Recent clinical guidelines on the health risks of obesity use body mass index (BMI; calculated as weight in kilograms divided by the square of height in meters) and waist circumference, but the waist-hip ratio may provide independent information.
To assess the joint and relative associations of BMI, waist circumference, and waist-hip ratio with multiple disease end points, we conducted a prospective cohort study of 31,702 Iowa women, aged 55 to 69 years and free of cancer, heart disease, and diabetes, assembled by random sampling and mail survey in 1986. Study end points were total and cause-specific mortality and incidence of site-specific cancers and self-reported diabetes, hypertension, and hip fracture over 11 to 12 years.
The waist-hip ratio was the best anthropometric predictor of total mortality, with the multivariable-adjusted relative risk for quintile 5 vs 1 of 1.2 (95% confidence interval, 1.1-1.4), compared with 0.91 (95% confidence interval, 0.8-1.0) for BMI and 1.1 (95% confidence interval, 1.0-1.3) for waist circumference. The waist-hip ratio was also associated positively with mortality from coronary heart disease, other cardiovascular diseases, cancer, and other causes. The waist-hip ratio was associated less consistently than BMI or waist circumference with cancer incidence. All anthropometric indexes were associated with incidence of diabetes and hypertension. For example, women simultaneously in the highest quintiles of BMI and waist-hip ratio had a relative risk of diabetes of 29 (95% confidence interval, 18-46) vs women in the lowest combined quintiles.
The waist-hip ratio offers additional prognostic information beyond BMI and waist circumference.