Left-handedness was associated with a 62% increased risk of PD in women but not in men.

Mov Disord. 2010 Aug 15;25(11):1560-7.

Prenatal and early life factors and risk of Parkinson's disease.
Gardener H, Gao X, Chen H, Schwarzschild MA, Spiegelman D, Ascherio A.

Department of Epidemiology, Harvard School of Public Health, Boston, Massachusetts, USA.

Abstract
Few studies have investigated the relation between early life factors and risk of Parkinson's disease (PD), although a potential role of exposures during pregnancy and childhood has been hypothesized. The study population comprised participants in two prospective cohorts: the Nurses' Health Study (121,701 female nurses followed up from 1976-2002) and the Health Professionals Follow-up Study (51,529 male health professionals followed up from 1986-2002). PD risk was examined in relation to season of birth, birthweight, parental age at birth, preterm birth, multiple birth, ever having been breast-fed, and handedness. We identified 659 incident PD cases. No significant relation with PD was observed for birthweight, paternal age, preterm birth, multiple birth, and having been breast-fed. A modest nonsignificant association was suggested for season of birth (30% higher risk of PD associated with spring versus winter birth) and for older maternal age at birth (75% increased risk among those with mothers aged 30 years and older versus younger than 20 years). Left-handedness was associated with a 62% increased risk of PD in women but not in men. Further investigation of the relation between prenatal, perinatal, or neonatal factors and PD in other study populations is suggested. (c) 2010 Movement Disorder Society.