Maternal effect on Parkinson's disease.

First-degree relatives of patients with Parkinson's disease (PD) are at higher risk for PD development than first-degree relatives of control subjects, but clinical twin studies have failed to demonstrate a genetic basis in PD. It is hypothesized that maternal exposure to certain environmental factors could lead to pathological changes in the ovum that predispose to the development of PD in the child. In this study of 299 patients and 295 controls, the age at onset of PD was found to correlate negatively with maternal age at birth of patient but not with paternal age. Mothers and fathers of patients with PD had an increased risk of PD as compared with parents of control subjects. These results suggest a maternal effect on PD that could be primarily environmental in nature.