Imagine that you are a mountaineer climbing to the top of a mountain, or an adventurer who wants to photograph glacial lakes. As your altitude increases, your heartbeat begins to accelerate. You’re out of breath, feeling dizzy and nauseous. Instead of enjoying the unique view, a sense of restlessness overwhelms you…
At first, all of these might seem like a natural consequence of the effort you’re exerting, but most likely, you’re experiencing symptoms of high-altitude sickness. Your internal system forces you to stop because it cannot adapt to the changing pressure and unfamiliar oxygen levels. Now is the time to listen to your body and take a break.
What are High-Altitude Sicknesses?
High-altitude sicknesses are health problems encountered during high-altitude activities such as mountain trekking, alpinism, snowboarding, parachuting and wingsuit flying.
These problems, which are associated with low atmospheric pressure and decreasing oxygen levels, occur as a result of the body having difficulty adapting to the conditions at high altitudes. The three most common high-altitude sicknesses are:
Acute Mountain Sickness (AMS)
The most common form of high-altitude sickness is acute mountain sickness, also known as AMS. Symptoms of acute mountain sickness usually begin a few hours after ascending to high altitude. The most common symptoms are headache and nausea.1
Headache is usually the first symptom of acute mountain sickness. In some people, this pain may resemble migraine attacks. These types of headaches are often considered as part of the process of acclimatization to high altitudes. As the body adapts to the environment, the severity of headaches tends to decrease. For some individuals, headaches may be accompanied by nausea. In this case, loss of appetite is likely to occur.
In connection with the decrease in oxygen levels, some people may experience problems such as weakness, fatigue and sleep disturbance. However, these problems generally tend to lose their effect as adaptation is achieved.
High-Altitude Pulmonary Edema (HAPE)
This condition occurs due to fluid accumulation in the air sacs of the lungs. When ascending rapidly to a high-altitude location or when the body fails to adapt adequately to high altitude, blood flow and oxygen transfer can be disrupted. This can lead to fluid buildup in the lungs. Symptoms such as shortness of breath, rapid breathing, blood in the sputum and wheezing are among the signs of high-altitude pulmonary edema.2
High-Altitude Cerebral Edema (HACE)
Characterized by swelling of brain tissue, HACE (high-altitude cerebral edema) is a condition that develops when the body fails to adapt to high-altitude atmospheric conditions, much like HAPE (high-altitude pulmonary edema). It occurs due to fluid accumulation in brain tissue as a result of blood vessel dilation. The most common symptoms of HACE include severe headache, vomiting, visual hallucinations and coordination disturbances.3
Compared to acute mountain sickness, both HAPE and HACE are very serious complications. Both require immediate medical attention.
Causes of High-Altitude Sicknesses
The main cause of high-altitude sickness is the decrease in atmospheric pressure and oxygen levels at high altitudes. At sea level, the oxygen pressure in the atmosphere is approximately 101325 Pa. However, at an altitude of 3000 meters, this pressure drops to around 68652 Pa. It takes time for the body to adapt to this pressure and oxygen level. If this adaptation process is not carried out slowly enough, symptoms of acute mountain sickness such as headache, nausea and weakness may occur. Acute mountain sickness is typically mild to moderate in severity, but if not treated with appropriate methods, it can escalate into more serious conditions.4
In addition to low atmospheric pressure and insufficient oxygen levels, temperature can also be counted among the factors affecting high-altitude sicknesses. Since the temperature is generally low at high altitudes, it becomes difficult to maintain body temperature. This condition may affect the airways and cause asthma and similar respiratory diseases to aggravate.5
| Altitude | Temperature | Atmospheric pressure | ||
| Meter | Feet | °C | °F | Pa |
| 0 | 0 | 20 | 68 | 101325 |
| 1000 | 3281 | 13,5 | 56,3 | 89798 |
| 2000 | 6562 | 7 | 44,6 | 78933 |
| 3000 | 9843 | 0,5 | 32,9 | 68652 |
| 4000 | 13123 | -6 | 21,2 | 59156 |
| 5000 | 16404 | -12,5 | 9,5 | 50391 |
| 6000 | 19685 | -19 | -2,2 | 42214 |
| 7000 | 22966 | -25,5 | -13,9 | 34943 |
| 8000 | 26247 | -32 | -25,6 | 28269 |
2000 – 3000 meters — In this altitude range, atmospheric pressure is lower than at sea level. However, for many people, there are no serious symptoms.
3000 – 4000 meters — The amount of oxygen and atmospheric pressure decreases significantly. Symptoms of acute mountain sickness (AMS) begin to appear at this altitude. Mild symptoms such as headaches, nausea, fatigue, sleep problems and dizziness may occur.
4000 – 5000 meters — The risk of acute mountain sickness (AMS) increases. Symptoms of hypoxia (oxygen deficiency) and coordination problems may occur. Due to low humidity levels and increased breathing rate, the body loses more fluids. Protective clothing is necessary to guard against cold weather conditions as the risk of hypothermia begins.
5000 – 6000 meters — The risk of both high-altitude cerebral edema (HACE) and high-altitude pulmonary edema (HAPE) emerges. Severe symptoms such as shortness of breath, bloody sputum, confusion and hallucinations may appear. It is critical to descend to a lower altitude as soon as possible when symptoms appear. Regular health checks should be conducted, and readiness for emergency intervention is essential.
Above 6000 meters — The risk of hypothermia is extremely high. To reduce the risk of frostbite, clothing resistant to extremely cold weather conditions is necessary. Complications from oxygen deficiency can result in loss of consciousness, coma and even death. The body cannot maintain normal functions at these heights. Continuous oxygen support is vital. Those climbing above 6000 meters must be physically and mentally well-prepared and have the appropriate equipment.
Reduction of Symptoms and Prevention of Diseases
The most effective way to prevent high-altitude sickness and reduce symptoms is to gain altitude slowly and in a controlled manner. Therefore, professional mountain climbers make camp at regular intervals to allow their bodies to adapt to changing atmospheric conditions. The general recommendation is to take a night’s rest every 300-600 meters after reaching an altitude of 2500 meters. However, this depends on many variables such as the climber’s age, fitness level, psychological state, general health condition, medications and supplements and dietary habits.
Another factor that increases symptoms is dehydration. Under high-altitude conditions, the body loses more water than usual, which can exacerbate symptoms of high-altitude sickness such as headaches, dizziness and fatigue. Therefore, it is very important to consume adequate amounts of fluids during high-altitude activities. Especially, consuming drinks that maintain electrolyte balance helps keep the body’s hydration levels stable.
If the symptoms of acute mountain sickness (AMS) are mild, rest and adequate fluid intake are usually sufficient. However, if the symptoms are severe or worsening, immediate intervention is necessary.
The most effective treatment is to descend to a lower altitude as soon as possible. This allows the body to receive more oxygen and helps alleviate the symptoms. If descent is not possible, oxygen support can be provided using portable oxygen tanks or oxygen concentrators.
In severe cases, active ingredients such as acetazolamide or dexamethasone can be effective in alleviating and preventing symptoms. Acetazolamide helps the body acclimate to high altitude more quickly, while dexamethasone reduces inflammation, lowering the risk of cerebral and pulmonary edema.4
The use of these medications is not recommended without the advice and supervision of a doctor. Active ingredients like acetazolamide and dexamethasone can have serious side effects. Unconscious use of medication can disrupt the body’s natural responses and cause more serious complications. Therefore, individuals experiencing high-altitude sickness or similar health issues should consult a healthcare professional before using such medications.
- Maggiorini, M., Bühler, B., Walter, M., & Oelz, O. (1990). Prevalence of acute mountain sickness in the Swiss Alps. British Medical Journal, 301(6756), 853-855[↩]
- Aksel, G., Çorbacıoğlu, Ş.K., & Özen, C. (2019). High-altitude illness: Management approach. Turkish Journal of Emergency Medicine, 19, 121 – 126[↩]
- Hüfner, K., Falla, M., Brugger, H., Gatterer, H., Strapazzon, G., Tomazin, I., … & Fusar-Poli, P. (2023). Isolated high altitude psychosis, delirium at high altitude, and high altitude cerebral edema: are these diagnoses valid?. Frontiers in Psychiatry, 14, 1221047[↩]
- Imray, C., Wright, A.D., Subudhi, A.W., & Roach, R.C. (2010). Acute mountain sickness: pathophysiology, prevention, and treatment. Progress in cardiovascular diseases, 52 6, 467-84[↩][↩]
- Seys, S.F., Daenen, M., Dilissen, E., van Thienen, R., Bullens, D., Hespel, P., & Dupont, L.J. (2013). Effects of high altitude and cold air exposure on airway inflammation in patients with asthma. Thorax, 68, 906 – 913[↩]