Cumulative burden of lifestyle risk factors on Alzheimer's disease in older Korean adults: A nationwide retrospective cohort study

BackgroundPrevalence of Alzheimer's disease (AD) is increasing worldwide. Certain lifestyles are associated with AD; however, the long-term combined effects of lifestyle risk factors on AD have not been investigated.ObjectiveWe investigated the cumulative effect of lifestyle risk factors over an 8-year period on AD among older Korean adults.MethodsWe analyzed 142,763 participants aged ≥65 years using the National Health Insurance Service-Senior Cohort. Lifestyle factors (smoking status, alcohol consumption, and physical activity) were evaluated in 4 consecutive phases of health checkups (2002-2003, 2004-2005, 2006-2007, and 2008-2009). Each participant's overall lifestyle risk score during these phases was calculated by scoring a single poor lifestyle factor in each phase as 1, resulting in a score range of 0 to 12. Hazard ratios (HRs) for AD according to lifestyle risk scores were calculated.ResultsThe risk of AD increased with the number of poor lifestyle factors at baseline. Furthermore, the risk of AD increased as the lifestyle risk scores evaluated during the 4 phases increased. In men, compared to score 0-1, the HRs (95% CIs) for AD were 1.25 (1.06-1.47), 1.30 (1.11-1.51), and 1.40 (1.20-1.63) for scores 2-3, 4-5, and 6-12, while in women, these were 1.34 (1.14-1.56), 1.41 (1.21-1.64), and 1.54 (1.23-1.94).ConclusionsThe AD risk increased with the cumulative burden of poor lifestyle during the 8 year-period. It is important to maintain as many healthy lifestyles as possible to reduce the risk of AD.