Body mass index at baseline directly predicts new-onset diabetes and to a lesser extent incident cardio-cerebrovascular events, but has a J-shaped relationship to all-cause mortality

OBJECTIVE: The prevalence of diabetes mellitus (DM), cardio-cerebrovascular diseases (CCVDs) has increased during recent decades. We aimed to investigate the relationship between body mass index (BMI) and each of several outcomes (DM, CCVDs, or mortality) based on the Korean National Health Insurance Service-Health Screening cohort. METHODS: BMI was categorized as appropriate for Asian populations, into underweight (< 18.5 kg/m(2)), normal (18.5–< 23 kg/m(2)), overweight (23–< 25 kg/m(2)), grade 1 obesity (25–< 30 kg/m(2)), grade 2 obesity (30–< 35 kg/m(2)), and grade 3 obesity (≥35 kg/m(2)). In addition, BMI was further stratified into one unit. Multivariate Cox proportional hazards regression analyses were conducted to examine the association between BMI category and the primary outcomes (DM, CCVDs, or mortality). RESULTS: A total of 311,416 individuals were included. The median follow-up was 12.5 years. Compared to normal BMI, underweight, overweight, and grade 1–3 obese individuals had a higher risk of the primary outcomes (hazard ratio [95% confidence intervals] 1.293 [1.224–1.365], 1.101 [1.073–1.129], 1.320 [1.288–1.353], 1.789 [1.689–1.897], and 2.376 [2.019–2.857], respectively, in men and 1.084 [1.010–1.163], 1.150 [1.116–1.185], 1.385 [1.346–1.425], 1.865 [1.725–2.019], and 2.472 [2.025–3.028], respectively, in women). Setting the reference BMI to 20–< 21 kg/m(2) and categorizing into one unit increment, BMI was associated with the primary outcomes in a J-shaped manner in both sexes. The risk of DM increased with higher BMI in both sexes, while all-cause mortality decreased in men with a BMI 21–< 31 kg/m(2) and women with BMI 22–< 30 kg/m(2). CONCLUSIONS: BMI was associated with all-cause mortality in a J-shaped manner in both sexes, while it was associated with risk of DM in a dose-response relationship. The relationship between BMI and the primary outcomes was J-shaped.