Familial aggregation of Parkinson's disease - A population-based case-control study in Europe

Objective: To investigate the familial aggregation of PD in a large collabo rative population-based case-control study. Background: Most previous case- control studies of the familial aggregation of PD have been hospital- or cl inic-based. Methods: We included 219 prevalent cases ascertained in three E uropean populations (centers), using a two-phase design consisting of scree ning and examination by a neurologist. Each case was matched by age, sex, a nd center to three controls drawn from the same populations (n = 657). Pres ence of PD among first-degree relatives (parents and siblings) was determin ed using the family history approach for 175 cases and 481: controls. Resul ts: Overall, a positive family history (at least one parent or sibling affe cted by PD) was reported in 10.3% df patients and 3.5% of controls (odds ra tio [OR] = 3.2; 95% confidence interval [CI] = 1.6 to 6.6). A similar assoc iation was observed when analyses were restricted to nondemented patients a nd controls (OR = 3.9; 95% CI = 1.7 to 8.7) or to newly diagnosed patients (OR = 3.3; 95% CI = 0.9 to 11.9). We found a significant trend of increasin g risk with: increasing number of-affected relatives Cp = 0.003). Analyses stratified by age showed a stronger association for younger PD patients (OR = 7.6; 95% CI = 1.5 to 38.9) than for older patients (OR = 2.5; 95% CI = 1 .1 to 5.7). Conclusion: In this large sample of prevalent PD patients and p opulation-matched;controls, PD significantly aggregates in families, with t he strength of the association being age-dependent. Therefore, familial fac tors, which can be genetic, environmental, Or both, play a role in PD.