Chronic Mountain Sickness: Losing Acclimatization to Moderate Altitude

What This Post is About:

I am writing this post in hope of helping others who may experience the same thing I am, and giving information to others who may be considering undertaking the same adventure. Some of the information may be a little bit technical, but what I am aiming for is to distill medical research and terminology into terms that an intelligent lay person can understand; I ask that those with medical knowledge and training forgive me if I oversimplify occasionally.

Chimborazo

 

 

I love the moderate-altitude city of Cuenca. It is beautiful, walkable, lively, culturally and architecturally rich, full of life and joy. However, after living here for 10 months, my impressions of this beautiful city are overshadowed by sensations of fatigue and pain. Some of my more dedicated readers may recall the post in which my doctor found gout. As it turns out, my uric acid  continued to climb despite the lifestyle changes I made to combat it. Additionally, repeated re-checks of my liver and kidney enzymes showed signs of ongoing low-level metabolic stress despite my giving up NSAIDs and alcohol.

Altitude Sickness

Finally, one day, I sat across from my MD, Dr. Elizabeth Cabrera, and said, “I’ve researched liver enzymes and altitude, kidney function and altitude, uric acid and altitude, and it all comes down to one thing.”
She spoke at the same time I did: “Altitude.”

“I had no idea,” I said, “that it affected the body’s metabolism so completely. I figured adapting to altitude was like adapting to exercise: your body increased its oxygen uptake to be more efficient, and then as long as you continued to live at altitude, you stayed adapted.”
Dr. Cabrera, being a fluent English speaker, has a large proportion of patients who are lowlanders transplanted to altitude. She explained that these types of problems are not uncommon among immigrants like me or even native highlanders, and the locals have a name for them, mal de montaña but that they can usually be controlled with medication. I had already had a potentially life-threatening reaction to one medication, allopurinol, so I was even more reluctant than I usually am to accept the idea of having to take a medication, or multiple medications, every day just in order to live a normal life. I dove into the National Library of Medicine database to find what peer-reviewed scientific materials had to teach me about the problems I was facing.

What is High Altitude, Anyway?

The first thing I discovered was that I needed to use the correct terminology. Searching for “Altitude” combined with any health term brought up tens of thousands of articles, but more than 90% of them were about acute altitude illnesses like AMS (Acute Mountain Sickness), HACE (High Altitude Cerebral Edema), or HAPE (High Altitude Pulmonary Edema); these are very acute conditions which develop soon after ascending to altitude. Some people develop these conditions immediately on visiting Cuenca’s altitude, but I had (as I thought) passed that test and acclimatized nicely.

As I read the abstracts, I noticed that the altitudes they were discussing varied widely, as did their definitions of what constituted “high” and “moderate” altitude, so I prepared a handy chart based on different web-based reference sources as well as NLM-sourced peer-reviewed articles (metric values converted roughly to feet):

High Altitude? Or Moderate Altitude?

 

As you can see, one source’s “moderate” altitude may be another source’s “high” altitude, which makes searching for information even more challenging. This is particularly true when looking for information about life at the altitude of 8,300 feet, or 2,500 meters, which falls at the border between Moderate and High cutoffs, depending on the source.

Eventually, I wound up with 80 articles which had some bearing on residence at 8,000 feet, more or less. All those documents are archived for easy access here, but for those who may lack the expertise or the patience to read through them, let me summarize.

Basics Effects of Altitude: Overview

The pressure of the surrounding air decreases as you climb to high altitude further away from the Earth’s surface. Think about a stack of cement blocks 24,000 feet high. Obviously, the pressure on the bottom block is much higher than the pressure on the top block (in fact, if you succeeded in stacking blocks so high vertically, the bottom blocks would undoubtedly be crushed to powder).  The same thing is true of air (or water, but that relates more to diving, not our topic here). At 8,000 feet elevation, the pressure of the air around you is just 75% of that at sea level. At 18,000 feet, it’s about half.  The thing to remember is that, because gases don’t hold a shape, that pressure is applied everywhere the air touches: including inside your lungs. That means that the pressure squishing oxygen into your bloodstream when you are living at 8,000 feet is a fraction of the pressure at sea level.

Fortunately, your body has a number of mechanisms to keep the oxygen level in your blood stable at 95% or higher. As soon as you reach an altitude where the oxygen level drops in the blood, the body begins to produce powerful hormones, including ANP and EPO from the kidneys, which increase the oxygen-carrying capacity of red blood cells and begin to lower the overall blood volume so that blood cells are more concentrated. At the same time, the carotid body in the neck and the chemoreceptors in the brainstem sense the decrease in oxygen and increase in carbon dioxide, and they send signals to the sympathetic nervous system to increase the pulse and breathing rate; the carotid body also signals the adrenal glands to produce more epinephrine (which increases breathing and pulse rate) and also cortisol (which has a longer-term effect of increasing blood pressure and decreasing the inflammation which can damage oxygen-starved tissues).

Acute Mountain Sickness: HACE and HAPE

HAPE (High Altitude Pulmonary Edema) results when the amount of blood passing through the lungs is so large that the lungs cannot handle it. The heart keeps pumping more blood to the lungs to try and get more oxygen, and the pressure in the pulmonary artery builds up into the tiny capillaries of the lungs and causes them to burst.  HAPE occurs within the first few days of reaching high altitude. HAPE can be a medical emergency; milder cases can be treated with inhaled oxygen until the person adapts, and drugs can be used to reduce edema and inflammation in moderate cases, but the only way to treat more severe cases is for the patient to be transported to a lower altitude on an urgent, emergency basis. Untreated severe HAPE can be fatal.

HACE (High Altitude Cerebral Edema) also occurs within the first few days of ascent.  The blood vessels of the brain enlarge in everyone at altitude to carry more oxygen to the brain’s critical, oxygen-gobbling grey matter. However, in people who develop HACE, the blood carried to the brain is more than the capillaries can handle, and thousands of these tiny blood vessels begin to burst, causing stroke-like effects.  Again, mild cases can be treated with rest and medical oxygen, and drugs can be helpful, but severe cases can be life-threatening and the person must descend as soon as possible to avoid brain damage.

No one has found a reliable test to predict who will develop HACE or HAPE, which together are included under the umbrella term of AMS, or Acute Mountain Sickness.  People over 50 are at lower risk; women are at less risk than men. AMS also is used to denote the milder symptoms which affect the majority of people who ascend to altitude, including headache, breathlessness on exertion, diarrhea, frequent urination, lack of appetite, and a craving for sweets. Many people find that chewing the raw coca leaf or drinking coca tea, freely available in Ecuador (and much milder than refined cocaine) can help with AMS.

Acclimatization Over Weeks and Months

Fluid loss

The hormones produced by your body in response to lower oxygen pressure include several which cause increased urine production. The effect is to lower your blood volume, so that you will have more oxygen-carrying red blood cells in every drop of blood. Thus, mild diarrhea and increase in urination are common annoyances in the first few weeks at altitude. Urine production gradually decreases, but it never returns all the way to normal.

Vulnerability to Cold

The increase in concentration of blood cells makes it more difficult for blood to get through constricted capillaries in your extremities. At the same time, the hormones produced by low blood oxygen make those blood vessels constrict more easily. Cold hands and feet are the result.

Lower blood sugar and reduced appetite

Burning sugar for fuel stimulates you to inhale more oxygen than burning fats or proteins. Therefore, the body shifts towards burning sugar preferentially at high altitude. Diabetics often find their glucose control is better and their doctors may reduce their medications accordingly. People in general tend to crave sweets, especially at first. This is why, if you move to Cuenca, you will notice people sucking on sweets, popsicles, and ice cream everywhere you look.  On the other hand, greasy foods tend to lose their appeal. The loose bowels and vascular headache also come with some nausea, which lowers the appetite even more.

Greater effort to achieve the same physical work

Even after acclimatizing to living at high altitude, the body’s muscles do not get as much oxygen at maximal uptake, so they don’t produce as much power in low-oxygen conditions as they do at sea level. Therefore, the amount of energy burned to perform a given task, like walk a mile at a set speed, is greater at higher altitude than it is at sea level.

Men lose more weight than women

The overall result of these changes, especially weight loss, is stronger in men than in women, because of the effect of estrogen and progesterone. This is why the typical lowland man who moves to high altitude loses 7-12 pounds and the typical woman loses 4-6 pounds.

Men and women, incidentally, both tend to have higher levels of both testosterone and thyroid hormone at altitude.

How Chronic Mountain Sickness Can Develop

Heart rate and blood pressure

The body shifts over the first weeks or months of living at high altitude, from producing a high heart rate using epinephrine (adrenaline), to producing higher blood pressure using cortisol and higher heart rate using elevated free thyroid hormone levels. These have a similar effect of increasing the total circulation of blood, but the cortisol and thyroid hormone are longer-acting hormones, creating a more stable effect. Dr. Cabrera said that a typical lowlander will have blood pressure at least 10 points higher after living a while in Cuenca.

When mal de montaña develops in earnest,  the backup in lung circulation can stimulate the heart to generate higher blood pressure overall. One day I measured my unmedicated blood pressure at 168/110 in Cuenca the morning. I rode into Guayaquil, at sea level, and measured my blood pressure at lunchtime; it was 125/74!

The bad news about altitude-related weight loss

Unfortunately, much of the weight loss at altitude is muscle mass. Partly due to the loss of appetite for protein, and the general weight loss, 10-20% of muscle mass may be lost in athletes after 4-6 weeks at altitude, leading to the current maxim in altitude training of “train high, sleep low”. I could not find any documentation as to whether or not that lost muscle mass is usually recovered with exercise after longer time periods at altitude.

Effect on cholesterol and triglycerides

The liver, lacking oxygen at high altitude to convert fats to other substances, begins to synthesize triglycerides and cholesterol, so triglyceride levels rise a good bit and total cholesterol and “bad” LDL cholesterol tend to increase; at the same time “good” HDL cholesterol, which has more protein in it, tends to decrease.

Effect on Uric Acid

The shift to using less oxygen leads the body to break down the DNA component adenine, which generates uric acid. At the same time, the lean tissue and overall weight loss which stems from higher altitude also generates more uric acid while it is happening (although being obese also causes higher uric acid levels). Those who remember my earlier post in which I was diagnosed with gout, may be interested to know that the gout was probably borderline until I moved to Cuenca. Uric acid at moderate levels is an antioxidant; it is only in people predisposed to higher levels that the uric acid becomes toxic and leads to gout, and also can raise blood pressure, increase the risk of heart attack, and damage the kidneys. My last blood test measurement of uric acid was VERY high.

Telomere length

Telomeres are a part of your DNA. They are shortened every time a cell replaces itself, so telomere length is considered a good indicator of future natural lifespan. Telomeres are longer when living at higher altitude for a long time.

Interaction among heart, lungs, and liver

The interaction among heart, lungs, liver, and kidneys at altitude is very complex.

To begin with, the decrease in breathed oxygen at high or moderate altitude triggers a reflex in the lungs; the blood vessels in the outside portion of the lungs shut down, so that more blood goes to the center part of the lungs where more air is coming from the outside world. This effect is increased even more in people who smoke or are obese. This increases the amount of oxygen the lungs can deliver to each drop of blood. This reflex occurring too fast is the cause of HAPE, mentioned above, within the first few days of reaching altitude.

Pulmonary Circulation is affected by living at altitude

However, the overall decrease in blood passing through the lungs over months causes a back-pressure in the pulmonary artery (see diagram) which carries blood from the right side of the heart to the lungs. This can cause the tricuspid valve, on the right side of the heart, to be unable to close completely, a condition called tricuspid insufficiency (my echocardiogram showed slight tricuspid insufficiency and borderline elevated pulmonary arterial pressure). When this happens, blood tends to back up into the liver, causing damage to the cells of this organ and causing mildly elevated liver enzymes.

Stress on the Kidneys

The kidneys use a great deal of oxygen to filter and concentrate the toxins in the blood so they can be passed out in the urine. This makes them very sensitive to a decrease in available oxygen. At the same time, remember that the body is eliminating fluid by generating extra urine as mentioned above.  It is very common for the indicators of kidney health, such as creatinine levels and blood levels of urea (BUN) to increase when the body is coping with high-altitude stress. If the uric acid levels are also high, this puts even more stress on the kidneys.

Impaired Thinking, Perceptual Changes, and Depression

Living at altitude appears to result in impaired hand-eye coordination and rapid decision-making and balance problems, as well as verbal learning and memory, but not verbal fluency. Blue-yellow color vision is impaired and so is color vision in general. Depression and suicide appear to be stimulated, and responses to psychiatric medications altered.

Overall Mortality

Statistically, people who live at high altitude are at lower risk of dying of strokes and heart attacks. However, they are at greater risk of dying from chronic obstructive pulmonary disease, suicide, and pneumonia. Some cancers are more common at altitude and others are less common. The all-cause mortality rate in the United States, at least, is lower for people at higher altitudes. However, there are a lot of differences in lifestyle and ethnic composition between people who live at high altitudes and people who live at sea level, so no firm conclusions can be drawn.

Take-Home Messages

I hope that this blog post will help anyone who is thinking of relocating from sea level to a higher altitude. Remember, chronic mountain sickness or mal de montaña occurs in only a small percentage, maybe 1-3%, of people who decide to live at high altitude. Don’t imagine, as I did, that moving to altitude is like exercise, and assume that after you adapt to it you will be just fine. The altitude does place ongoing stress on your body.  Most healthy people can adapt to this stress and, in fact, thrive.
A few things that should give you pause about moving to high altitude are: pre-existing pulmonary hypertension or COPD. Pre-existing high blood pressure. Pre-existing kidney disease. Having a family member with altitude sickness. All of these are major red flags, and if you ask your medical specialist about them, they will probably advise you not to go.

Some things that raise your chances of failing to acclimate: Obesity; family or personal history of gout; smoking tobacco; heavy drinking. Keep in mind that I met many obese people and many heavy smokers and heavy drinkers who nonetheless had lived years or decades in Cuenca with no obvious signs of mountain sickness.

However, some people who are apparently quite healthy and have none of these risk factors will nonetheless develop health problems at altitude which would not affect them at lower elevations. These longer-term problems may be something you can live with for a while, maybe months or years. But perhaps they are something you don’t want to live with. Perhaps they are something that will increase with time until it becomes urgent that you leave. I am keeping this in mind and exploring the possibilities for a leisurely relocation to a lower altitude sometime in the next year.

Although I am disappointed, I don’t regret for a moment moving to Cuenca. This city is a jewel and my time here is turning out to be a joy despite the burden of health issues. I encourage anyone thinking about it to give it a try. But, be aware that you may not be able to tolerate the altitude in the long term. Have a back-up plan.

And wherever you are, enjoy every moment!

Afterword: This post has proved very popular as expats and would-be expats investigate the potential effects of living at altitude on their blood pressure, liver, and kidneys, and causing depression. I am updating this in January, 2017, and I have moved back to the USA after being scared away from the coast of Ecuador by the big earthquake in April, 2016. The only thing I am sorry about is that I shipped all my belongings to Ecuador and then had to ship them back, which proved very expensive. Cuenca is a beautiful city and not a day goes by that I don’t miss it. Even facing the uncertainty of possible altitude sickness, I still recommend that you take the chance to experience this jewel of the Andes!