The impact of cigarette smoking on human semen parameters and hormones

BACKGROUND: In this prospective study, semen parameters and hormone concentrations of infertile smokers were compared with infertile non- and ex-smokers. We also determined how many men with idiopathic infertility would stop smoking in an attempt to improve their fertility. METHODS: 1104 men (517 non-smokers, 109 ex-smokers and 478 smokers) with infertility for at least 1 year were evaluated. Evaluation included medical history, physical examination, hormone analysis and two semen analyses. Prior to the second semen analysis, smokers were urged to quit smoking. RESULTS: Smokers were significantly younger (P < 0.001), had significantly more round cells in their ejaculates (P = 0.003), and the percentage of ejaculates with >1x10(6)/ml leukocytes was higher in smokers (P < 0.001). Increased free and total serum testosterone (P < 0.001) and decreased prolactin levels (P < 0.001) were found in smokers. No differences were found between non-smokers and ex-smokers. Only 23.1% of the smokers versus 46% non-smokers (P < 0.001) returned for a second semen analysis, 14 of whom reduced and 15 of whom quit smoking completely. Testosterone levels were significantly lower in those who were able to stop or reduce smoking (P < 0.001). CONCLUSIONS: Smoking does not affect conventional semen parameters, but significantly increases round cells and leukocytes. Only a few idiopathic infertile smokers were able to quit smoking.