Adiposity and mortality in Korean adults: A population-based prospective cohort study

Background: The Asia-Pacific obesity classification recommends using lower BMI cutoffs in Asians compared with those in Western populations. However, the supporting evidence is scarce and little is known about the exact shape of the relations between adiposity and mortality in Asians. Objectives: We investigated the relations of BMI (in kg/m²), waist circumference, and predicted body fat mass with mortality using a population-based prospective cohort of Korean men and women. Methods: This analysis included 44,060 Korea National Health and Nutrition Examination Survey 2007–2014 participants who agreed to mortality follow-up through 31 December, 2016. At baseline, height, weight, and waist circumference were measured. Using DXA data, we derived predicted body fat and fat-free mass. Cox proportional hazards models were used to estimate HRs and 95% CIs for the associations with mortality, adjusting for potential confounders. We tested for nonlinearity using the likelihood ratio test comparing nonlinear restricted cubic spline models with linear models. Results: During ≤9.5 y of follow-up, 1682 deaths were identified. The relations of BMI with all-cause and cardiovascular mortality were J-shaped with the nadir at BMI = 25.0–29.9 (P-nonlinearity < 0.001). Among participants without a history of cancer or cardiovascular disease, waist circumference (≥95 compared with 75.0–79.9 cm: HR: 2.10; 95% CI: 1.54, 2.86) and predicted body fat mass (highest compared with lowest sextiles: 2.55; 95% CI: 1.60, 4.06) were positively associated with all-cause mortality (all P-nonlinearity ≤ 0.03), as well as cancer and cardiovascular mortality. The highest mortality was observed among participants who had both high predicted fat mass and low fat-free mass. Conclusions: Our data suggest a strong positive association between adiposity and mortality in a population without pre-existing disease. We observed the lowest mortality at BMI = 25.0–29.9, suggesting that the current cutoff for overweight (BMI ≥23) may require re-evaluation and that BMI alone may not be a useful measure for indicating adiposity in Asians.