A prospective study of male physical activity and fecundability

• Published in: Human reproduction (Oxford) 2024-12
• Main Authors: Wise, Lauren A, Wang, Tanran R, Ulrichsen, Sinna Pilgaard, Krivorotko, Dmitrii, Mikkelsen, Ellen M, Kuriyama, Andrea S, Laursen, Anne Sofie Dam, Jørgensen, Marie Dahl, Eisenberg, Michael L, Rothman, Kenneth J, Sorensen, Henrik Toft, Hatch, Elizabeth E
• Format: Article
• Language: English
• ISSN: 1460-2350; 1460-2350
• DOI: 10.1093/humrep/deae275

To what extent is male physical activity (PA) associated with fecundability (per-cycle probability of conception)? Preconception levels of vigorous, moderate, or total PA were not consistently associated with fecundability across Danish and North American cohorts, but there was suggestive evidence that bicycling with a 'soft, comfort seat' was associated with reduced fecundability in both cohorts, especially among males with greater BMI. Among males, some studies indicate that moderate PA might improve fertility, whereas vigorous PA, especially bicycling, might be detrimental. We assessed the association between male PA and fecundability among couples participating in two preconception cohort studies: SnartForaeldre.dk (SF) in Denmark (2011-2023) and Pregnancy Study Online (PRESTO) in North America (2013-2024). We restricted analyses to 4921 males (1088 in SF and 3833 in PRESTO) who had been trying to conceive with their partners for ≤6 cycles at enrollment. At baseline, male partners reported data on medical history, lifestyle, behavioral, anthropometric factors, and their PA levels using different instruments [SF: International Physical Activity Questionnaire (IPAQ); PRESTO: average annual hours/week and type]. Both cohorts included additional questions on bicycling (frequency, bike seat type). After linking couple data at baseline, the female partner completed follow-up questionnaires to update their pregnancy status every 8 weeks for 12 months or until conception, whichever occurred first. We used proportional probabilities regression models to estimate fecundability ratios (FRs) and 95% CIs, controlling for potential confounders. Average hours/week of vigorous PA, moderate PA, and total metabolic equivalents of task were generally inversely associated with fecundability in SF, but not PRESTO. While there was little association with bicycling overall in either cohort, we observed an inverse association for bicycling using a 'soft, comfort seat' (≥3 vs 0 h/week: SF: FR = 0.75, 95% CI: 0.53-1.05; PRESTO: FR = 0.81, 95% CI: 0.62-1.07) but not a 'hard, racing-style seat' (≥3 vs 0 h/week: SF: FR = 1.16, 95% CI: 0.95-1.41; PRESTO: FR = 1.06, 95% CI: 0.89-1.28). Among males with BMI ≥25 kg/m2, associations with bicycling using a 'soft, comfort seat' were similar or stronger (≥3 vs 0 h/week: SF: FR = 0.75, 95% CI: 0.45-1.24; PRESTO: FR = 0.73, 95% CI: 0.52-1.03). Misclassification of PA was likely the most important study limitation because we ascertained PA o