Waist circumference and body composition in relation to all-cause mortality in middle-aged men and women

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Abstract
Waist circumference is directly related to all-cause mortality when adjusted for body mass index (BMI). Body fat and fat-free body mass, when mutually adjusted, show with increasing values an increasing and decreasing relation to all-cause mortality. We investigated the association of waist circumference and body composition (body fat and fat-free mass), mutually adjusted, to all-cause mortality. A Danish prospective cohort study with a median follow-up period of 5.8 y. In all, 27 178 men and 29 875 women, born in Denmark, aged 50–64 y, and without diagnosis of cancer at the time of invitation. Waist circumference and body composition estimated from impedance measurements. Cox's regression models were used to estimate the mortality rate ratios (RR). Waist circumference was strongly associated with all-cause mortality after adjustment for body composition; the mortality RR was 1.36 (95% confidence intervals (CI): 1.22–1.52) times higher per 10% larger waist circumference among men and 1.30 (95% CI: 1.17–1.44) times higher among women. Adjustment for waist circumference eliminated the association between high values of the body fat mass index (BFMI) and all-cause mortality. The association between fat-free mass index (FFMI) and mortality remained unaltered. Waist circumference accounted for the mortality risk associated with excess body fat and not fat-free mass. Waist circumference remained strongly and directly associated with all-cause mortality when adjusted for total body fat in middle-aged men and women, suggesting that the increased mortality risk related to excess body fat is mainly due to abdominal adiposity.