Association between central obesity and semen quality: A cross-sectional study in 4513 Chinese sperm donation volunteers

BackgroundGeneral obesity classified by body mass index has been linked to a reduction in semen quality; however, evidence on the adverse effect of central obesity on semen quality remains limited. ObjectivesTo investigate the association between central obesity and semen quality. Materials and methodsWe conducted a cross-sectional study of 4513 sperm donation volunteers in Guangdong Provincial Human Sperm Bank during 2018-2021. Three central obesity indicators, including waist circumference, waist-to-hip ratio, and waist-to-height ratio, were measured using a multi-frequency bioelectrical impedance analysis for each subject. Semen analysis was conducted according to the World Health Organization laboratory manual for the examination and processing of human semen 5th edition. Linear regression models and unconditional logistic regression models were used to quantify the association between central obesity and semen parameters. ResultsWith adjustment for age, race, education level, marital status, fertility status, occupation, year of semen collection, abstinence period, ambient temperature, and relative humidity, central obesity defined as waist circumference >= 90 cm, waist-to-hip ratio >= 0.9, or waist-to-height ratio >= 0.5 was significantly associated with a 0.27 (95% confidence interval: 0.15, 0.38) mL, 14.47 (3.60, 25.34) x 10(6), 7.06 (0.46, 13.76) x 10(6), and 6.80 (0.42, 13.18) x 10(6) reduction in semen volume, total sperm number, total motile sperm number, and total progressive motile sperm number, respectively, and a 53% (10%, 112%) increase in odds of below the World Health Organization 2010 reference value for semen volume. These associations did not significantly vary across age. Similar results were observed for central obesity defined using each of the three indicators, except that subjects with a waist circumference >= 90 cm had a slightly higher total motility (estimated change: 1.30%; 95% confidence interval: 0.27%, 2.34%) and progressive motility (estimated change: 1.27%; 95% confidence interval: 0.23%, 2.31%). Discussion and conclusionWe found that central obesity was significantly associated with a reduction in semen volume, total sperm number, total motile sperm number, and total progressive motile sperm number. Future studies are warranted to confirm our results in other regions and populations.