Body Mass Index, Waist Circumference, and Mortality in a Large Multiethnic Postmenopausal CohortResults from the Women's Health Initiative

ObjectivesTo determine whether the relationship between anthropometric measurements of obesity and mortality varies according to age, race, and ethnicity in older women. DesignProspective cohort study of multiethnic postmenopausal women. SettingWomen's Health Initiative (WHI) observational study and clinical trials in 40 clinics. ParticipantsPostmenopausal women aged 50-79 participating in WHI (N = 161,808). MeasurementsBaseline height, weight, and waist circumference (WC) were measured, and body mass index (BMI) was calculated based on height and weight. Demographic, health, and lifestyle data from a baseline questionnaire were used as covariates. The outcome was adjudicated death (n = 18,320) during a mean follow-up of 11.4 3.2 years. ResultsHazard ratios (HRs) and 95% confidence intervals (95% CIs) indicated that ethnicity and age modified (P < .01) the relationship between obesity and mortality. Underweight was associated with higher mortality, but overweight or slight obesity was not a risk factor for mortality in most ethnic groups except for Hispanic women in the obesity I category (HR = 1.42, 95% CI = 1.04-1.95). BMI was not or was only weakly associated with mortality in individuals aged 70-79 (HR = 0.90, 95% CI = 0.85-0.95 for overweight; HR = 0.98, 95 CI = 0.92-1.06 for obese I; HR = 1.11, 95% CI = 1.00-1.23 for obese II; HR = 1.08, 95% CI = 0.92-1.26 for obese III). In contrast, higher central obesity measured using WC was consistently associated with higher mortality in all groups. ConclusionUnderweight is a significant risk factor for mortality in older women, and healthy BMI ranges may need to be specific for age, race, and ethnicity. The findings support a consistent relationship between central obesity and mortality.