The exposome and Parkinson’s disease: the role of air pollution and socioeconomic status—a systematic review

There is an unclear relationship between socioeconomic status (SES)—a social exposure—and PD risk, where those with a higher SES may be more at risk, or the inverse may be true. The risk of PD may not be directly related to SES, but exposures like outdoor air pollution may be involved, particularly as associations between SES and air pollution exposure, and between air pollution exposure and neurodegenerative outcomes have been noted. Scopus, PubMed, and PsycINFO were searched to identify studies analysing degree of exposure to chronic ambient outdoor air pollution and incidence of PD, or the association between individual measures of SES and degree of exposure to outdoor air pollution. 25,416 studies were screened, with 37 fitting inclusion criteria. Meta-analyses were conducted by air pollutant, with narrative syntheses when this was not possible. There was evidence of a positive association between exposure to NO 2 and PM 2.5 , and PD incidence. Higher and lower SES were associated with greater air pollution exposure, varying by location. The review had a low certainty of evidence, according to GRADE. Exposure to air pollution may be associated with greater risk of PD, and SES may play a role in the degree of air pollution exposure.