Interaction Between Body Mass Index and Central Adiposity and Risk of Incident Cognitive Impairment and Dementia: Results from the Women's Health Initiative Memory Study

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/m2 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/m2 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/m2) 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/m2), 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.