Prevalence of Alzheimer's disease with diabetes in the Japanese population

Background:  The aim of the present study was to estimate the prevalence of impaired cognitive function and Alzheimer's disease (AD) in diabetic subjects from Japan.
Methods:  In the present study, 386 Japanese diabetic subjects aged more than 50 years were initially screened with the 'brief screening test' for AD, and were diagnosed with AD and vascular dementia (VaD) according to the criteria of the NINCDS-ADRDA and the NINDS-AIREN. We compared the prevalence of dementia in diabetic patients with that in ordinary subjects, and analyzed the association of the status of diabetes with dementia including AD and VaD.
Results:  Forty-six (11.9%) patients were diagnosed with dementia, including 13 (3.4%) patients with AD and nine (2.3%) patients with VaD. Of the 221 subjects aged more than 65 years, 39 (17.6%) patients had dementia, including 13 (5.9%) patients with AD and eight (3.6%) patients with VaD. Compared with ordinary subjects, the prevalence of dementia in the present study was more frequent than the prevalence of dementia for the general population in almost each age group examined. There was also a greater prevalence of AD and VaD in subjects aged over 65 years in the present study. In the present study, AD subjects had significantly higher levels of fasting plasma glucose (FPG; 247.5 ± 116.3 mg/dL; P  < 0.05) and glycosylated hemoglobin (HbA1c; 8.8 ± 1.9%; P  < 0.01) compared with non-demented subjects. In AD patients, the odds ratios of FPG and HbA1c were also significantly higher (1.02 and 2.07, respectively; both P  < 0.01).
Conclusion:  The present study shows that diabetes can be associated with impaired cognitive function, particularly AD, in Japanese subjects.