Apolipoprotein E genotypes and the risk of Parkinson disease.

We examined apolipoprotein E (ApoE) genotypes in relation to Parkinson's disease (PD) among 786 cases and 1537 controls, all non-Hispanic Caucasians. Odds ratios (ORs) and 95% confidence intervals (CIs) were derived from multivariate logistic regression models, adjusting for year of birth, sex, smoking status, daily caffeine intake, and family history of PD. Compared with participants with ApoE ε33, ε4 carriers (ε34/ε44) had significantly lower odds for having PD (OR, 0.75; 95% CI, 0.59-0.94; p = 0.01), whereas ε2 carriers (ε23/ε22) did not (OR, 0.95; 95% CI, 0.73-1.24; p = 0.71). Subgroup analyses showed similar results. In addition, we conducted a meta-analysis which confirmed our primary findings (ε34/ε44 vs. ε33: OR, 0.90; 95% CI, 0.81-0.99; p = 0.024 and ε23/ε22 vs. ε33: OR, 1.10; 95% CI, 0.97-1.23; p = 0.13). In PD patients, the prevalence of dementia appeared to be higher among ε4 carriers (compared with ε33: OR, 1.59; 95% CI, 0.98-2.58; p = 0.06), but lower among ε2 carriers (OR, 0.75; 95% CI, 0.40-1.42; p = 0.38), although neither test was statistically significant. Our study suggested that the ApoE ε4 allele may be associated with a lower PD risk among non-Hispanic Caucasians.