The power of exercise: buffering the effect of chronic stress on telomere length

Abstract

Background: Chronic psychological stress is associated with detrimental effects on physical health, and may operate in part through accelerated cell aging, as indexed by shorter telomeres at the ends of chromosomes. However, not all people under stress have distinctly short telomeres, and we examined whether exercise can serve a stress-buffering function. We predicted that chronic stress would be related to short telomere length (TL) in sedentary individuals, whereas in those who exercise, stress would not have measurable effects on telomere shortening.

Methodology and principal findings: 63 healthy post-menopausal women underwent a fasting morning blood draw for whole blood TL analysis by a quantitative polymerase chain reaction method. Participants completed the Perceived Stress Scale (Cohen et al., 1983), and for three successive days reported daily minutes of vigorous activity. Participants were categorized into two groups-sedentary and active (those getting Centers for Disease Control-recommended daily amount of activity). The likelihood of having short versus long telomeres was calculated as a function of stress and exercise group, covarying age, BMI and education. Logistic regression analyses revealed a significant moderating effect of exercise. As predicted, among non-exercisers a one unit increase in the Perceived Stress Scale was related to a 15-fold increase in the odds of having short telomeres (p<.05), whereas in exercisers, perceived stress appears to be unrelated to TL (B = -.59, SE = .78, p = .45).

Discussion: Vigorous physical activity appears to protect those experiencing high stress by buffering its relationship with TL. We propose pathways through which physical activity acts to buffer stress effects.

Figure 1. Fitted Probability of short telomeres as a function of perceived stress for sedentary and active individuals.

Note. Physical activity categories are based on whether the participant met CDC recommended levels of exercise per week. Perceived stress ratings are based on the Perceived Stress Scale. The interaction effect was significant (p<.05), indicating that the relationship between perceived stress and telomere length was significant in inactive participants only. The Y axis probability presents the probability of categorization into short telomere length (bottom tertile) as a function of perceived stress in inactive (top of figure) versus active (bottom of figure) participants. Probability scores were calculated from the fitted regression equations, assuming mean BMI and education level.

Figure 2. Relationship between perceived stress and telomere length as a function of physical activity.

Note. Physical activity categories are based on whether the participant met CDC recommended levels of exercise per week. Perceived stress ratings are based on the Perceived Stress Scale. The relationship between perceived stress and telomere length was significant in sedentary participants only.