Altitude medicine is a branch of mountain medicine that deals with the health effects of high altitudes on humans. This includes altitude sickness, which can occur at high altitudes if acclimatization is inadequate and can be life-threatening in severe cases.

In this article, you will find out why caution is required even on family excursions to the Jungfraujoch, and how women and men react differently to stays at high altitudes.

You have experience with hiking in high mountain regions. How did you get into mountaineering?

In college, I started climbing, ski touring and mountaineering out of a fascination. Then I met my husband, who was also a mountaineer. We started a family and took the children with us everywhere. We also went with them to Everest Base Camp for example and lived there at 4200m for three months. We treated people who were sick at high altitudes and offered family medical treatment for the local population.

I find mountaineering something absolutely beautiful and could no longer live without it. Even as a 60+, the enthusiasm has hardly diminished, except for maybe the musty, crowded camps that you visit when mountaineering.

Which peaks have you already conquered and what exactly fascinates you about high mountains?

There are many around the world, including the Matterhorn, the Weisshorn or the Biancograt in Switzerland, Kilimanjaro in Africa or Denali (formerly Mount McKinley) in Alaska. What fascinates me? Of course the mountains themselves, the nature that shows us how small and also helpless we are in this powerful nature, the adventure, and lastly the activity itself that teaches us where our limits are. Sometimes mountaineering feels like a drug to me - some drink alcohol, others climb high peaks.

Health risks can certainly be understood as limits. Among them is altitude sickness. What is that exactly?

Altitude sickness is a symptom complex that can be distinguished between 3 different conditions:

1. acute mountain sickness, also called AMS
2. high altitude pulmonary edema, also called HAPE
3. and high altitude cerebral edema, also called HACE

By far the most common is AMS. You can imagine a hangover after a boozy evening with too much alcohol: You feel floppy, tired, a little dizzy, you feel a little "woozy," you have no appetite, and you suffer from a headache. That's exactly what AMS feels like.

Much rarer, but much more dangerous are HAPE and HACE. These are dangerous conditions that are life threatening if not treated immediately. HAPE is pulmonary edema, which as the word explains, is accompanied by water in the lungs. This results in a lack of oxygen flow. Oxygen is important for maintaining the function of every single cell in the body. Symptoms of HAPE include fatigue and shortness of breath- people simply can't take any more.

HACE is the counterpart to the brain, so an accumulation of water in the brain. This, too, leads to undersupply of oxygen to the brain, but also to increased intracranial pressure. When water suddenly accumulates within the skull to an increased degree, there is too little room for the brain itself, and there is increased pressure. This is accompanied by severe headaches, nausea, vomiting, and impaired consciousness and is, as mentioned, life-threatening.

Who is at risk?

Actually quite simple. The following applies to all three diseases: if you ascend too high too quickly, you will become ill. AMS starts at an altitude of 2500m. This altitude is reached in many mountain regions of Switzerland. HAPE and HACE usually only occur at higher altitudes of 4000m and above, i.e. rather on expeditions in higher areas of the world, such as the Himalayas, Kenya, Aconcagua, Denali and Elbrus, i.e. everywhere where the altitude is far above 4000m.

There is a risk for everyone who disregards the rules. Our rules to prevent altitude sickness are: once you're at 2500m, do not ascend more than 300-500m per day. The decisive factor is the sleeping altitude. For all diseases, there are people who are particularly susceptible. The reasons for this have not yet been fully researched, but in principle, once you get altitude sickness, you will get altitude sickness again. This risk of recurrence is particularly pronounced in the case of HAPE.

How dangerous is altitude sickness?

AMS is harmless in mild form but in severe disease it can progress into HACE, in which case it becomes life-threatening. HAPE, once present, is also life-threatening.

To what extent does age or pre-existing conditions play a role?

Age does not play a role in this sense. The above-mentioned risks exist equally for all age groups. Many chronic diseases, on the other hand, naturally increase the health risk at high altitudes. This is a vast area but basically it can be said that chronic diseases, in which oxygen plays an important role, carry a particularly high risk.

Does physical fitness matter?

Yes and no, there are controversial opinions on this. Fitness does not play a role in large epidemiological studies. Nevertheless, there are studies that show that fit climbers or trekkers are more likely to get sick at altitude than less fit climbers. This probably has to do with the fact that fit climbers are more likely to overexert and push themselves to their limits. It is extremely important to give the body time to get used to the unusual altitude - this is called acclimatization.

We are a marvel of nature. Our body has various mechanisms in store to optimize survival in an unfamiliar environment. So when the partial pressure of oxygen drops at altitude, the body cannot take in as much oxygen from the environment as it would need. In acclimatization, therefore, the body begins to breathe more, the kidney adjusts the acid balance, and more red blood cells are produced. The whole system is rearranged so that more oxygen can be absorbed into the blood and transported to the tissues.

But this takes time and the body must not be overstressed in these situations. Of course, it is always good to bring a high level of fitness, so there are reserves for the considerable physical effort. However, macho behavior should be left at home during the acclimatization phase.

Couldn't it also be the case that more fit people climb to high altitudes and thus more fit people get sick?

This is also possible, and would certainly have to be investigated in more detail.

Why is the sleeping height and not the height at which you stay during the day the decisive factor?

The development of altitude sickness takes time, certainly 4 hours and more, until it occurs. So, climbing higher in the short term, for example a day trip to the Jungfraujoch, has no effect. But again: it is important not to overtax the body in the process.

What should you do when you get sick?

If the AMS is mild or moderate, a day of rest can help. If the condition does not improve, descent must be made until the symptoms resolve. A severe AMS must be treated, and you have to descend immediately. Often 500-1000 meters of descent is sufficient in the Alps, but this depends on the altitude at which the condition occurred. HAPE and HACE are life threatening, must be treated immediately and whenever possible a passive descent is essential. Passive because this does not further stress the body and deprive the body of oxygen due to the effort of the descent.

Can altitude sickness be prevented with medication?

Yes, it can. Especially for people who get sick every time they go up to altitude. The drug of choice for AMS is Diamox, a drug that increases respiration and interferes with the acid-base balance of the body. For HAPE, there is nifedipine, and for HACE, dexamethasone. For all medications, however, a consultation with a specialist is needed; they cannot simply be bought at the pharmacy without a prescription.

Another form of prevention is pre-acclimatization. For this, you have to sleep at high altitudes at a comparable altitude in the 1-2 months before the expedition. The longer you do this, the better you are acclimatized. Not too much time should pass between acclimatization and expedition, because you can lose the acclimatization again when you descend.

What should be in an emergency first-aid kit for a high-altitude hike?

For non-professionals, nothing special is needed, perhaps a painkiller, which can then be used for headaches. However, if you are traveling to areas where a doctor will not be readily available, you should get a travel medicine consultation before traveling. There you can get one of the drugs mentioned above, but also an antibiotic for bacterial infections, and of course its always a good idea to check your vaccination status.

In 2005, you co-published an interesting paper, «Medical Recommendations for Women Going to Altitude»^[1]. You found that there are quite a few differences between the sexes in terms of altitude sickness and acclimatization. Can you tell us something about that?

We are in the process of revising these recommendations, as much of the research is now better understood. This year and next year we will publish some research results on this topic. Basically, there are no differences between women and men in terms of acclimatization, AMS and HACE. However, HAPE clearly occurs more often in men than in women. We do not yet know why. Part of it may be related to the fact that women still climb high mountains less frequently than men. Perhaps macho behavior in men also plays a role, and there may also be physiological differences. We simply don't know yet.

You've also found that going up into the high mountains can have an effect on the menstrual cycle. How so?

Mountaineering is a stress for the human body. The menstrual cycle is very sensitive to stress. In other words, it gets confused. Often menstrual bleeding stops because the body saves energy where it can be easily saved. The stress is not only due to the oxygen deficit when climbing to high altitudes, but also due to traveling in general, time changes, cold, physical exertion, a different diet and so on.

Something else that is very important: no menstruation does not mean that you cannot get pregnant. Therefore, you must use contraception even if your periods stop. And no menstruation does not mean that it cannot suddenly occur again. You have to be prepared for that. Menstruation can be a challenge, especially on long expeditions in the high mountains, where you sleep in tents and the hygiene situation is difficult without access to running water.

Apparently hormonal contraception has an impact on the risk of thrombosis at high altitudes?

Menstruation in hygienically critical situations is a "necessary evil", if I may say so. One can stop it with a contraceptive pill, which one then simply takes during the entire time of the stay at altitude. Different pills have different compositions of estrogen and progesterone, the market is huge. It has been seen in large epidemiological studies that certain contraceptive pills carry a different risk of thrombosis depending on their composition, incidentally quite independent of the altitude of stay. Although there is always a risk of thrombosis when taking the pill, nowadays it can be assumed that the pill with the lowest possible risk is always prescribed.

In general, regarding the risk of thrombosis at altitude, it can be said that if someone has been taking the pill for years, there is not suddenly an increased risk of thrombosis when this person goes up into the high mountains and continues to take the pill. In addition, other factors can also influence the risk of thrombosis in the high mountains, such as the cold, the thickening of blood due to the increased production of red blood cells or dehydration.

Apparently, iron levels can affect acclimatization. What does that mean?

Actually, it's quite simple. Iron is an important component of red blood cells. Iron is, so to speak, the carrier substance for oxygen in the blood cells. If iron is missing there, the transport of oxygen from the lungs to the tissues can no longer take place optimally, the transport is disturbed. It is therefore important, especially for pre-menopausal women (who often suffer from iron deficiency due to regular bleeding), that they start their journey with sufficient reserves. A brief check with your family doctor is advisable here, especially before longer trips to high altitudes. For short-term stays, a possible deficit of iron plays a minor role.

What other risks should not be forgotten when hiking in high mountains?

Accidents of any kind are probably the greatest risk. Today, an infinite number of people climb high mountains, and among them are also many who do so more or less unprepared and "mindless". They don't have good clothes against the weather, they don't have good shoes, they don't have a bivouac bag against the cold, they don't have emergency provisions if they get stuck somewhere, they don't have enough liquids with them, they don't know the emergency call, and they can't judge the terrain for dangers.

There are moments of danger without end and many amateur mountaineers underestimate them in the high mountains. Good preparation is therefore an absolute "must". Acquiring all the good tricks in a mountaineering school would be an ideal alternative, wouldn't it?

Of course, you've also published quite a bit on children in high mountains. What are the most important takeaways here?

Yes, you don't always have to think of long expeditions in the Himalayas when you think of altitude sickness because high peaks are very easy to reach in Switzerland thanks to all the mountain railroads and are also popular family destinations. For example, a family trip to the Jungfraujoch with an overnight stay in the Mönchsjochhütte already requires appropriate preparation because this is located at over 3500m. Parents are responsible for acclimatizing their children so that they do not fall ill.

We conducted one of the largest studies with children and adolescents on Jungfraujoch. There we found that children and adolescents were no more susceptible to altitude sickness than adults. So there are no significant differences. Or to put it another way, children get altitude sickness just the same. For me, it is important to protect them from this as much as possible. This means following the guidelines of acclimatization: from 2500m, do not add more than 300-500m of sleep altitude and take a rest day every 3-4 days. And in addition: Challenge children, but don't overchallenge them. The mountains should be a positive experience, not a drudgery with altitude sickness. There is a good article on this that we wrote a few years ago, everything in it still applies today.

Are there any other issues, organizations or projects you'd like to bring attention to?

Yes, there is a very recent publication by Peter Hackett and David Shlim, two of the original scientists on altitude sickness, who conducted the first major epidemiological studies. For those who would like to learn more about high altitude travel and altitude sickness, I recommend their chapter in the CDC Yellow Book.

Additionally, I am part of a group of about 10 mountaineering women from different countries around the world, who are scientifically active and carry out a project under the label of the UIAA (Union Internationale des Associations d’Alpinisme^[2]), in which mountaineering women are taken into focus. We are currently in the process of writing articles on various topics, including those specific to women such as pregnancy, menopause, contraception, and dealing with menses while mountaineering. We are also working on chapters on gender differences in altitude sickness, nutrition, frostbites and fatalities in the mountains. The first articles will be published later this year, and a non-expert version of each scientific publication will also be published on the UIAA website.

What a great project! We are looking forward to the upcoming publications. Thank you very much for the interesting interview.

For those interested in a personal travelogue, check out the first episode of our "Wanderlust Chronicles," in which our Business Manager Jenny Crawford recounts her trip to Peru, during which she became hopelessly altitude sick. Click here to read the article.

Interview: Cécile Rasi

^[1]  Medical recommendations for women who go to altitude: Medical Recommendations for Women Going to Altitude. A Medical Commission UIAA* Consensus Paper.

^{[2]  The UIAA is a worldwide organization of medical professionals and experts in the field of altitude. UIAA – International Climbing and Mountaineering Federation}