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Aim: To examine whether reproductive hormones play a role in the association between body mass index (BMI) and semen quality. Methods: Semen quality and testosterone (T), luteinizing hormone (LH), follicle-stimulating hormone (FSH) and estradiol (E2) were evaluated in 990 fertile males with age 38.9 ± 9.7 (mean ± SD) years recruited from the Chinese general population in 2001 and 2002. Results: Semen quality was reduced among underweight (BMI < 18.5) compared with normal (BMI 18.5–24.9) and overweight (BMI 25.0–29.9), but the associations were independent of reproductive hormones. After adjustment for the potential confounders, underweight men had reductions in sperm concentration (22.4 × 10 6 /mL), total sperm count (52.9 × 10 6 ) and percentage of normal sperm forms (6.9%) compared with men with normal BMI. Being underweight may be a risk factor for low sperm concentration (OR: 4.68, 95% confidence intervals [CI]: 2.01–10.91). Otherwise, being overweight may be a protected factor for low sperm concentration (OR: 0.25; 95% CI: 0.08–0.83) and low total sperm count (OR: 0.37, 95% CI: 0.15–0.87). Conclusion: Low BMI was associated with reduced semen quality. The associations between BMI and semen quality were found statistically significant even after adjustment for reproductive hormones. Reproductive hormones cannot explain the association between BMI and semen quality. (Asian J Androl 2007 Nov; 9: 827–834)

Aim: To investigate the relationship between Ureaplasma urealyticum (UU) infection and semen quality. Methods: From 2001 to 2003, 346 eligible patients aged 20–45 years were invited from two hospitals in Shanghai, China, to participate in an investigation which included questionnaires about general and reproductive health, an external genital tract examination, UU culture and semen analysis. Multiple linear regression models were used to examine whether UU had a significant effect on semen quality after adjustment for confounding factors. Results: Findings suggested that UU infection was associated with higher semen viscosity and lower semen pH value. Sperm concentration was lower in UU positive subjects than that in UU negative subjects (54.04 × 10 6 /mL vs.70.58 × 10 6 /mL). However, UU did not significantly affect other semen quality indexes. Conclusion: UU infection of the male genital tract could negatively influence semen quality. (Asian J Androl 2006 Sep; 8: 562–568)

Aim: To assess whether exposure to computers harms the semen quality of healthy young men. Methods: A total of 178 subjects were recruited from two maternity and children healthcare centers in Shanghai, 91 with a history of exposure to computers (i.e., exposure for 20 h or more per week in the last 2 years) and 87 persons to act as control (no or little exposure to computers). Data on the history of exposure to computers and other characteristics were obtained by means of a structured questionnaire interview. Semen samples were collected by masturbation in the place where the semen samples were analyzed. Results: No differences in the distribution of the semen parameters (semen volume, sperm density, percentage of progressive sperm, sperm viability and percentage of normal form sperm) were found between the exposed group and the control group. Exposure to computers was not found to be a risk factor for inferior semen quality after adjusting for potential confounders, including abstinence days, testicle size, occupation, history of exposure to toxic substances. Conclusion: The present study did not find that healthy men exposed to computers had inferior semen quality. (Asian J Androl 2005 Sep; 7: 263–266)