Risk of Incident Dementia According to Metabolic Health and Obesity Status in Late Life: A Population-Based Cohort Study

Context: The risk for dementia among subjects who are obese with normal metabolic profiles, or called metabolically healthy obese (MHO), remains uninvestigated. Objective: To determine the association between late-life metabolic health and obesity status and risk of incident dementia. Design: Retrospective cohort study. Setting: The National Health Insurance System, Republic of Korea. Patients: A total of 12,296,863 adults. 50 years old who underwent health examinations from 2009 to 2012 without baseline history of dementia. Main Outcome Measure: Incident overall dementia, Alzheimer's disease (AD), and vascular dementia (VaD). Results: Among subjects >= 60 years old, 363,932 (6.4%) developed dementia during a median follow-up of 65 months (interquartile range 51 to 74 months). The MHO group showed the lowest incidence of overall dementia [hazard ratio (HR) 0.85; 95% CI, 0.84 to 0.86] and AD (HR0.87; 95% CI, 0.86 to 0.88), but not VaD, compared with the metabolically healthy nonobese group. All components of metabolic syndrome except obesity significantly elevated the risk of dementia, and these associations were more pronounced in VaD. In particular, being underweight dramatically increased the risk of dementia. Conclusions: The MHO phenotype in late life demonstrated lower risk of overall dementia and AD but not VaD. Additional studies in other populations are warranted to elucidate current results and may predict individuals most at risk for developing dementia.