SMOKING AND MALE REPRODUCTION - A REVIEW

Because of the large number of men worldwide who smoke and the fact th at cigarette smoke contains known mutagens and carcinogens, there has been concern that smoking may have adverse effects on male reproductio n. A review of the epidemiological literature indicates that cigarette smoking is associated with modest reductions in semen quality includi ng sperm concentration, motility and morphology. The associations betw een male smoking and sperm concentration and motility are stronger amo ng studies of 'healthy' men (e.g. volunteers and sperm donors) than am ong men fi-om infertility clinic populations. Smoking has also been as sociated with alterations in hormone levels in males, for example incr eases in the levels of oestrone and oestradiol. Despite modest reducti ons in semen quality and altered hormone levels among smokers compared to non-smokers, studies have not shown a reduction in male fertility in association with paternal smoking. There is some evidence to sugges t that paternal smoking is associated with congenital anomalies and ch ildhood cancer (with ORs in positive studies generally < 2.0). Smoking has not been shown to be mutagenic to human spermatozoa, although stu dies have been small and have had methodological shortcomings. It is c oncluded that, although smokers as a group may not experience reduced fertility men with marginal semen quality who wish to have children ma y benefit from quitting smoking, since several small studies indicate the potential for improved semen quality after quitting smoking. More research on the benefits of quitting smoking among men with marginal s emen quality is needed. Methodological improvements in studies aimed a t clarifying the association between paternal smoking and reproductive and developmental outcomes in offspring should include obtaining accu rate paternal smoking dose information, evaluating smoking exposure in formation in relation to various time windows (e.g. prior to conceptio n, during gestation), and controlling for potential confounders and mo difying factors such as age and maternal smoking habits. More sensitiv e and specific laboratory assays and increased sample sizes are requir ed to establish whether smoking induces mutations in human spermatozoa .