Altitude, Acute Mountain Sickness, and Headache
David W. Dodick, MD, FAHS, FRCP(C), FACP
- Headache and acute mountain sickness occur commonly over 8,500 feet above sea level.
- Actions to reduce headaches at high altitude include good hydration, gradual ascent with days of rest and sleep at lower altitude whenever possible.
- Take ASA, furosemide or acetazolamide several days before going to high altitude to avoid headache.
For more than 2,000 years, headache has plagued those who tried to ascend to high altitudes. Headache was so common among travelers along an ancient silk route in Central Asia that a Chinese official named the area "Great Headache Mountain and Little Headache Mountain". Modern evidence that headache occurs frequently at high altitude comes from studies of people living in the South American Andes and from soldiers of the Indian Army who moved frequently between sea level and altitudes up to 6,000 meters in the Himalayas. In addition, headache occurs in almost 50% of the thousands of people who trek, climb, and ski at heights over 3,000 meters (9,900 feet). Even during the Mexico City Olympics held at an altitude of 2,300 meters, migraine headache occurred more frequently than Olympics held at lower altitudes.
Headache may be a prominent symptom in people with chronic exposure to high altitude. In a study of 379 adult men who lived for more than 10 years in Peru at an altitude of 4,300 meters (14,200 feet), nearly half (47%) complained of recurrent headaches, either migraine (32%) or tension-type headache (15%). The occurrence of migraine and tension-type headache increased with age in this group of people, the opposite to that observed at sea level. Because the lungs' efficiency in supplying oxygen to the body declines with age in all individuals, oxygen levels in the blood may decrease even further with advancing age in those who reside at high altitudes. Since migraine occurs more commonly when the blood level of oxygen falls, this might explain why headaches seem to increase with age in those who live at higher altitudes.
We now recognize that nearly one in four people who ascend to 2,600 meters (8,500 feet) above sea level develop symptoms referred to as acute mountain sickness (AMS). Headache is the most prominent symptom of AMS and may be accompanied by other symptoms including:
- Sleep disturbances
- Loss of appetite
The most important variables affecting the incidence of AMS according to studies include an individual's birthplace, acclimatization in the week before the travel, the rate of change in altitude and days of rest while ascending. Rest days were most potent protective variable.
How can you identify with Acute Mountain Sickness headache?
- AMS headache is usually intense, throbbing and is either generalized or in the forehead.
- It develops within 6 hours to 4 days of arrival at high altitude and can last for up to 5 days.
- The headache often worsens with exertion, coughing, straining or lying flat.
- Facial flushing, eye redness, and sensitivity to light may accompany headache.
The headache does not appear to be the result of low blood oxygen (hypoxia) alone because the attack often doesn't begin for hours to days after thriving at the higher altitude. Furthermore, oxygen therapy does not usually relieve the headache. Fortunately, these headaches generally go away after descent to sea level, although in unusual instances the headache may persist for several days to months.
The underlying cause of the headache remains unknown. Swelling of blood vessels has been considered as a potential cause, but not confirmed with experimental studies. Some experts feel that the brain swells with increased pressure within the headache, but no direct evidence exists for this explanation either.
Treatment of Acute Mountain Sickness
High-altitude headache responds to ibuprofen, and can be prevented, at least in some individuals or to some degree, by aspirin, furosemide, acetazolamide (Diamox®) before reaching high altitudes. For acetazolamide 250mg 2x per day (500mg total each day) is possibly more effective than lesser amounts. Because the headaches resemble migraine, sumatriptan has been tried and found effective in some people.
In addition to these medications, there are several tricks to avoiding or limiting the discomfort of adjusting to high altitude for those who are susceptible:
- Avoid dehydration by drinking five 8-ounce glasses of water prior to reaching a higher altitude and while at that altitude.
- If possible, travel to a high altitude should be gradual with rest or minimal activity days to allow your body time to adjust to small, gradual decreases in the amount of oxygen in the air and in your blood.
- Sleep at lower elevations than you play. If you are hiking or skiing at altitudes above 8,500 feet, say in accommodations below 7,500 feet whenever possible.
- For people who have trouble sleeping and breathing at night, particularly if AMA has occurred in the past, use acetazolamide (Diamox®) as a preventive treatment before and during the time spent at the higher elevation.
David Dodick, MD, FAHS, FRCP(C), FACP, is Associate Professor of Neurology, Mayo Clinic, Scottsdale, AZ
Updated September, 2008 from Headache, The Newsletter of ACHE. Spring 2000, Volume 11, Issue 1.