Monthly Archives: July 2019

Acclimation, Health, High Altitude, Mountaineering

Muscle Atrophy in Visitors at High Altitude

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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). 

References

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.

2. McKinnell IW, Rudnicki MA. Molecular Mechanisms of Muscle Atrophy. Cell Press. 2004;119:907-910.

3. Bonaldo P, Sandri M. Cellular and molecular mechanisms of muscle atrophy. Disease Models & Mechanisms. 2013;6(1):25-39. doi:10.1242/dmm.010389.

4. Rathor R, Suryakumar G. Muscle Atrophy at High Altitude. Journal of Clinical and Molecular Endocrinology. 2016;1(3):1-2. doi:10.21767/2572-5432.10018.

5. Chaudhary P, Suryakumar G, Prasad R, Singh SN, Ali S, Ilavazhagan G. Effect of acute hypobaric hypoxia on skeletal muscle protein turnover. Al Ameen Journal of Medical Science. 2012;5(4):355-361.

Acclimation, Health, High Altitude, Medicine, Mountaineering

Altitude and the Brain

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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.

References:

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.