Although researchers found no substantial changes in body mass index (BMI) among postmenopausal women, the metric was a risk factor for diabetes and cardiovascular disease (CVD).
An analysis of data from the Women’s Health Initiative (WHI) showed a strong association between high body mass index (BMI) and diabetes and cardiovascular disease (CVD), highlighting the importance of additional longitudinal research on adverse health effects of BMI in older women. Findings were published in Annals of Epidemiology.
Older adults are the fastest-growing segment of the US population, and life expectancy among women is 5 years longer than that of men on average. In addition, due to the concomitant rise in obesity in the last few decades, “there are an increasing number of older women with obesity in the population,” authors wrote.
Because limited research exists on changing weight or hormones in postmenopausal women, these investigators sought to address this knowledge gap by analyzing data from postmenopausal women aged 50 to 79 years enrolled in the WHI between 1993 and 1998.
The WHI took place at 40 clinical centers across the United States and examined the effects of hormone therapy use, dietary modification, and use of calcium/vitamin D supplements. Comprehensive medical questionnaires were completed on an annual basis; any patient with baseline diabetes, CVD, or cancer was excluded from the current analysis.
A total of 54,073 women were assessed. Researchers “used a growth mixture modeling (GMM) approach to divide the study population into subgroups (unobserved ‘latent classes’) that each have distinct longitudinal patterns of BMI,” the authors explained.
It is believed that individuals in different latent subgroups will have distinct trajectories and those in the same subgroups will have similar longitudinal patterns of BMI change. The BMI trajectories were then examined based on their relationship with incident diabetes and cardiovascular outcomes, with the lowest BMI trajectory serving as the reference group.
Five trajectories were found: low (n = 12,417), moderate (n = 18,539), moderate-high (n = 13,635), high (n = 7406), and very high (n = 2076) with respective mean BMI values of 21.8 kg/m2, 25.6 kg/m2, 29.8 kg/m2, 34.7 kg/m2, and 43.3 kg/m2.
In individuals in the low trajectory subgroup, risk of diabetes was measured at 7.9% (95% CI, 7.4%-8.4%). For those in the very high trajectory, diabetes risk was 34.3% (95% CI, 31.8%-36.8%).
Overall, BMI trajectory groups were stable over time, regardless of time since menopause or hormonal therapy use, and a positive association was seen between risk of diabetes, CABG and PCI, and total CVD and increasing BMI.
“Consistent with prior WHI research, time since menopause had an important impact on effect estimates: Women who were 0-10 years from menopause were at greater risk of adverse outcomes compared to those more than 10 years since menopause,” the authors added.
Although they considered the lack of substantial change in BMI “unexpected,” the researchers hypothesized this could be due to the change in female body composition in the postmenopausal period, when body fat shifts to a more centralized distribution pattern. In addition, if a woman loses height as she ages, it will decrease the denominator of her BMI, but this may also be attenuated by a decrease in bone mineral density over time.
“These plausible age-related changes in body composition could result in a consistent BMI value over time, despite changes in body composition,” the researchers wrote. “This is a potential limitation of using BMI as an anthropometric measure in older adults and should be considered when interpreting the results of the present analysis.”
Despite the lack of change in BMI over time, the metric does continue to serve as a risk factor for chronic diseases in the postmenopausal period.
“We were surprised to find minimal evidence of BMI change over time as it is often stated that, in general, women gain weight after menopause,” the authors concluded. “Additional research on longitudinal patterns of BMI in older adults is necessary to assess whether these relationships generalize to other populations.”
Banack HR, Chang J, Stefanik ML, Arnold M, Anton-Culver H, Jiang L. Relationship between BMI trajectories and cardiometabolic outcomes in postmenopausal women–a growth mixture modelling approach. Ann Epidemiol. Published online April 22, 2022.