A North American preconception study of sleep health and semen quality

STUDY QUESTION: To what extent are self-reported sleep health measures associated with semen quality? SUMMARY ANSWER: Poor sleep health-including short and long sleep durations, increased frequency of sleep trouble, and poor sleep quality-was associated with reduced sperm concentration, total sperm count, and total motile sperm count, and, in the case of short sleep duration and increased frequency of sleep trouble, reduced semen volume. WHAT IS KNOWN ALREADY: Semen quality has declined over the past several decades. Sleep health may affect semen quality through multiple pathways, including endocrine dysfunction, and population-based prospective studies of the association are scarce. STUDY DESIGN, SIZE, DURATION: We analyzed cross-sectional data from 690 male participants (1247 semen samples) aged ≥21 years at enrollment (2015-2023) in Pregnancy Study Online, a North American preconception cohort study. PARTICIPANTS/MATERIALS, SETTING, METHODS: At baseline, participants provided self-reported data on sleep duration in the past month and frequency of sleep trouble in the previous 2 weeks. A subset of participants completed the Pittsburgh Sleep Quality Index. We used generalized estimating equations (GEE) models to estimate mean percentage differences (%D) and 95% CIs for the associations of sleep health with semen parameters (semen volume, sperm concentration, percent motility), ascertained using a validated at-home semen testing kit. We also used GEE models to estimate prevalence ratios for poor semen quality (low vs normal) based on World Health Organization (WHO) standards. MAIN RESULTS AND THE ROLE OF CHANCE: Comparing sleep durations of <6 vs 7-8.9 h/day, %Ds (95% CIs) were -11.3% (-23.6%, 1.1%), -16.4% (-45.0%, 26.9%), -27.1% (-53.1%, 13.2%), and -20.0% (-50.3%, 28.8%) for semen volume, sperm concentration, total sperm count, and total motile sperm count, respectively. We observed similar associations for ≥9 vs 7-8.9 h/day and sperm concentration (-14.4% [-44.9%, 33.0%]), total sperm count (-13.9% [-44.1%, 32.7%]), and total motile sperm count (-6.8% [-42.1%, 49.9%]). Comparing sleep trouble >50% of the time vs never, %Ds (95% CIs) were -3.3% (-12.0%, 5.4%), -11.9% (-29.9%, 10.8%), -16.2% (-34.3%, 7.0%), and -16.9% (-37.3%, 9.9%) for semen volume, sperm concentration, total sperm count, and total motile sperm count, respectively. Comparing global Pittsburgh Sleep Quality Index scores of >5 (poor sleep quality) vs ≤5 (good sleep quality), %Ds (95% CIs) were -18.1% (-33.5%, 0.9%), -19.2% (-34.6%, -0.1%), and -16.3% (-33.5%, 5.4%) for sperm concentration, total sperm count, and total motile sperm count, respectively. Analyses based on WHO semen quality standards showed consistent results. LIMITATIONS, REASONS FOR CAUTION: Non-differential misclassification of sleep health was possible due to our reliance on self-reported data collected at a single point in time. Non-differential misclassification of semen quality was also possible, as participants used an at-home semen testing kit to measure semen parameters. We cannot rule out bias due to residual or unmeasured confounding. Given that the study population was restricted to pregnancy planners who enrolled via the Internet, our findings may not be generalizable to other populations. WIDER IMPLICATIONS OF THE FINDINGS: Our findings are generally consistent with previous research, supporting a relationship between poor sleep health and worse semen quality. We analyzed data from a population-based sample of pregnancy planners, which overcomes limitations from most prior studies that relied on convenience samples of infertile couples or sperm donors. These findings may inform sleep interventions to improve reproductive health outcomes. STUDY FUNDING/COMPETING INTEREST(S): This work was supported by the following grants from the Eunice Kennedy Shriver National Institute of Child Health and Human Development, USA: R01HD086742, R01HD105863, R21HD094322. J.J.Y. is an employee of Optum and owns stock in UnitedHealth Group. G.J.S. is an employee of and holds stock in Labcorp, which manufactures the male fertility testing kits used in this study. He is also a co-inventor on multiple patents related to the male fertility testing kits reported in this manuscript: US #10 376 877, US #11 471 881, and US #11 714 034. M.L.E. is an advisor for Doveras, Hannah, Next, Illumicell, Legacy, and HisTurn, which includes a small equity grant of options. S.M.B. has received consulting fees from Idorsia Pharmaceuticals and Apnimed in the past 12 months, participated in a Data Safety Monitoring Board or Advisory Board for PCORI and AHRQ, and served in a leadership role for the Sleep Research Society and American Academy of Sleep Medicine. All other authors have no disclosures to report. TRIAL REGISTRATION NUMBER: N/A.