Mediation By Physical Activity On Relationship Between Stress And DNA Damage In Puerto Rican Adults

Oxidative damage to deoxyribonucleic acid (DNA) is associated with risk of chronic diseases like cardiovascular disease. Chronic stress has been previously associated with increased oxidative DNA damage through the release of stress hormones and inflammation. Physical activity is a modifiable factor that has been associated with both lower stress and lower oxidative stress. Puerto Rican adults experience high levels of stress as well as disparities in chronic conditions. PURPOSE: To examine the potential mediation by physical activity on the relationship between perceived stress and oxidative DNA damage. METHODS: Data was taken from Boston Puerto Rican Health study, a prospective cohort examining biological, social, environmental and lifestyle factors associated with chronic disease in this population. Oxidative DNA damage (8-hydroxy-deoxyguanosine) was collected from urine and analyzed using enzyme-linked immunosorbent assay and adjusted for creatinine excretion. The perceived stress scale measured perceptions of stressful life events, with higher values indicating higher feelings of stress. Physical activity was measured as metabolic equivalents using from modified Paffenbarger questionnaire. Multivariable linear regression models examined associations between perceived stress and DNA damage, as well as the relationship between perceived stress and physical activity. Mediation models examined associations between perceived stress and oxidative DNA damage including physical activity as a covariate. RESULTS: Higher perceived stress was directly associated with higher oxidative DNA damage (β: 0.65 ± 0.25, P = 0.01) and inversely associated with perceived stress (β: -0.06 ± 0.01, P < 0.001). The association between perceived stress and DNA damage was still significant in the mediation model, but the effect was attenuated (β: 0.57 ± 0.25, P = 0.02). Significant mediation effects were confirmed via a Sobel test (test statistic: 1.97, P = 0.04). CONCLUSIONS: The relationship between chronic stress and oxidative DNA damage is mediated by physical activity in Puerto Rican older adults. This suggests potential protective effects of physical activity on oxidation of DNA, which may have important implications for the development of chronic conditions in this high-risk population. Supported by: NIH P01 AG023394