Higher mortality in metabolically obese normal-weight people than in metabolically healthy obese subjects in elderly Koreans

Objective The purpose of this study was to investigate the impact of body mass index (BMI) and the presence of metabolic syndrome (MetS) on all-cause and cardiovascular mortality in elderly Korean men and women, and especially to compare metabolically obese normal-weight (MONW) and metabolically healthy obese (MHO) subjects. Patients and methods A total of 2317 elderly people (over 60 years of age) were studied using follow-up data from the South-West Seoul (SWS) Study, a prospective cohort study. Mortality from all causes and cardiovascular disease (CVD) were evaluated according to the combination of the presence or absence of MetS and Asian-specific body mass index (BMI) criteria (BMI <23 kg/m²; normal weight, BMI 23-24·9 kg/m²; overweight, BMI ≥25 kg/m²; obesity). Results During a median follow-up of 10·3 years, 393 subjects died, including 126 from CVD. Among subjects with MetS, all-cause and CVD mortality were significantly higher in normal-weight subjects than overweight or obese individuals in Cox proportional-hazard models adjusted for confounding factors. Furthermore, among six groups with various MetS/BMI combinations, MONW individuals had the highest risk, whereas overweight subjects without MetS had the lowest risk of death from all causes and CVD [HR = 2·2 (95% CI = 1·4-3·4), HR = 3·0 (95% CI = 1·4-6·6) respectively]. Interestingly, all-cause mortality was significantly higher in MONW than MHO individuals. Conclusions In contrast to MHO subjects, elderly individuals with the MONW phenotype exhibited greater all-cause mortality during 10 years of follow-up.