Imagine designing an experiment – even an idealized experiment – to test the effect of meditation on life span. Animal models are useless. Best would be to take a diverse group of people, divide them into two statistically-matched subgroups, and instruct one group to meditate and the other not to. Everything else about their lives should be kept the same. But meditation doesn’t work that way. Over any substantial period of time, meditation practice is likely to change attitudes and habits and occupations. These two groups of people will no longer be comparable.
This is just one of the pitfalls in trying to scientifically evaluate claims about meditation and life expectancy. Of course, experiments with real human subjects must respect their freedom. Realistically, all we can do is to compare a set of people who meditates with another set who do not meditate. We can select them in such a way to match their ages, their sexes, their weights, diets, exercise habits, incomes and ethnicities. But these groups will have had different life experiences, different social environments, and their attitude toward life will not be similar. People who choose meditation have a take on the world and a set of values that likely leads them to pay more attention to care for themselves and others. The culture and pratice of meditation are both conducive to that. These social determinants of longevity are quite important, and any epidemiological study of meditation must use a combination of selection and ANOVA to compensate for inevitable differences between the two groups. (ANOVA stands for Analysis of Variance, and it is a common mathematical procedure for separating and evaluating various contributing causes of one outcome.) There would be inevitable ambiguity in how to translate the question into statistical terms. For example, a person may tell you that his meditation practice led him to give up smoking. Do we compare this against a matched control who continues to smoke, or to a subject who quit smoking without practicing meditation? Do we count the benefits of improved self-care as part of the benefit of meditation, or do we factor it out as if it were an independent decision?
The study we are imagining would have to include a large number of subjects with detailed information about each individual’s health and life style. It has never been attempted, to my knowledge. The studies that have been done are far more modest, and so the evidence that we have is at best tentative and indirect.
The studies that we do have fall in three categories:
- Meditators tend to be healthier. But how much of this is because people who make a commitment to meditation are more likely to care for themselves better in other ways?
For example, in a new article (Hoge 2013) naively measures telomere length in people who meditate and people who don’t. While they find a significant difference, it’s not warranted to interpret this as an effect of the meditation, because people who meditate are likely to take care of themselves better in other ways as well.
Before/after comparisons of physiology of meditators. This is very helpful and suggestive, but we must always be careful about imputing long-term benefits from a short-term response, because there are short-term challenges (like exercise and fasting) to which the body responds in ways that slow aging in the long run.
A large but questionable scientific literature that is funded by the Transcendental Meditation establishment, which has cash to spend and a product to sell. I regard this research with the same skepticism as drug trials sponsored by the drug’s manufacturer. Walton reviewed this literature a few years ago.
The best work in the field comes out of the AME center at UCSF (Aging, Metabolism and Emotion). I was impressed with one study for its clean design and significant outcome. 30 participants in an intensive meditation retreat were compared with a matched group of 30 people on a waiting list for the same retreat. Telomerase activity was measured to be 40% higher on average in the retreatants. I have written in this column and elsewhere that I believe telomere length is not just a predictor but a cause of aging and mortality. A 40% increase in telomere activity sounds like a very significant number, but the catch is that the base telomerase in humans is very low. For the most part, telomere length is in free-fall through a lifetime, and it is not clear that 40% more telomerase is enough to help that.
From the TM literature, here is a study (Walton, 2002) that demonstrates a reduction in blood pressure from meditation. Now, it’s true that high blood pressure predicts heart attacks, but it’s not necessarily true that lowering blood pressure addresses the root cause of the problem, as I’ve argued a few weeks ago in this column. Atherosclerosis increases blood pressure and atherosclerosis increases risk of a heart attack. But decreasing blood pressure without addressing the underlying atherosclerosis may not have a benefit.
The most relevant of the studies from the Maharishi Institute looked at a group of 202 older people identified as elevated risk for heart disease. They were trained in Transcendental Meditation, and Schneider et al found a 23% reduction in all-cause mortality over 7 years. This sounds impressive, until you realize how small the sample was. The result was barely statistically significant.
Here is a study by Richard Brown of Columbia that finds health benefits from yogic breathing exercises, and extrapolates from there to speculate on life expectancy.
There’s a column in Huffington Post this week by Aditi Nerurkar that parallels some of my conclusions.
My Own Suggestions for Studies I Would Like to See
Collect vital statistics from a variety of meditation studios and Buddhis sanghas for members who have died in recent years, and compare to similar statistics from selected church groups.
Train a group of cancer patients in healing meditations focused on their particular ailment, and compare outcomes to a control group trained in a generic meditation technique.
Here’s a thought: as real-time assays for telomerase become more practical, perhaps it will be possible to measure an individual’s telomerase levels while she is meditating. In biofeedback therapy, people have learned to control a great many body functions that were previously thought to be autonomic: heart rate, temperature of a particular body part, electrical activity in a specific part of the brain. Most people can learn to do this, though they can’t tell you how. The protocol is simply to provide the person with real-time feedback about any measurable property of his body, and very often the person learns after a number of sessions to make the meter move in the desired direction.
Maybe we could learn to express telomerase. Maybe there are other markers of the rate of aging that we could learn to modulate if only they were measured so that we could be offered real-time feedback.
The Bottom Line
I think there probably is a benefit from meditation for health and longevity, but it is difficult to substantiate this from the available studies. All the evidence is indirect. Perhaps the best justification for my position is that meditation has been found to increase positive affect, and people who are happier live a lot longer (“the nun study”). There seems to be a connection between chronic stress and aging, but it’s not about the objective pressures a person is under, but rather the attitude and the way in which the challenges of life are perceived. This is a central theme in the work of Elissa Epel, who first discovered the stress/telomere connection.
Studies that come out of Maharishi University are not of high quality, and aside from these there is a regrettable lack of attention to a practice for which there is preliminary evidence of broad psychological and physiological benefits and no down side.
For many of us, it is difficult to muster the consistent determination to focus our minds for a practice that we know will make our lives better. Maybe it will help to have the additional motivation that it will also make our lives longer.
This article originally appeared in Josh’s blog here: http://joshmitteldorf.scienceblog.com/2013/08/13/meditation-and-longevity/