Changes in physical activity and all-cause mortality among individuals with dementia: a cohort study using the National Health Insurance Service Database in Korea.

Objective: To examine associations between the amount and changes in regular physical activity (PA) before and after diagnosis of dementia and all-cause mortality risk, and whether these associations differ by PA intensity (light, moderate or vigorous).

Methods: This retrospective cohort study used data from the Korean National Health Insurance Service Database, including 60 252 individuals newly diagnosed with dementia between 2010 and 2016 who underwent health examinations both before and after diagnosis. PA was assessed using the International Physical Activity Questionnaire-Short Form. Multivariable Cox proportional hazards regression models were used to analyse the associations between PA (amount and changes) and all-cause mortality risk.

Results: During a mean follow-up of 3.7 years, 16 431 (27.3%) deaths occurred. Higher PA levels after dementia diagnosis were associated with a dose-dependent decrease in mortality risk (p for trend <0.001). Maintaining regular PA, compared with remaining inactive, was associated with the lowest mortality risk (HR=0.71, 95% CI 0.65 to 0.79). Sustained engagement in PA of any intensity was associated with decreased mortality risk: light (HR=0.70, 95% CI 0.67 to 0.75), moderate (HR=0.74, 95% CI 0.64 to 0.86) and vigorous PA (HR=0.70, 95% CI 0.61 to 0.79). Initiating any PA intensity after dementia diagnosis was associated with at least 20% reduced mortality risk. These associations were consistent in Alzheimer's disease.

Conclusions: Maintaining or initiating regular PA, regardless of intensity, after dementia diagnosis was associated with a reduced risk of all-cause mortality. Lifestyle modifications promoting PA might offer survival benefits for individuals with dementia.