Telomeres are repetitive DNA-protein complexes that protect the ends of linear chromosomes and maintain genomic stability. They undergo erosion with each cycle of cell division, and oxidative stress and inflammation accelerate this shortening. Critically short telomeres may lead to several processes implicated in carcinogenesis, including chromosomal degradation, end-to-end fusion, and atypical recombination. Telomere length in peripheral blood leukocytes (PBLs) is a potential indicator of cellular aging and shortened leukocyte telomere length (LTL) has been linked to an increased risk of various cancer types, such as bladder, lung, and renal-cell. Regular physical activity reduces the risk of developing many cancers, and studies have observed lower levels of oxidative stress and inflammation in regularly active individuals. However, few population-based studies have examined the relation between physical activity and LTL, and none has addressed sedentary behavior. In addition, information is scarce on the role of exercise intensity and type in this relation. The authors therefore examined cross-sectionally the association between physical activity, sedentary behavior, and LTL among 7,813 women ages 43–70 in the Nurses' Health Study. Participants self-reported activity by questionnaire in 1988 and 1992, and sedentary behavior in 1992. Telomere length in PBLs, collected in 1989–1990, was measured by quantitative polymerase chain reaction. Least squares mean telomere length (z-score) was calculated after adjustment for age and other potential confounders. Total activity was positively associated with LTL. Compared with the least active women, those moderately or highly active had a 0.07 standard deviation (SD) increase in LTL (p-trend=0.02), a difference corresponding on average to 4.4 years of aging. Greater moderate-or vigorous-intensity activity was also associated with increased LTL; women who exercised 2–4 hours per week, an amount corresponding to current US guidelines, had the longest telomeres (0.11 SD increase for 2–4 vs. <1 hours/week; 0.04 SD increase for 7+ vs. <1 hours/week; p-trend=0.02). Among the individual activities, greater calisthenics or aerobics was associated with longer telomeres (0.10 SD increase for >2.5 vs. 0 hours/week; p-trend=0.04). Associations remained after additionally adjusting for body mass index. Time spent on other activities and time spent sitting were unassociated with LTL. Although associations were modest, these findings suggest that even moderate amounts of activity may be associated with longer telomeres, providing insight into the understanding of how exercise may influence cancer risk on the cellular level. These findings warrant further investigation in large prospective studies.

Citation Information: Cancer Prev Res 2011;4(10 Suppl):B112.