Thursday, May 27, 2010

Exercise and Fitness Buffer the Life-Shortening Effects of Psychological Stress

A new article published in the on-line Public Library of Science journal reports on a study which compared the effects of chronic psychological stress on either sedentary or physically active people.

The study involved looking at telomere length in 63 healthy post-menopausal women. The researchers measured telomere length in the women, then had the women complete the Perceived Stress Scale. After this, for three days the women reported their daily investment of time (in minutes) in vigorous physical activity. The researchers then calculated the likelihood of having long or short telomeres relative to age, body mass index, education, perceived stress, and activity level.

Among the sedentary women, each unit of increase in perceived stress (on the Perceived Stress Scale) was associated with a 15-fold greater odds of having short telomeres, a marker of biological aging. However, among those who got an average of at least 14 minutes daily of vigorous exercise, the researchers found no increase in odds of short telomeres regardless of perceived stress.

In other words, it appears that people who engage in sufficient, but not excessive, physical activity have greater resistance to the aging effects of psychological stress.

The authors propose several explanations for the beneficial effects of activity:

1. Moderate physical activity appears to increase endogenous antioxidant production, which may buffer the pro-oxidative effects of stress.
2. Physical fitness and activity appear to blunt neuroendocrine responses to stress, particularly reducing sympathetic nervous system responses and cortisol production.
3. Physical activity appears to reduce cognitive rumination (i.e. it quiets the mind), which results in less sympathetic nervous system activity and lower cortisol production under stress.

In short, this study suggests that by engaging in regular physical activity we protect ourselves from both the immediate and the aging effects of stress. We would expect this from a species that evolved by route of a lifestyle that required physical activity in the pursuit of food. Proper exercise is essential to not only physical but also mental health.