Associations between physical activity and health outcomes in clinical and non-clinical populations: A systematic meta-umbrella review

Background: The beneficial effect of physical activity in various health conditions is recognised, but the consistency and magnitude of its outcomes remain debated. Therefore, we aimed to chart the evidence of the association between physical activity and health outcomes in clinical and non-clinical populations. Methods: : We conducted a meta-umbrella review using a semiquantitative and descriptive analysis. We searched PubMed/MEDLINE, PsycINFO, and CINHAL databases from inception to February 28, 2023, for umbrella reviews that evaluated the relationship between physical activity and health outcomes using validated methods to assess evidence levels. Two reviewers independently screened, extracted data, and assessed quality of the umbrella reviews. The overlap analysis of component meta-analyses within the umbrella reviews was performed using the Corrected Covered Area (CCA) method. To ensure consistency, pooled effect estimates were converted to equivalent odds ratios (eORs). Results: : Sixteen umbrella reviews with a total of 130 statistically significant associations were included. The sole risk-demonstrating association, supported by convincing evidence, was between intensive sports and atrial fibrillation (eOR=1.64, 95%CI=1.10-2.43). The strongest protective associations, supported by convincing and highly suggestive evidence, were between any physical activity and the incidence of Parkinson's disease (eOR=0.66, 95%CI=0.57-0.78), Alzheimer's disease (eOR=0.62, 95%CI=0.52-0.72), cognitive decline (eOR=0.67; 95%CI=0.57-0.78), breast cancer incidence (eOR=0.87, 95%CI=0.84-0.90), endometrial cancer incidence (eOR=0.79, 95%CI=0.74-0.85), and between recreational physical activity and the incidence/mortality of cancer (eOR=0.70, 95%CI=0.60-0.83). The remaining ones demonstrated lower levels of evidence, while 60 (46.2%) of those exhibited multiple levels of evidence, displaying a lack of consistency. Conclusion: Despite the inconsistent evidence across associations, the contribution of regular physical activity to maintaining both physical and mental health cannot be underestimated, particularly when it comes to cognitive and cancer outcomes. The association between intensive sports and potential risk of atrial fibrillation requires further consideration though.