[Impact of cigarette smoking on human sperm DNA integrity]

To investigate the influence of cigarette smoking on human sperm DNA integrity.

Totally, 784 cases of male infertility were selected from our case database and grouped according to whether they were smokers or nonsmokers, how much they smoked (< or = 10, 11-19 and > or = 20 cigarettes/d) and how long they smoked (< or = 5, 6-9 and > or = 10 yr). Sperm DNA integrity was measured using sperm chromatin structure assay (SCSA) and flow cytometry. DNA fragmentation and immature spermatozoa were expressed by the DNA fragmentation index (DFI) and high DNA stainability (HDS) respectively. Conventional sperm parameters and sperm DNA integrity were compared among different groups.

The total semen volume and percentage of grade a + b sperm were lower and the sperm morphological abnormality was higher in the > or = 20 cigarettes/d and > or = 10 yr groups than in the others (P < 0.05). DFI and HDS were significantly higher in the smokers than in the nonsmokers (P < 0.05). HDS was negatively correlated with the percentage of grade a + b sperm (r = -0.18, P < 0.05) and both DFI and HDS were positively correlated with the rate of sperm malformation (r = 0.31 and r = 0.39, P < 0.05).

Smoking more than 20 cigarettes a day or longer than 10 years has deleterious effects on the semen volume, percentage of grade a + b sperm and sperm morphology of the smokers. Cigarette smoking decreases sperm DNA integrity and nuclear maturation.