Low Alzheimer's disease prevalence in rheumatoid arthritis patients is unrelated to ApoE genotype

Abstract Background : Population-based studies on patients with rheumatoid arthritis support a negative association between dementia due to Alzheimer's disease (DAT) and rheumatoid arthritis (RA). Several workers have suggested that inheritance of the apolipoprotein E (ApoE) e4 allele is a risk factor for developing DAT. In addition, earlier studies have suggested that ApoE e2 is under-represented in DAT, suggesting that it is a negative risk factor. Methods : To determine whether the distribution of the various isoforms of ApoE e2, in particular, could explain the low prevalence of DAT in the RA population, we carried out ApoE genotyping in 180 DAT patients, 75 RA patients, and 53 healthy controls. The ApoE e allele was determined by polymerase chain reaction. Results : There was no significant difference between the control group and the RA group in the distribution of the various alleles, in particular ApoE e2. The phenotype most frequently found in all three groups was Apo E3/E3. The ApoE3/E4 phenotype was much more frequent in the DAT group than in the RA group or in controls. The ApoE e4 allele was significantly more frequent in patients with Alzheimer's disease than in the other groups. Conclusions : Our results suggest that the presence of the Apo e2 allele is not what protects the RA patient from DAT.