LAUSR

Living in rural regions increases the risk of Parkinson’s disease (PD) potentially as a result of agricultural pesticide exposure or other mechanisms. The global use of pesticides has markedly decreased in parallel with other relevant changes, such as increased access to piped clean water supply on premises instead of unimproved well water. We hypothesized that these changes may have decreased the rural-to-urban risk ratio of PD. We used annual national Finnish data of PD incidence from an 18-year period (1997-2014) using data from the Finnish National Prescription Register. All PD diagnoses were based on clinical examinations by certified neurologists. The 317 municipalities in Finland were categorized as rural or urban based on regional population size (urban 5 population> 30,000; rural 5<15,000) and distribution of labor force (production-based categorization; urban 5 proportion of workforce in the primary sector such as agriculture <5%, rural 5>5%; Statistics Finland, http://www. tilastokeskus.fi). Subjects were classified into 20 5-year age groups (ages 0-4, 5-9, etc., and 95 or more years). Data management and statistical analyses were performed using the SAS System for Windows, version 9.4 (SAS Institute, Cary, North Carolina). We used PROC STDRATE to obtain rural/urban-specific ageand gender-standardized annual incidence rates (IR) of PD and their 95% confidence