Abstract and Introduction
Abstract
Objectives: To assess the relationship between body mass index (BMI) and waist–hip ratio (WHR) and the clinical end points of cognitive impairment and probable dementia in a cohort of older women enrolled in the Women's Health Initiative Memory Study (WHIMS).
Design: Prospective, randomized clinical trial of hormone therapies with annual cognitive assessments and anthropometrics.
Setting: Fourteen U.S. clinical sites of the WHIMS.
Participants: Seven thousand one hundred sixty-three postmenopausal women aged 65 to 80 without dementia.
Measurements: Annual cognitive assessments, average follow-up of 4.4 years, including classification of incident cognitive impairment and probable dementia. Height, weight, waist, and hip measurements were assessed at baseline, and a waist–hip ratio (WHR) of 0.8 or greater was used as a marker of central adiposity.
Results: There were statistically significant interactions between BMI and WHR and incident cognitive impairment and probable dementia with and without adjustment for a panel of cognitive risk factors. Women with a WHR of 0.80 or greater with a BMI of 20.0 to 24.9 kg/m had a greater risk of cognitive impairment and probable dementia than more-obese women or women with a WHR less than 0.80, although women with a WHR less than 0.80 and a BMI of 20.0 to 24.9 kg/m had poorer scores on cognitive assessments.
Conclusion: WHR affects the relationship between BMI and risk of cognitive impairment and probable dementia in older women. Underweight women (BMI<20.0 kg/m) with a WHR less than 0.80 had a greater risk than those with higher BMIs. In normal-weight to obese women (20.0–29.9 kg/m), central adiposity (WHR≥0.80) is associated with greater risk of cognitive impairment and probable dementia than in women with higher BMI. These data suggest that central adiposity as a risk factor for cognitive impairment and probable dementia in normal-weight women.
Introduction
There is increasing interest in the effects of modifiable risk factors, such as obesity, on cognitive impairment and dementia in older adults. Midlife obesity, and more recently central obesity, is associated with a long-term risk of dementia, although this relationship was not seen in a recent study of overweight and obesity in old age. Especially in older women, overweight and moderate obesity have not consistently been shown to be associated with poorer cognitive profiles. Critical to this may be the location of body fat—whether excess fat is distributed centrally or peripherally. The present study used data from women enrolled in the Women's Health Initiative (WHI) Memory Study (WHIMS), a large cohort of women, aged 65 to 80 at baseline, to describe relationships between body mass index (BMI) and central adiposity, as characterized by waist–hip ratio (WHR), and risk of cognitive impairment and probable dementia.