The association between sleep and fecundability: a Danish preconception cohort study.
Level 3 - non-randomized controlled study
Prospective cohort study
PubMed 40139814 · doi:10.1093/eurpub/ckaf039
What was done
Data from a Danish preconception cohort of 10,475 females aged 18–45 years attempting to conceive were analyzed. Baseline questionnaires assessed daily sleep duration (hours/day), frequency of trouble sleeping (never, sometimes, approx. 50% of the time, most of the time), and work schedule (day, evening, shift, night work). Pregnancy status was tracked via follow-up questionnaires every 8 weeks for up to 12 months. Proportional probabilities regression models estimated fecundability ratios (FRs), adjusted for potential confounders.
What was found
Compared to 8 hours/day of sleep, FRs were 0.94 (95% CI, 0.83–1.08) for ≤6 hours/day, 0.97 (95% CI, 0.89–1.06) for 7 hours/day, and 0.96 (95% CI, 0.81–1.13) for ≥9 hours/day. Relative to no trouble sleeping, FRs were 1.00 (95% CI, 0.94–1.06) for trouble sleeping sometimes, 0.94 (95% CI, 0.86–1.03) for trouble sleeping ~50% of the time, and 0.95 (95% CI, 0.82–1.10) for trouble sleeping most of the time. Compared to day work, FRs were 1.12 (95% CI, 1.04–1.20) for shift work, 0.77 (95% CI, 0.49–1.22) for night work, and 1.10 (95% CI, 0.91–1.33) for evening work.
Why it matters
In a large preconception cohort, neither self-reported sleep duration nor trouble sleeping showed an appreciable link to per-cycle conception rates, suggesting routine variation in sleep habits does not substantially impact fecundability.
Limits
Sleep duration, quality, and job timing were self-reported at baseline rather than objectively measured. Night work estimates were imprecise with wide confidence intervals. Residual or unmeasured confounding and exposure misclassification remain possible.
Cited by
- contradicts Self-reporting poor sleep is associated with double the rate of infertility.