Chronic Mountain Sickness

Avinell Abdool


Chronic Mountain Sickness (CMS) is a pathological finding that is commonly found amongst individuals that have taken up permanent residence in high altitude environments (altitudes of over 8,200 feet)1. Clinical manifestations of CMS include but are not limited to the following1;

  • HA
  • Dizziness
  • Tinnitus
  • Breathlessness
  • Palpitations
  • Sleep Disturbances
  • Fatigue
  • Loss of appetite
  • Confusion
  • Cyanosis
  • Dilation of veins


CMS is the outcome of progressive loss of ventilation rate, which subsequently results in hypoxemia and polycythemia2. Polycythemia is defined as by excessive erythrocytosis (EE; Hb >/= 19g/dL for women and Hb >/= 21 g/dL for men) which along with a hypoxic environment can result in pulmonary hypertension2. In advanced conditions of Chronic Mountain Sickness there can be cor-pulmonlae and congestive heart failure2 .

A study was conducted in the University of San Diego by Dr. Gabriel Haddad that researched the adaption of the Peruvian population in high altitude conditions3. It was found that CMS is highest in the Andeans (approximately 18 %), lesser in Tibetans (1%-11%) and completely absent in the Ethiopian population3. From these data points it appeared that there was was a genetic correlation between CMS sufferers and ethnicity3. In addition, this finding added another factor that mystified the conclusive pathogenesis of CMS3. By understanding exact pathogenesis of CMS, it would not only benefit those who are at potential risk for the disease but also those living at sea level, where hypoxia plays a role in certain pathology ( such as stroke, cardiac ischemia, Obstructive sleep apnea and Sickle Cell Disease)3 .

A cohort of 94 individuals were gathered and were equally categorized into CMS and non CMS subjects3. These individuals originated from Cerro de Pasco, which has an elevation of greater than 14,000 feet3. Genetic tools and a custom algorithm were utilized and the researchers identified 11 regions on the genome that contained 38 genes that proved to be statistically significant3. Nine of the eleven genes were tested in fruit flies in hypoxic experiments3. The experiment consisted of fruit flies that had these genes and ones that did not have the genes3. It was concluded that individuals with these molecular adaptions were better able to adapt to physiological stress such as hypoxia when compared to individuals that did not have this adaption3. The results of this study allowed researchers to better understand the correlation between genetics and individuals who strive in hypoxic environments3.



Figure 1- D.melanogaster (fruit fly)3



Figure 2-Cerro de Pasco3




  1. Villafuerte FC, Corante N. Chronic Mountain Sickness: Clinical Aspects, Etiology, Management, and Treatment. High Altitude Medicine & Biology. 2016;17(2):61-69. doi:10.1089/ham.2016.0031.
  2. Chronic mountain sickness and high altitude pulmonary hypertension. High Altitude Medicine and Physiology 5E. 2012:333-346. doi:10.1201/b13633-23.
  3. Stobdan T, Akbari A, Azad P, et al. New Insights into the Genetic Basis of Monges Disease and Adaptation to High-Altitude. Molecular Biology and Evolution. 2017. doi:10.1093/molbev/msx239.

Hypertension at Altitude

Will my blood pressure be impacted when I travel to high altitude?
It is not uncommon for lowland visitors with a history of high blood pressure to
experience higher blood pressure at altitude. This can occur even if blood pressure is well
controlled with medication at sea level. However, only a small percentage of these people will
experience unusually unstable blood pressure at altitude. Increased blood pressure at altitude
usually returns to baseline after 1-2 weeks at altitude.
So why does this happen?
One explanation is due to the higher levels of adrenaline in your body due to lower oxygen
levels causing increased heart rate in attempt to increase oxygen circulation throughout the body.
This mechanism supports the findings that increased blood pressure will normalize after 1-2
weeks at increased elevation.
How can I safely plan a trip to high altitude if I have hypertension?
In general, it is unnecessary to change your blood pressure medication dosage before or upon
arrival to elevation. Increasing dosage could result in dangerously low blood pressure upon
returning to low altitude. However, if you are experiencing symptoms from your high blood
pressure such as headache, dizziness, chest pain, or shortness of breath, you should seek medical
treatment. It is also recommended to bring your own blood pressure monitor on your trip. If your
blood pressure rises above 180/90 you are at risk of entering a state of hypertensive urgency and
if it rises above 200/100 this can cause a hypertensive emergency where end organ damage is
possible. In either condition you should seek medical advice whether from your Primary Care
Physician or the Emergency Department if blood pressure is dangerously high. Unfortunately,
there is little information available about the treatment of significantly elevated blood pressure
that is secondary to a quick ascent to elevation and will likely be managed similar to a
hypertensive crisis at sea level with the use of an anti-hypertensive medication chosen by your
healthcare professional. The use of supplemental oxygen, especially at night can also reduce
symptoms and lower blood pressure in some visitors and residents in the mountains.

Written by Grace Murk, PA-S

1. Andrew M. Luks. High Altitude Medicine & Biology. March 2009, 10(1): 11-
2. Institute For Altitude Medicine (2017). Altitude and Pre-Existing Conditions. [online]
Institute For Altitude Medicine. Available at:
pre-existing- conditions/ [Accessed 15 Oct. 2017].
3. Handler J. Altitude-related hypertension. J Clin Hypertens (Greenwich). 2009;11:161–165.
4. Gilbert-Kawai E, Martin D, Grocott M, Levett D. High altitude-related hypertensive crisis
and acute kidney injury in an asymptomatic healthy individual. Extreme Physiology &
Medicine. 2016;5:10. doi:10.1186/s13728-016- 0051-3.