WASHINGTON – Type 2 diabetes did not increase the risk of onset or progression of Alzheimer's disease in older adults, according to results from a study of more than 700 individuals presented in a poster at the annual meeting of the American Geriatrics Society.
The prevalences of Alzheimer's disease (AD) and type 2 diabetes are rising, and data from previous studies suggest an association between the two conditions.
In this prospective study, Youngjee Choi of the Alzheimer's Disease Research Center and a medical student at Washington University in St. Louis, and colleagues examined the frequency of type 2 diabetes in 506 adults (196 men and 310 women) with dementia and 318 adults (127 men and 191 women) without dementia.
The study participants, who were enrolled in a longitudinal study of aging and dementia, had an average age of 77 years. The mental status of the participants was determined using the Clinical Dementia Rating, which is sensitive to individual cognitive decline. The study excluded individuals with diabetes who used insulin.
Significantly more of the participants with dementia had type 2 diabetes at baseline than did the nondemented participants (10.7% vs. 5.7%).
But a Cox regression analysis showed no association between type 2 diabetes and the onset or progression of AD during a 12-year follow-up period, although AD and type 2 diabetes were significantly associated at baseline in this sample.
Independent of type 2 diabetes, dementia progression was significantly higher among the participants who were demented at baseline, compared with those who were not. Older age and the presence of the APOE ?4 allele significantly increased the risk of AD onset in nondemented individuals. Older age, the presence of the APOE ?4 allele, and being female and having less education were significantly associated with dementia progression in those who met criteria for AD at baseline.
The study did not use a community-based sample, which may have caused selection bias, and the duration of disease and level of glucose control for the participants with type 2 diabetes were unknown, the researchers noted.
The study was supported in part by grants from the National Institutes of Health and the Summer Training on Aging Research Topics-Mental Health program. None of the researchers disclosed any financial conflicts.