Systematic review and meta‐analysis of the association between childhood physical activity and age at menarche

AIM: To systematically appraise and summarise published evidence on the association between childhood physical activity (PA) and subsequent age at menarche (AAM). METHODS: We searched PubMed (1990–2018) for studies that reported the relationship between childhood PA and AAM. We performed tabular synthesis of population‐based studies and a random‐effects meta‐analysis of results of athlete/nonathlete studies. RESULTS: One randomised controlled trial was identified, in which an intervention to prevent obesity reduced the likelihood of menarche during the two‐year study period (relative risk: 0.75, 95% CI: 0.66–0.87; n = 422 girls). One of five prospective cohort studies (total n = 4492) reported a significant association between self‐reported PA duration and subsequent menarche timing. Four of five historical cohort studies (total n = 89 470) reported significant associations between recalled premenarcheal PA and later AAM. Meta‐analysis across 12 athlete/nonathlete studies showed that menarche occurred 1.13 years later (95% CI: 0.80–1.47) in athletes compared to nonathletes. CONCLUSION: These findings suggest that AAM is a behaviourally modifiable trait. However, the quality of reported population‐based study evidence is low and estimation of the true relationship between childhood PA and AAM is likely confounded by concomitant changes in diet and lifestyle behaviours.