. (2019), exposure to higher altitude increases BMR initially as the body is adapting to the hypoxic environment. The study concluded that increased sympathetic activity and hypoxia may be responsible for the increase in BMR. Due to more extreme exposure to elements such as cold, wind, rain and snow, involuntary shivering may also contribute to an increase in calorie expenditure and should be considered when preparing for the backcountry.
Decrease in appetite
Another factor contributing to possible weight loss may be related to a lack in appetite. Research on the cause of high altitude anorexia is ongoing, however some researchers believe there may be a correlation between a change in appetite-stimulating hormones at altitude. A study by Shukla et al. (2005) found a decrease in total levels of the appetite-stimulating hormone ghrelin, peptide YY, glucagon-like peptide-1, and leptin at initial exposure to altitude. Pre-packaging and scheduling meals while hiking at altitude may aide in the prevention of weight loss during backcountry activities.
Chaudhary et al. (2012) propose that changes in protein turnover in hypoxic environments may be related to muscle wasting, including a decrease in protein synthesis and an increase in protein degradation. To minimize muscle atrophy, it is important to consume high protein foods frequently. Amino acids may also aide in protein synthesis. Packing snacks with high nutritional value can prevent weight loss. Nutrition labels on food items are a great way to identify optimal snacks.
Hiking in the backcountry on a multi-day trip requires preparation. I choose high-calorie foods that taste good, are light to pack, and have minimal waste. I make breakfast and dehydrated meals at home and put them into individual bags that only require me to add water. Making your own dehydrated meals allows you to avoid unnecessary additives. I supplement throughout the day with high calorie snacks. If I have room in my pack, I also add what I call “novelty” backcountry foods, such as cheese and wine – it is important to splurge every once in a while, even if you live in a tent.
Great foods for the back country:
Butter or Coconut Oil coffee: many companies make pre-packaged individual coffee. One cup of butter coffee is around 200 calories.
Perfect Bars: 1 Bar has around 300 calories and 17 grams of protein.
Pro Bars: 1 Bar has 390 calories, they are light to pack and taste great.
Nuts and seeds: easy to pack, great source of healthy fats, calories and protein
Jerky: we make our own elk jerky. It is a great snack throughout the day with healthy protein and added salt.
Apples: It is difficult to get fresh fruit in the back country. Apples are easy to pack, last for a long time and allow you to get vitamins and fiber.
Dehydrated fruits and vegetables: great addition to oatmeal in the morning and your dinner at night. Dehydrated fruits and vegetables are easy to make at home, very light to pack, and you can rehydrate them in the backcountry.
Oatmeal with protein powder: we pre-package oatmeal with dehydrated fruit and a scoop of our favorite protein powder in individual bags. Just add water and you have a fantastic-tasting and calorie-rich breakfast.
Every backcountry excursion should be well planned and it is always better to be over-prepared. It is crucial to be knowledgeable about what foods need to be consumed and when, in order to prevent negative outcomes. Know the distance and elevation changes on your trip, prepare for changes in weather, plan your calories out for every meal on every day, and make a schedule to prevent complications related to nutrition.
Most importantly: enjoy the beauty of the high-elevation backcountry!
Angi Axmann Grabinger is Nurse Practitioner student at the University of Northern Colorado. Angi’s passion in healthcare involves disease prevention and integrative medicine. If Angi is not studying, working or gardening, you can find her exploring the mountains running or hiking.
Chaudhary, P., Suryakumar, G., Prasad, R., Singh, S.N., Ali, S., Ilavazhagan, G. (2012).