INTRODUCTION: The effect of obesity on mortality in people with metabolic syndrome (MetS) risk factors, but without pre-existing diabetes; hypertension; or cardiovascular disease (CVD), is uncertain. The purpose of this study is to investigate the effect of obesity and MetS risk factors on CVD and all-cause mortality in an Asian cohort.
METHODS: This retrospective study included 275,867 Koreans (56.6% men) who participated in an occupational health program between 2002 and 2009. At baseline, four groups were defined, according to the absence/presence of obesity (defined by BMI < or ≥25, respectively) and zero or one or more MetS features, respectively: metabolically healthy non-obese (MHNO; reference group); metabolically healthy obese (MHO); metabolically unhealthy obese (MUO); and metabolically unhealthy non-obese (MUNO). Hazard ratios (HRs) and 95% CIs for CVD and all-cause mortality at follow-up were estimated using Cox proportional hazards models.
RESULTS: During follow-up, 1,060 deaths (187 from CVD) occurred. After adjusting for age, sex, alcohol intake, exercise, and educational status, CVD mortality risk was not increased in the MHO group (HR=0.50, 95% CI=0.15, 1.66), whereas risk was increased in the MUO and MUNO groups (HR=1.81, 95% CI=1.12, 2.91; HR=1.84, 95% CI=1.15, 2.92, respectively). HRs for all-cause mortality in both obese groups were not different from the reference group. When subjects with prior diabetes, CVD, and hypertension were excluded, CVD mortality was not significantly different in the MUO and MUNO groups from the reference group.
CONCLUSIONS: Comorbid diabetes, hypertension, or CVD explain much of the increased risk of CVD mortality in obese individuals.