Leisure time physical activity and mortality: detailed pooled dose-response relationship Strong SportObservational evidenceReverse causation risk Observational study Highest vs lowest activity roughly 25–35% lower mortality in major prospective meta-analyses Causal status: Mostly association; causal support substantial but mortality RCT evidence limited Reliability / bias notes: Reverse causation; questionnaire error; healthy-user bias Arem et al · JAMA Intern Med · 2015 · PMID 25844730 Read the study →