Older Women With Weight Around the Middle at Higher Risk of Death

Normal-weight central obesity—better known as carrying excess stomach fat, even if not obese— is associated with a heightened risk of mortality, cardiovascular disease, and cancer among postmenopausal US women, according to a nationwide prospective cohort study published this month.

The study, published in JAMA Network Open, found that the excess risk of mortality for women with normal-weight central obesity was similar to that of women diagnosed with obesity through the calculation of body mass index (BMI), which is typically the focus of public health efforts focused on weight.

Of the 156,624 postmenopausal women who were studied, 43,838 deaths occurred, with 29% of these deaths attributed to cardiovascular disease and 27% from cancer; 1390 women had normal-weight central obesity, which accounted for 0.9% among all women and 2.6% for women with normal weight. These women were enrolled in the Women’s Health Initiative at 40 clinical centers in the United States between 1993-1998 and observed until February 2017.

Lead study author Wei Bao highlighted the underrepresentation of central obesity, which is reflected by the high waist circumference (WC) commonly found in the general population. Bao argued that while BMI measured for weight-based obesity, it ignored factors such as the body shape or body fat distribution in an individual. “The results suggest we should encourage physicians to look not only at body weight but also body shape when assessing a patient’s health risks,” said Bao.

This lack of WC measurement can mistakenly consider individuals with normal weight, but a little heavy in the middle, as normal in clinical practices. Current public health guidelines for obesity prevention maintain their focus on promoting a normal BMI, and seldom address abdominal fat reflected by WC.

Normal BMI was defined as 18.5-24.9; overweight BMI, 25.0-29.9; and obese BMI, ≥30. A normal WC was considered ≤88 cm; a high WC was >88 cm.

Data uncovered a similar risk of mortality among women with normal-weight central obesity to that of BMI-defined obesity with central obesity through comparative adjusted hazard ratios.

Compared to women with normal weight and no central obesity, the hazard ration (HR) for all-cause mortality in women with normal weight and central obesity was significantly high at 1.31 (95% CI, 1.20-1.42) and correlative to the mortality rate of other subjects:

• For women with overweight and no central obesity, the HR was 0.91 (95% CI, 0.89-0.94)
• For women with overweight and central obesity, the HR was 1.16 (95% CI, 1.13-1.20)
• For women with obesity and no central obesity, the HR was 0.93 (95% CI, 0.89-0.94)
• For women with obesity and central obesity, the HR was 1.30 (95% CI, 1.27-1.34)

These findings were further supported by the significant HR among women with of normal weight, but with belly fat, who had higher risk of death from cardiovascular disease and cancer, compared with women with normal weight and a smaller WC:

• Cardiovascular disease mortality 1.25 (95% CI, 1.05-1.46)
• Cancer mortality 1.20 (95% CI, 1.01-1.43)

The data showcase a stark contrast in mortality rate between women with normal weight and different WCs. As WC is rarely prioritized in the public health guidelines, this study reveals a crucial shortcoming for obesity prevention and control.

The study’s revelation that BMI cannot account for central obesity in individuals with a normal BMI shows a “missed opportunity for risk evaluation and intervention programs in this high-risk subgroup,” said Bao. This study proves the importance of prioritizing both BMI and WC to combat mortality risk correlated to cardiovascular disease and cancer in individuals with normal weight and central obesity.

Reference

Sun Y, Liu B, Snetselaar LG, et al. Association of normal-weight central obesity with all-cause and cause-specific mortality among postmenopausal women [published online July 24, 2019]. Jama Network Open. doi: 10.1001/jamanetworkopen.2019.7337.