Effect of age and sex on the level of DNA strand breaks and oxidatively damaged DNA in human blood cells.

DNA damage measured by the comet assay is a well-established biomarker in studies on environmental and occupational exposures, dietary factors and clinical outcomes. Age and sex are typically regarded as confounding factors that are controlled by either selective inclusion criteria of subjects or adjustment in the statistical analysis. This review assesses the influence of age and sex on levels of DNA damage in leukocytes in study populations of healthy subjects. Analysis of unadjusted results in the studies indicates that the level of DNA strand breaks increases by 1% per year (95% CI: 0.9%-1.1%, linear regression analysis weighted for the number of subjects in the individual studies). The studies also show a slightly higher level of DNA strand breaks in men than women (8%, 95% CI: 0.4%-17%) in unadjusted analyses, which is not robust in studies with adjusted analyses. The attenuation of effect in adjusted analyses of DNA strand breaks in leukocytes indicates that the effect of age and sex may be driven by differences in lifestyle factors or other exposures. There do not appear to be differences related to age and sex on basal levels of oxidatively damaged DNA in leukocytes. In summary, the results indicate influences of both age and sex on DNA damage in the comet assay, which may be mediated by lifestyle factors or external exposures rather than direct effects of age and sex.