Association of sleep disturbances with reduced semen quality: a cross-sectional study among 953 healthy young Danish men.
Level 4 - case-series / case-control
Cross-sectional observational study
PubMed 23568594 · doi:10.1093/aje/kws420
What was done
A cross-sectional study analyzed 953 young Danish men recruited from the general population during military fitness examinations in Copenhagen between January 2008 and June 2011. Each participant provided a semen sample, underwent a physical examination measuring testis size, gave a blood sample, and completed a questionnaire. Sleep disturbances over the preceding 4 weeks were assessed using a modified 4-item version of the Karolinska Sleep Questionnaire.
What was found
Sleep disturbances showed an inverse U-shaped association with sperm concentration, total sperm count, percent motile spermatozoa, percent morphologically normal spermatozoa, and testis size. Men with high sleep disturbance scores (>50) had a 29% (95% CI: 2, 48) lower adjusted sperm concentration and 1.6 (95% CI: 0.3, 3.0) percentage points fewer morphologically normal spermatozoa compared to men with a sleep score of 11-20.
Why it matters
This study provides early population-level evidence linking self-reported sleep disturbances with reduced semen parameters and smaller testis size in young men.
Limits
The cross-sectional design precludes establishing causality or temporal order. Sleep disturbances were assessed via a brief subjective questionnaire rather than objective sleep metrics (such as polysomnography or actigraphy), and semen parameters were based on single samples. The sample was restricted to young Danish men undergoing military fitness evaluations.
Cited by
- supports Men who get less sleep exhibit lower testosterone levels and lower sperm counts.