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.