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Background: Uncontrolled studies have reported associations between later Parkinson's disease onset in women and a history of giving birth, with age at onset delayed by nearly 3 years per child. We tested this association in two independent data sets, but, as a control to test for nonbiological explanations, also included men with PD., Methods: We analyzed valid cases from the Parkinson's Progressive Markers Initiative incident sample (145 women, 276 men) and a prevalent sample surveyed by the New Zealand Brain Research Institute (210 women, 394 men)., Results: The association was present in both women and men in the Parkinson's Progressive Markers Initiative study, and absent in both in the New Zealand Brain Research Institute study. This is consistent with generational differences common to men and women, which confound with age at onset in incident-dominant samples., Conclusions: Despite being replicable in certain circumstances, associations between childbirth and later PD onset are an artifact of generational cohort differences. © 2020 International Parkinson and Movement Disorder Society., (© 2020 International Parkinson and Movement Disorder Society.)

Background: New Zealand is an ethnically diverse country with a unified national prescribing system. This provides a good framework to use drug-tracing methodology to establish the prevalence and incidence of Parkinson's disease across different ethnic groups. The objective of this study was to determine the prevalence and incidence of Parkinson's disease in the major ethnic groups in New Zealand., Methods: Information on Parkinson's disease-related medications was extracted from the national Pharmaceutical Collection of community-dispensed medications for the period January 1, 2005, to December 31, 2014. Diagnoses for a large subset of individuals were independently determined through national mortality and hospital admissions data sets. We used a Bayesian model, accommodating uncertainty and bias, to estimate the number of people with Parkinson's disease., Results: We found the highest rate of Parkinson's disease in the European ethnic group and the lowest rate in the indigenous Māori. The 2006-2013 age-standardized incidence (per 100,000 population per year) was European, 33; Asian, 28; Pasifika, 27; Māori, 20. The 2013 age-standardized prevalence (per 100,000 population) was European, 223; Asian, 174; Pasifika, 160; Māori, 114., Conclusions: There is a differential occurrence of Parkinson's disease across the major ethnic groups within the New Zealand population, with indigenous Māori showing the lowest incidence. Varying susceptibility profiles, gene-environment interactions, and inequalities in accessing health care may play a role in the variation in rates of Parkinson's disease in New Zealand. © 2018 International Parkinson and Movement Disorder Society., (© 2018 International Parkinson and Movement Disorder Society.)