Association of Normal-Weight Central Obesity With All-Cause and Cause-Specific Mortality Among Postmenopausal Women

Key Points

Question

How is normal-weight central obesity associated with risk of mortality compared with other anthropometric phenotypes?

Findings

In this cohort study of 156 624 postmenopausal US women enrolled in the Women’s Health Initiative study, normal-weight central obesity was associated with higher risk of all-cause, cardiovascular disease, and cancer mortality compared with normal weight without central obesity. The magnitude of this association was similar to that of obesity with central obesity and higher than that of other anthropometric phenotypes defined by body mass index and waist circumference.

Meaning

Normal-weight central obesity is an underrecognized, high-risk phenotype for mortality.

Abstract

This cohort study uses data from women enrolled in the Women’s Health Initiative (WHI) to examine the associations of normal-weight central obesity with all-cause and cause-specific mortality among postmenopausal women in the United States.

Abstract

Importance

Current public health guidelines for obesity prevention and control focus on promoting a normal body mass index (BMI), rarely addressing central obesity, which is reflected by high waist circumference (WC) and common in the general population. Studies of the association of normal-weight central obesity with long-term health outcomes are sparse.

Objective

To examine associations of normal-weight central obesity with all-cause and cause-specific mortality in postmenopausal women in the United States.

Design, Setting, and Participants

A nationwide prospective cohort study of 156 624 postmenopausal women enrolled in the Women’s Health Initiative at 40 clinical centers in the United States between 1993 and 1998. These women were observed through February 2017. Data analysis was performed from September 15, 2017, to March 13, 2019.

Exposures

Different combinations of BMI (calculated as weight in kilograms divided by height in meters squared; normal weight: BMI, 18.5-24.9; overweight: BMI, 25.0-29.9; and obesity: BMI, ≥30) and WC (normal: WC, ≤88 cm and high: WC, >88 cm).

Main Outcomes and Measures

Mortality from all causes, cardiovascular disease, and cancer.

Results

Of the 156 624 women (mean [SD] age, 63.2 [7.2] years), during 2 811 187 person-years of follow-up, 43 838 deaths occurred, including 12 965 deaths from cardiovascular disease (29.6%) and 11 828 deaths from cancer (27.0%). Compared with women with normal weight and no central obesity and adjusted for demographic characteristics, socioeconomic status, lifestyle factors, and hormone use, the hazard ratio for all-cause mortality was 1.31 (95% CI, 1.20-1.42) among women with normal weight and central obesity, 0.91 (95% CI, 0.89-0.94) among women with overweight and no central obesity, 1.16 (95% CI, 1.13-1.20) for women with overweight and central obesity, 0.93 (95% CI, 0.89-0.94) for women with obesity and no central obesity, and 1.30 (95% CI, 1.27-1.34) for women with obesity and central obesity. Compared with normal weight without central obesity, normal-weight central obesity was associated with higher risk of cardiovascular disease mortality (hazard ratio, 1.25; 95% CI, 1.05-1.46) and cancer mortality (hazard ratio, 1.20; 95% CI, 1.01-1.43).

Conclusions and Relevance

Normal-weight central obesity in women was associated with excess risk of mortality, similar to that of women with BMI-defined obesity with central obesity. These findings underscore the need for future public health guidelines to include the prevention and control of central obesity, even in individuals with normal BMI.