To explore the association between nighttime sleep duration and semen quality.

By using a cross-sectional study, 3357 men were investigated by questionnaire for nighttime sleep duration, the time of falling asleep and falling asleep duration in the Reproductive Center of Shenzhen People's Hospital from August 2017 to August 2018. Semen quality parameters were obtained by computer-aided semen analysis system (CASA). Multiple linear regression was used to analyze the relationship between nighttime sleep duration and semen quality parameters. According to age and body mass index (BMI) stratification, the relationship between nighttime sleep duration and semen quality parameters was further discussed.

Compared with males with nighttime sleep duration between 6-8 h, the sperm progressive motility and total motility were 49.15% and 59.49%, respectively, which were significantly lower in the males with nighttime sleep duration≥8 h after adjusting for age, BMI, abstinence time, exercise, drinking and smoking, with regression coefficients, β=-3.16, 95% confidence interval (CI)=-5.77--0.55 and β=-3.22, 95% CI=-5.93--0.51, respectively. Compared with the shortest duration of falling asleep group (<10 min), the increase of falling asleep duration was related to the decrease of sperm progressive motility (P=0.045). The total sperm motility of falling asleep duration between 31-60 min group was also significantly lower than that of the shortest falling asleep duration group （β=-3.80, 95% CI=-6.54--1.06, P=0.007）. Further stratification analysis showed that among the subjects aged 35 to 39 years, the sperm progressive motility of men with nighttime sleep duration less than 6 h was lower than that of 6-8 h group (β=-4.01, 95% CI=-7.84-0.18, P=0.04). And among the subjects aged more than 40 years, the total sperm number of the men who slept ≥8 h at night was lower than that of the men with nighttime sleep duration between 6-8 h （percentage changes: -47.84%, 95% CI=-72.29%--2.19%, P=0.04）. The progressive and total sperm motility of men with BMI≥24 kg/m² and nighttime sleep duration ≥8 h were lower than those with BMI≥24 kg/m² in 6-8 h nighttime sleep duration group, and the corresponding regression coefficients were β=-5.75, 95%CI=-10.40--1.10, P=0.02 and β=-6.85, 95% CI=-11.69--2.00, P=0.01.

In men ≥40 years old or BMI≥24 kg/m², the nighttime sleep duration ≥8 h were associated with the decreased sperm progressive motility and total motility.

Age; Body mass index; Semen quality; Nighttime sleep duration