Male sleep duration and fecundability in a North American preconception cohort study.

OBJECTIVE: To evaluate prospectively the association between male sleep duration and fecundability.

DESIGN: Pregnancy Online Study (PRESTO), a Web-based prospective cohort study of North American couples enrolled during the preconception period (2013-2017).

SETTING: Not applicable.

PATIENT(S): Male participants were aged ≥21 years; female participants were aged 21-45 years.

INTERVENTION(S): None.

MAIN OUTCOME MEASURE(S): At enrollment, men reported their average nightly sleep duration in the previous month. Pregnancy status was updated on female follow-up questionnaires every 8 weeks for up to 12 months or until conception. Analyses were restricted to 1,176 couples who had been attempting to conceive for up to six cycles at enrollment. Proportional probabilities regression models were used to estimate fecundability ratios (FRs) and 95% confidence intervals (CIs), adjusting for potential confounders.

RESULT(S): Relative to 8 hours per night of sleep, multivariable-adjusted FRs for <6, 6, 7, and ≥9 hours per night of sleep were 0.62 (95% CI 0.45-0.87), 1.06 (95% CI 0.87-1.30), 0.97 (95% CI 0.81-1.17), and 0.73 (95% CI 0.46-1.15), respectively. The association between short sleep duration (<6 hours per night) and fecundability was similar among men not working nights or rotating shifts (FR 0.60, 95% CI 0.41-0.88) and among men without a history of infertility (FR 0.62, 95% CI 0.44-0.87) and was stronger among fathers (FR 0.46, 95% CI 0.28-0.76).

CONCLUSION(S): Short sleep duration in men was associated with reduced fecundability. Because male factor accounts for 50% of couple infertility, identifying modifiable determinants of infertility could provide alternatives to expensive fertility workups and treatments.