Waist circumference and all-cause mortality in a large US cohort

Waist circumference (WC), a measure of abdominal obesity, is associated with higher mortality independent of body mass index (BMI). Less is known about the association between WC and mortality within categories of BMI or for the very high levels of WC that are now common.

We examined the association between WC and mortality among 48,500 men and 56,343 women, 50 years or older, in the Cancer Prevention Study II Nutrition Cohort. A total of 9315 men and 5332 women died between 1997 and the end of follow-up in 2006.

After adjustment for BMI and other risk factors, very high levels of WC were associated with an approximately 2-fold higher risk of mortality in men and women (among men, relative risk [RR]=2.02; 95% confidence interval [CI], 1.71-2.39 for WC>or=120 cm compared with <90 cm; among women, RR=2.36; 95% CI, 1.98-2.82 for WC>or=110 cm compared with <75 cm). The WC was positively associated with mortality within all categories of BMI. In men, a 10-cm increase in WC was associated with RRs of 1.16 (95% CI, 1.09-1.23), 1.18 (95% CI, 1.12-1.24), and 1.21 (95% CI, 1.13-1.30) within normal (18.5 to <25), overweight (25 to <30), and obese (>or=30) BMI categories, respectively. In women, corresponding RRs were 1.25 (95% CI, 1.18-1.32), 1.15 (95% CI, 1.08-1.22), and 1.13 (95% CI, 1.06-1.20).

These results emphasize the importance of WC as a risk factor for mortality in older adults, regardless of BMI.