Association Between Physical Activity and the Risk of Dementia Among Patients With Depression: A Nationwide Cohort Study

Objective This study investigates the impact of changes in physical activity (PA) on the risk of developing dementia in individuals diagnosed with depression, using a large-scale, retrospective national cohort dataset. Methods Using a cohort data from the National Health Insurance of South Korea, 1,291,706 clinically depressed subjects were analyzed to assess the relationship between PA and dementia onset. Subjects were classified into four groups—“never,” “beginning,” “discontinuation,” or “maintenance”—based on their PA status before and after the diagnosis of depression. Hazard ratios with confidence intervals were calculated to determine the risk across different PA status groups. Results Among the total sample, 58,934 (4.56%) were newly diagnosed with dementia during the follow-up period. Our findings demonstrated that those who maintained PA post-diagnosis had the lowest risk of developing dementia. Also, beginning PA post-diagnosis is associated with a significantly lower risk of developing dementia compared to those who remained inactive or discontinued PA. Subgroup analyses indicated that the protective effect of PA against dementia is more pronounced in women than in men. Conclusion Consistent engagement in PA, particularly after the onset of depression, is associated with a reduced risk of dementia. These findings underscore the importance of PA as a potential intervention for mitigating cognitive decline in depressed individuals.