HEALTH NEWS

Study Title:

Waistline and Mortality

Study Abstract

Background 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.

Methods 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.

Results 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 120 cm compared with <90 cm; among women, RR = 2.36; 95% CI, 1.98-2.82 for WC 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 (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).

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

From press release:

Individuals with a large waist circumference appear to have a greater risk of dying from any cause over a nine-year period, according to a report in the August 9/23 issue of Archives of Internal Medicine, one of the JAMA/Archives journals.

Having a large waist circumference has previously been associated with inflammation, insulin resistance, type 2 diabetes, abnormal cholesterol levels and heart disease, according to background information in the article. This may be because waist circumference is strongly correlated with fat tissue in the viscera -- surrounding the organs in the abdomen -- which is thought to be more dangerous than fat tissue under the skin.

Eric J. Jacobs, Ph.D., and colleagues at the American Cancer Society, Atlanta, examined the association between waist circumference and risk of death among 48,500 men and 56,343 women age 50 and older (median or midpoint age, 69 years in men and 67 years in women). All had participated in the Cancer Prevention Study II Nutrition Cohort, for which they completed a mailed questionnaire about demographic, medical and behavioral factors in 1992 or 1993 and provided information about weight and waist circumference in 1997. Deaths and their causes were tracked through the National Death Index until Dec. 31, 2006; a total of 9,315 men and 5,332 women died during this timeframe.

After adjusting for body mass index (BMI) and other risk factors, very large waists (120 centimeters or 47 inches or larger in men, and 110 centimeters or 42 inches or larger in women) were associated with approximately twice the risk of death during the study period. A larger waist was associated with higher risk of death across all categories of BMI, including normal weight, overweight and obese; however, among women, the association was strongest for those at a normal weight.

"The reason for the stronger association between waist circumference and mortality among women with low BMI in our study is unclear," the authors write. "Future detailed analyses of the relationship between waist circumference and visceral adipose tissue or measures of insulin resistance within categories of BMI could identify biological reasons for potential differences in the strength of the association between waist circumference and mortality."

The results may affect the development of future guidelines for obesity, the authors suggest. "Currently available clinical guidelines from the National Institutes of Health are based on evidence from the 1990s," they write. "These guidelines recommend that waist circumference be used to identify increased disease risk only among individuals in the overweight and obese categories of BMI. In addition, the NIH guidelines recommend weight loss goals for all patients in the obese category of BMI (30 or greater), but they do not specifically recommend weight loss goals for abdominally obese patients (waist circumference of 88 centimeters or larger in women or 102 centimeters or larger in men) who are in the normal or overweight BMI category unless they also have two or more cardiovascular risk factors or a desire to lose weight."

Study Information

Eric J. Jacobs, PhD; Christina C. Newton, MSPH; Yiting Wang, PhD; Alpa V. Patel, PhD; Marjorie L. McCullough, ScD; Peter T. Campbell, PhD; Michael J. Thun, MD; Susan M. Gapstur, PhD .
Waist Circumference and All-Cause Mortality in a Large US Cohort
Arch Intern Med.
2010 August