Parkinson's disease prevalence and the association with rurality and agricultural determinants

Parkinson's disease prevalence has been associated with rurality and pesticide use in studies throughout the world. Here, Parkinson's disease (PD) medication usage was used to estimate prevalence in 79 urban and rural localities in Victoria, Australia (5.3 million people).

An ecological study design was used to determine whether PD medication usage, as a reporter of PD diagnosis, differed between 79 regions in Victoria, and whether variance in PD prevalence was associated with population demographics using multiple regression. Cluster formation probability was calculated using Monte Carlo modelling. The association between agricultural production and PD prevalence was conducted with Bonferroni-adjusted Mann-Whitney-U tests.

PD prevalence in Victoria was estimated to be 0.85%, which was greater in rural (1.02%) compared to urban (0.80%) locations; a difference that was abolished when corrected for demographic variables. Four of the highest prevalent regions (regardless of covariate adjustment) were clustered in northwest Victoria; a formation that was unlikely to be due to chance (P = 0.00095). These regions had increased production of pulse crops.

PD prevalence was not associated with rurality, but associated with areas of pulse production. Pulses are plants of the fabaceae family, where many of these species secrete the PD toxin, rotenone, as a natural pesticide, which may underlie increased risk. This study is limited by the data collection method, where people who do not take PD medication for their disease, or take PD-associated medication for other diseases, may impact the estimated prevalence.