The apolipoprotein E (Apo E) ɛ4 allele is known to be a risk factor for Alzheimer's disease (AD). However, there are debates about the relationship between Apo E ɛ4 frequency and subcortical vascular dementia (SVaD). We compared the frequency of the Apo E ɛ4 allele in AD and SVaD in Koreans.

The study was comprised of 400 subjects who visited the Dementia Clinic at Daegu Catholic University from July 2007 to December 2011. Neuropsychological tests, a brain MRI, and blood laboratory tests were performed on all subjects. Two hundred and ninety subjects were AD, 32 subjects were SVaD and 78 subjects were normal. The diagnosis for SVaD was based on the Diagnostic and Statistical Manual of Mental Disorders, Fourth Edition (DSM-IV) and Erkinjuntti criteria, and the diagnosis for AD was based on the DSM-IV and National Institute of Neurological and Communicative Disorders and Stroke and Alzheimer's disease and Related Disorders Association criteria. Apo E polymorphism was genotyped in all subjects.

The Apo E ɛ4 allele frequency was 17.4% in AD, 10.9% in SVaD and 8.3% in the normal group ( p =0.03). The odds ratio (OR) after age adjustment for AD conferred to the Apo E ɛ4 was 2.04 ( p =0.04). But, the OR for SVaD conferred to the Apo E ɛ4 allele was 1.34 ( p =0.62), indicating that the Apo E ɛ4 allele does not significantly confer the risk of SVaD.

Apo E ɛ4 is a reliable predictor of AD but has modest efficacy for predicting SVaD in Koreans.