The Stress Test
An Interview with
Dr. Steven M. Horvath
Director of the Institute of Environmental Stress
by Colin Campbell
Photography by Jurgen Hilmer
Since 1965, the Institute of Environmental Stress has chilled, poked, baked, gassed, dunked, and spooked 12,928 men, women, and children at UC Santa Barbara. Dr. Steven M. Horvath, professor of biomedical engineering and physiology and the director of the institute, is in charge. "We're studying how normal people react to different kinds of stress," he explains, "and what happens to their ability to adapt to stress as they grow older."
For a man whose subject is stress, Dr. Horvath, age 71, seems remarkably calm. He often dresses in sandals, lightweight pants, and a crisp white sports shirt-a familiar sight on the fifth and sixth floors of UCSB's biological sciences building. The doctor takes leisurely puffs on his pipe as he moves through the halls, and when he joins his colleagues in a treadmill room, high altitude chamber, or any of the other laboratories that make up the institute, his clear blue eyes convey a mixture of interest, compassion, and amusement.
Dr. Horvath began studying stress at Ohio State University in 1939. He went on to Harvard, and later worked at the famous Harvard Fatigue Laboratory. During World War II, when the facility was divided among the military services, Dr. Horvath was sent to the U.S. Army medical research lab at Fort Knox, Kentucky. From there he went to the South Pacific, to the Arctic, to the tops of mountains, testing and studying the ability of normal young men to survive and adapt to stressful situations.
Dr. Horvath came to UCSB in 1962, and by 1965 the Environmental Stress Institute was in operation, chartered to study the adaptive potential of people of all ages. Today, rivaled only by the U.S. Armored Medical Research Lab in Natick, Massachusetts, the institute has 26 researchers in bioengineering, physiology, and cardiorespiratory diseases.
"The institute is extraordinary," Dr. Horvath says proudly, "as I think everyone who comes here can see. We have visiting researchers from all over--Australia, China, Japan, Europe, Canada, Mexico--and they all consider this one of the most extraordinary laboratories in the world."
Right: After subjecting 12,928 volunteers to stress since 1965, Dr. Steven M.Horvath believes the institute is gaining insight into how people age. "We probably won't add years to life, " he says, "but we may add life to years."
COLIN CAMPBELL: A popular notion is that stress is bad. Yet you've stated previously that "exposure to stress may be essential to human development and well-being."
STEVEN HORVATH: I still think so. If you take an individual and remove all stress from him, that individual has a greater propensity to get into difficulty. For instance, exercise is a stress. What happens if you don't exercise? You fall apart. How much exercise is not enough and how much is too much? It's hard to say. We've found people who do just fine with a certain amount of walking. Many of our older subjects have never done any exercise except to walk, and some of them are in much better condition than younger individuals.
In the beginning we did studies where we isolated stresses, and they convinced us early in the game that a certain amount is essential for survival. I feel very strongly that if you have no stress, you're in trouble. If you have excess stress, you're also in trouble. But you can't survive without stress.
The Author Under Stress
On a Tuesday morning last summer, I reported to the Pulmonary Function Lab at the Environmental Stress Institute and had 15 electrodes glued to my neck, chest, and back. I climbed onto an exercycle.
The electrodes led to a computer. For three minutes the computer monitored my resting heart rate (75 beats per minute) and respiration; then I pedaled the cycle at 60 revolutions per minute against resistances of 300, 450, 600, and 750 kilograms, for three minutes each. As the resistance went up, so did my heart rate, peaking at 160. 1 was still breathing normally.
This was a calibration test. And this fall I will do it again with other stresses added-probably a percentage of air pollution-to see how my performance declines under the additional stress.
The test measured 30 parameters, including systolic time intervals, systolic time ejection, cardiac output (volume of blood my heart pumped), flow velocity, and heart pressure waves.
Five years ago this kind of test could have been done only by catheterization: inserting a probe into the big vein in the thigh and sliding the probe along the blood vessels into the heart itself. And then only the resting heart functions could be measured-not many people want to ride a bike with a catheter in the heart. "Our noninvasive methods are five to ten years ahead of the rest of the world," Dr. Horvath told me.
After I finished pedaling, there was a three-minute recovery period. "This test would cost you $1640," he said, and the graph readout suddenly spiked. "But you I ve found out that your heart is in very good shape for a man of your age."
- Colin Campbell
CAMPBELL: Who are these people you're studying?
HORVATH: Well, they're different groups of volunteers. We've studied people aged seven to ten, for instance, and many groups from the university population--ages 19 to 25. We have people from Santa Barbara up to age 80, and then there are a few people from all over the country who have been part of continuing programs for a long time. Our oldest subject is a man 93; he's been studied now for 35 years. He comes back every couple or three years....
One trouble is that you generally tend to look at an individual from the standpoint of the number of years he's lived. What you really need to know is the physiological age. I'll use the 93-year-old man as an example. He behaves and responds and adapts to environmental stress with the ability of a 60-year-old. We also have 60-year-olds whose responses are typical of individuals who are very much older. How much older? We don't know, and the reason is we don't have a continuum. And until we get a continuing set of measurements on enough people so we can predict what's going to happen at a given physiological age, we just have our hands tied.
You need to look at an individual over the entire length of his life. Now, how can you do this? You can't do it under the way the system works now, because you never know if you're going to be funded next year or five years from now. So you have to have some sort of a center, like our Center for Aging, where you can keep this kind of data. The institute now has a data base of information on 12,928 individuals. That's a start.
CAMPBELL: Is it important that you have the same individual? Couldn't you just study 8-year-olds, 10-year-olds, 25year-olds? HORVATH: Oh, no. Look at someone who's 75 today. Now look at someone who's 10. Would he be, at 75, in the equivalent situation? You have to wait 65 years to find out!
And I think you can predict that they won't be the same. The environment has changed. The person who is now 82 was born in 1900. The stresses on his early life were very different from the stresses imposed on an individual born today, who will be 82 in the year 2064. And the kinds of stress he faces as he grows are going to be extraordinarily different from today's 82-year-old, not to mention our own. We won't know what to expect until we get an even bigger sample and look at the results long enough.
CAMPBELL: What kinds of stress are you looking at?
HORVATH: At first we decided that one of the basic stresses would be exercise--ordinary stress on the body--because it brings into play every physiological system. Then we added heat. How would subjects react when they were exposed to a hot environment?
One of the studies I was doing at the Harvard Fatigue Laboratory was with a number of young soldiers. We studied their ability to adapt to a hot environment like that of North Africa. While we were looking at the soldiers, we also tested ourselves. Thirty years after the test, the average age of the scientists was 65 to 70, and the soldiers had gone from 20 to 50. We were able to locate all but one.
In 1971 we got everybody back together and put them through exactly the same protocol and the same tests we gave them in 1941. The interesting thing we found was that everyone could adapt to the heat. It took longer, but they could adapt. For instance, in 1941 it took one scientist in his 40s seven days to adapt. And when we retested him, it took him 21 days. We feel that this slower rate of adaption may account for the number of older people who die during heat waves.
We've recently been looking at how three groups--one in their 20s, one in their 40s, and one in their 70s--are able to handle the other extreme--cold environments. We know that lately, more old people are not surviving the cold winters. And we feel this study may be important because of our diminishing energy sources.
We found that older individuals in general have a different mechanism by which they respond to the cold. They don't raise their metabolism, don't shiver as much to increase their heat production. Instead, they let their body temperature fall. And there's a difference between how older men and women respond, too, although we haven't fully analyzed it yet.
CAMPBELL: Does one group seem to adapt better?
HORVATH: Yes, one seems to be better.
CAMPBELL: Which one?
HORVATH: [Laughs] I'm not going to say yet. We measured about 200 different factors on these people, and right now most of that data is in the computer. We have an impression, but we're not sure the impression is valid. But you stop and think about it. Women on the average live a lot longer than men do. Women who get to be 65 have an average life expectancy of another 18 or 19 years; men who get to be 65 have an average expectancy of between 5 and 7 more years, maybe up to 10.
Another interesting thing we do up here has to do with hormones. The production of estrogen in women goes down as they age, and their level of testosterone, the male hormone, goes up. In the male? It's the opposite.
The significance of this escapes us at the moment. But it does indicate that certain things are occurring that might allow some people to live longer than others--some sort of interesting metabolic response-, but of course there are many other factors.
CAMPBELL: Aren't there also hormones directly involved with stress?
HORVATH: Oh, yes. Mainly hormones from the adrenal glands and from the sympathetic nervous system. They're part of the old fight or flight phenomena reported by Walter P. Cannon of Harvard back in the 1920s. These substances--cortisols, catecholamines, corticoids--result from certain levels of stress.
But now we're discovering other hormones and thousands of other hormonelike substances. We have very exotic methods to measure extraordinarily small quantities of hormones in the bloodstream. We measure in picograms-billionths of a gram. There are hormones that we once thought affected only the gastro-intestinal track, but now have been shown to affect the brain. Most people in the past, unfortunately, have examined these in the urine. They put somebody in a stressful situation, and then they test the urine. They find the epinephrine levels are up. But that doesn't tell you everything. It only tells you what goes through the kidneys. It doesn't tell you what has gone through the body, what has been destroyed or used up. Now we have techniques that enable us to measure substances in the bloodstream as they're being used.
We're also finding many other substances that have effects in minute quantities on the central nervous system, which then affects the rest of the body. We used to think only one hormone was involved, acetylcholine. Now we talk about serotonin, norepinephrine, dopamine. And there are protein substances--small molecules that are still so new they don't have names yet. We're beginning to see that even the simple amino acids that we consider necessary for our survival are effective not only because of their nutritional value, but also because of their involvement in hormonal production.
CAMPBELL: Of these more recently discovered substances, do some seem more involved with stress than others?
HORVATH: Well, the catecholamines, epinephrine, norepinephrine seem to be the most responsive of all. When you get the norepinephrine going in the bloodstream, it causes the heart to beat faster, causes you to feel like you're pounding away. You breathe faster, your muscles get tense. They're all related, all these events caused by stress.
Right: A long-distance runner prepares for a multiple stress test in one of the treadmill rooms. T he institute is gathering data on men, women, and children of all ages, under all kinds of conditions.
CAMPBELL: You've mentioned exercise and heat as two types of stress you've studied. Are there more?
HORVATH: Oh, yes indeed. Our basic philosophy is that you can't tell a great deal about how people respond to stress unless you look at how they react to a series of stresses. Most people in the real world have many stresses affecting them. So we're subjecting volunteers to multiple stresses in different situations.
We do things like comparing two people, who know each other fairly well, while they're exercising. One of them might be in excellent condition and the other might not be in such good shape. By the use of varying devices, we make the one in excellent condition look bad and the one in not-so-good shape look good. That causes considerable stress--competitive stress. And that affects the body.
We also use noise. That's the new one we've added. We found that noise does more than just induce psychological stress. It induces an effect on the heart, which can be seen on an electrocardiogram. Studies on animals have indicated
that hypertension can develop as a result of noise, although we haven't used levels high enough to see evidence of this on human subjects.
Our altitude tests are a good example of applying multiple stresses to people in different situations. In a five day test, we have sleeping volunteers connected by electrodes to instruments that record and monitor their responses. When the instruments report that the subjects have reached an episode of deepest sleep--the lowest metabolic point--we wake them up, ask them to pedal an exercycle, and give them psychological tests under varying levels of air pressure, air pollutants, oxygen, and temperature.
When we first take the young males up to a simulated 14,000 feet in the altitude chamber, we usually have to bring half of them back down because of breathing difficulties. Compared to the number of young men who get into trouble, older men show very little effect of mountain sickness in the first couple of days. So far most of our altitude studies have been with males. But recently we tested a series of young women and found some startling differences in their response. The young women show virtually no ill effects, very similar to the older men.
We've started to develop some broad concepts of what happens to people as they get older, in relationship to what kind of physical and psychological stresses they face.
CAMPBELL: Can you give an example of a psychological stress?
HoRvATH: Well, attainment of vigilance is a stress. Suppose you're driving a car on the Los Angeles freeways. You've got to be vigilant. We call that the basis of stress. There's an arousal that raises your heart rate and increases respiration, related to the endocrine glands and the sympathetic nervous system. Some people sense it, some people don't. But the stress is there.
Now, one of the things that cars produce is carbon monoxide. What happens to people when they have to maintain vigilance in their cars? Well, carbon monoxide does the same thing, theoretically, as high altitude. It's called hypoxia.
Let's say you went up to high altitude and I asked you to do a very simple task, say, write your name. If you were writing your name here, at sea level, you'd write the way you usually do. After a certain altitude, you still think you're writing it okay, but if somebody else looks at it, it's almost indecipherable. This is because of hypoxia.
We've found that air pollution can cause a similar effect. That's one of our major research areas today. The hemoglobin in your blood mistakes carbon monoxide for oxygen. It likes carbon monoxide much better than oxygen, and won't let go of it. So the more smog you breathe, the more you diminish your potential for using oxygen
When you're driving in heavy traffic with your windows open, you can get a fairly high level of this carboxyhemoglobin in your blood and lose the ability to maintain vigilance. You're still worried about traffic and how to handle it, but you may make errors that you're unaware of, just as the subjects in the altitude chamber were unaware they were writing their names wrong.
CAMPBELL: What do you see as the future of the institute?
HORVATH: Our major goal is to be able to look at people over a long period of time. And we're especially interested in the problems of aging. That's why we're setting up the Center for Aging this year. We hope to stimulate interest in some longterm programs.
Santa Barbara is an ideal place to study this. We have many retired people here--24 percent are over the age of 60. These people are in an environment that is probably the most equitable in the country. We can learn about their potential here.
One of the greatest problems facing the human race is the increased number of people surviving to their 70s, 80s, 90s. It's not simply that they are living longer. It's the fact that these older people are going to have to be productive long after the usual retirement age because there are fewer younger people coming along to support them.
The medical profession is reducing the number of people dying of heart disease and cancer, increasing life expectancy. Now, why should we have people who can potentially live 10 or 15 years longer--what's the point unless they feel it is worthwhile, unless they can do something worthwhile?
Right now we are just not using the capability of our older people. First, we've got to find out what those capabilities are. Second, we have to find ways to improve them. I don't think improvement will come from a new sex hormone or from drugs. I think it will be based on our understanding of what is going on in the individual as he ages.
What we've got to do, the biggest challenge to the institute, is to add life to years, rather than years to life. I don't think we'll add a single second to the life of an individual. What we have to work on is making life worthwhile for people, make them not only enjoy it, but more importantly, make them productive. That's the future. |
