APOE and the risk of PD with or without dementia in a population-based study

Objective: To study the association between APOE genotype and PD with or wi thout dementia. Methods: The study formed part of the Rotterdam Study, a pr ospective, population-based cohort study on the frequency, etiology, and pr ognosis of chronic diseases. The cohort examined for PD consisted of 6969 i ndependently living or institutionalized inhabitants Li om a suburb of Rott erdam, the Netherlands, aged 55 years or older. All participants were scree ned at baseline (1990 to 1993) and at follow-up (1993 to 1994) for symptoms of parkinsonism by study physicians; screen positives received a diagnosti c workup by a neurologist. Results: APOE genotyping was available for 107 P D patients (26 with and 81 without dementia) and 4805 non-PD control subjec ts. The presence of at least one is an element of 2 allele significantly in creased the risk of PD (OR = 1.7; 95% CI, 1.0 to 2.8). When we looked separ ately far demented and nondemented PD patients as compared with nonparkinso nian controls, APOE did not appear to be associated with PD without dementi a, but both the is an element of 2 and the is an element of 4 allele increa sed the risk of PD with dementia (OR = 5.6; 95% CI, 2.0 to 15.2 and OR = 3. 6; 95% CI, 1.3 to 9.9). The risk of dementia for is an element of 4 allele carriers was not significantly different for persons with or without PD. Ho wever, the is an element of 2 allele strongly increased the risk of dementi a in patients with PD (interaction p < 0.007). Conclusions: In the elderly the APOE-is an element of 2 allele increases the risk of PD and, in particu lar, the risk of PD with dementia.