Methods
We assessed sleep duration (night sleep and daytime napping) and sleep quality using the Pittsburgh Sleep Quality Index (PSQI) among 842 healthy men screen as potential sperm donors. We examined sleep characteristics in relation to repeated measurements (n = 5601) of semen parameters using linear mixed-effects models.
Results
High degrees of within-individual variability were found for total and progressive sperm motility with intraclass correlation coefficient (ICC) of 0.20 and 0.22, respectively; while fair-to-good reproducibilities were observed for sperm volume, concentration, and total count (ICC = 0.54, 0.62, and 0.50, respectively). Compared to men with total sleep duration of 8.0–8.5 h/day (h/d), men who slept less than 6.0 h/d and higher than 9.0 h/d had lower sperm volume of 12% [95% confidence interval (CI): −22%, −0.68%] and 3.9% (95% CI: −7.3%, −0.44%), respectively. Compared to men with night sleep duration of 7.5–8.0 h/d, men who slept less than 6.0 h/d had lower total and progressive sperm motility of 4.4% (95 CI:−8.4%, −0.24%) and 5.0% (95% CI: −9.2%, −0.48%), respectively. Compared to men who reported good sleep quality (total PSQI score ≤5.0), those reporting poor sleep quality (total PSQI score >5.0) had lower total sperm count, total motility, and progressive motility of 8.0% (95% CI: −15%, −0.046%), 3.9% (95% CI: −6.2%, −1.5%), and 4.0% (95% CI: −6.5%, −1.4%), respectively.