Effects of cigarette smoking on semen characteristics of a population in Mexico.

A study of semen quality was conducted in 197 smoking and 161 non-smoking men undergoing initial infertility investigation. The men were allocated into groups according the number of cigarettes smoked per day < 10 (n = 57), 11-20 (n = 115), and > 20 cigarettes (n = 25). Smokers had significantly poorer sperm density (P < .005), a lower percentage of viability (P < .007), a lower percentage of normal sperm morphology (P < .005), and the percentage of motile sperm was lower (P < .005). These parameters were worse in the heavy smoking groups. Thus the present study corroborates reports of detrimental effects of cigarette smoking on sperm characteristics. Further studies are needed to explain the mechanism by which smoking affects spermatogenesis.