A systematic review and meta-analysis of 104 studies involving 341,471 participants found a weak association between baseline physical activity and follow-up global cognition, with evidence also in episodic memory and verbal fluency. The association was not significantly influenced by study quality, follow-up length, baseline age, or adjustment for preceding cognition. Physical activity showed a small but significant association with follow-up global cognition and changes in global cognition, but no clear dose-response relationship. The study suggests that physical activity may modestly delay cognitive decline at a population level, though the effect is small. The findings highlight the need for further high-quality research to confirm these results and better understand the relationship between physical activity and cognitive decline.A systematic review and meta-analysis of 104 studies involving 341,471 participants found a weak association between baseline physical activity and follow-up global cognition, with evidence also in episodic memory and verbal fluency. The association was not significantly influenced by study quality, follow-up length, baseline age, or adjustment for preceding cognition. Physical activity showed a small but significant association with follow-up global cognition and changes in global cognition, but no clear dose-response relationship. The study suggests that physical activity may modestly delay cognitive decline at a population level, though the effect is small. The findings highlight the need for further high-quality research to confirm these results and better understand the relationship between physical activity and cognitive decline.