Risk of dementia associated with body mass index, changes in body weight and waist circumference in older people with type 2 diabetes: The Edinburgh Type 2 Diabetes Study.

Abstract

To determine the relationship of dementia with preceding body mass index (BMI), changes in body weight and waist circumference in older people with type 2 diabetes. In the Edinburgh Type 2 Diabetes Study (1064 men and women with type 2 diabetes, aged 60-75), body weight, waist circumference and BMI were measured at baseline and after 4 years in a subgroup (n= 821). Percentage body weight and waist circumference change over 4 years were calculated. Data on incident dementia was recorded during a median follow-up time of 10.84 years. Survival models considering a range of co-variables and/or death as a competing risk were used to estimate the risks of dementia associated with each weight-related variable. A total of 105 incident dementia events were recorded. When compared with people in the lowest BMI group (<25 kg/m2 ), risk of dementia was lower in intermediate BMI groups (25-29.9kg/m2 , HR 0.44, p= 0.002; 30-34.9kg/m2 , HR 0.41, p= 0.001) and the highest BMI group (≧35 kg/m2 , HR 0.35, p= 0.001). In the weight change subgroup, 78 incident dementia events were recorded between years 4 and 10. Body weight loss over 5% (compared with ≦5%) was associated with higher incidence of dementia (HR 2.06, p= 0.010). The association between waist circumference change and dementia was not significant. Both a lower BMI and weight loss over a period of years are indicative of increased dementia risk for older people with type 2 diabetes, while waist circumference changes may be less informative.