Environmental and lifestyle factors associated with sperm DNA damage.

Semen quality in the adult male can be affected by a number of environmental and lifestyle factors. However, most studies to date have only considered how sperm concentration, motility and morphology are affected by such exposures. More recent studies, outlined in this review, have begun to examine the effect of environmental and lifestyle factors on sperm DNA integrity. Important factors appear to include: (i) Physical agents such as radiation and heat; (ii) Chemical agents such as cigarette smoke, airborne pollutants, and chemotherapeutic drugs; and (iii) Biological factors including sexually transmitted infections, increasing male age, elevated body mass index and medical conditions such as insulin dependent diabetes. A number of hypotheses have been proposed to account for how sperm DNA might be damaged by these factors. There is, however, uncertainty about the most appropriate laboratory test(s) to identify and quantify such DNA damage and no convincing evidence on possible therapeutic measures.