1. Reduced time spent sitting by elderly individuals was significantly associated with telomere lengthening in blood cells.
2. Increases in time spent exercising was associated with a decrease in telomere length, but not significantly.
Evidence Rating Level: 2 (Good)
Study Rundown: Telomeres are repeating nucleotide sequences at the end of chromosomes that serve to prevent chromosome deterioration in subsequent cell generations. Evidence suggests longer telomere length is associated with longevity and improved physical health, while shorter telomere lengths have been associated with factors such as smoking and depression. Limited evidence is available regarding the relationship between physical activity levels and telomere length. In this secondary sub-analysis of data from a randomized controlled trial studying the effects of physical activity on prescription (PAP) on cardiometabolic risk factors, it was found that reduced sitting time was associated with an increase in telomere length. Additionally, increased amount of time spent exercising was associated with shortening of telomere length, but not significantly. These data suggest that physical activity is associated with changes at the molecular level. Given the known association of telomere lengthening with positive health outcomes, these results may provide evidence to support avoidance of sedentary behaviors.
A strength of this study is that the physical activity intervention from the original trial resulted in significant positive changes in exercise measures. The limited sample size presents a notable limitation, and the generalizability of results should be considered with caution. Further, in the original trial physical activity levels were measured via self-reported questionnaire, which often result in overestimation of physical activity levels. Nevertheless, these data should spur subsequent investigations to both replicate and advance these findings.
In-Depth [secondary analysis of a randomized controlled trial]: This study evaluated the association between changes in physical activity and changes in telomere length. In 49 randomly selected older individuals who originally participated in a randomized control trial of a physical activity intervention, changes in steps taken per day, time of moderate- and low-intensity exercise, and time spent sitting were correlated with change in telomere length from baseline to 6-month follow-up. The relationship between changes in physical activity measures and changes in telomere length was evaluated with Spearman rank correlation. Within-group and between-group differences were analyzed using paired t-tests and analysis of covariance, respectively. In this sub-analysis, it was found that telomere lengthening was significantly correlated with reduced sitting time (rho=-0.68, p=0.02) in individuals randomized to the physical activity intervention. Increases in exercise time were negatively associated with changes in telomere length in both the control and intervention groups, although the correlations were not statistically significant. No relationship was found between changes in steps per day and changes in telomere length.
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