Increased risk of Parkinson's disease in parents and siblings of patients

We studied the incidence of Parkinson's disease in 586 first‐degree relatives (parents and siblings) of 114 randomly ascertained white patients with idiopathic Parkinson's disease and in 522 first‐degree relatives of 114 age‐matched unrelated white control subjects. Sixteen percent of patients had a family history as compared to 4% of control subjects (p < 0.01). The age‐specific cumulative incidence was higher in the first‐degree relatives of patients than in the first‐degree relatives of control subjects (p = 0.007). The age‐adjusted odds ratio was 3.5 (95% confidence interval: 1.3–9.4; p = 0.014). These results suggest that genes contribute to the etiology of Parkinson's disease.