Diabetes is Not Associated with Alzheimer's Disease Neuropathology

Abstract

Background: Previous evidence linking diabetes to Alzheimer's disease (AD) neuropathology is mixed and scant data are available from low-and middle-income countries. Objective: To investigate the association between diabetes and AD neuropathology in a large autopsy study of older Brazilian adults. Methods: In this cross-sectional study, diabetes was defined by diagnosis during life or use of antidiabetic medication. A standardized neuropathological examination was performed using immunohistochemistry. The associations of diabetes with Consortium to Establish and Registry for Alzheimer Disease (CERAD) scores for neuritic plaques and Braak-Braak (BB) scores for neurofibrillary tangles were investigated using multivariable ordinal logistic regression. We investigated effect modification of education, race, and APOE on these associations. Results: Among 1,037 subjects (mean age = 74.4 +/- 11.5 y; mean education = 4.0 +/- 3.7 y; 48% male, 61% White), diabetes was present in 279 subjects. Diabetes was not associated with BB (OR = 1.12, 95% CI = 0.81-1.54, p = 0.48) or with CERAD (OR = 0.97, 95% CI = 0.68-1.38, p = 0.86) scores on analyses adjusted for sociodemographic and clinical variables. We observed effect modification by the APOE allele epsilon 4 on the association between diabetes mellitus and BB scores. Conclusion: No evidence of an association between diabetes and AD neuropathology was found in a large sample of Brazilians; however, certain subgroups, such as APOE allele epsilon 4 carriers, had higher odds of accumulation of neurofibrillary tangles.