APOLIPOPROTEIN-E GENOTYPING OF DIABETIC DEMENTIA PATIENTS - IS DIABETES RARE IN ALZHEIMERS-DISEASE

OBJECTIVES: To determine whether diabetes is rare in Alzheimer disease (AD) relative to other types of dementia and whether diabetics with d ementia have a low frequency of the Apolipoprotein-E E4 genotype. DESI GN: Observational survey study. SETTING: An Irvine, California, outpat ient dementia assessment center. PARTICIPANTS: A total of 123 patients with AD, 51 with vascular dementia, 57 with ''mixed'' vascular dement ia and AD, and 34 with ''other'' dementias (non-vascular non-AD). MEAS UREMENTS: Demographic data; histories and evidence of diabetes, hypert ension, heart disease, stroke; and Apolipoprotein-E genotype for 95 ca ses distributed across the groups. RESULTS: There were 15 diabetics in the sample (5.7%), all of whom had extensive vascular disease. Diabet es was rare in AD patients (0.8%) relative to vascular dementia (11.8% ), mixed vascular/AD dementia (8.8%), and ''other'' dementia patients (8.8%). In addition, the E4 allele of apolipoprotein-E, associated wit h high risk for AD, was frequent in the AD group (71.4%), but in the d iabetic group it was only as frequent as in the general population (38 .5%). In the diabetics with E4, 60% (3/5) had mixed dementia. CONCLUSI ONS: Diabetics with dementia rarely have AD except as a component of m ixed dementia. Apo-E genotyping showed only average E4 allele frequenc y in diabetics compared with the high E4 frequency found in AD patient s. However, mixed dementia in diabetics may be associated with the E4 allele, suggesting that close control of diabetes may be particularly important for those with E4 since they may be more likely than others to develop both diseases.