Mixture effects of air pollutants on Parkinson’s disease in adults ages 40+ in the United States from 2002 to 2016

Recent studies have shown that air pollutants may have adverse effects on neurological disorders. However, few studies have investigated the long-term exposure of particle components in conjunction with NO₂ and ozone (O₃) to assess their individual and additive effects on Parkinson's disease. We utilized a weighted quantile sum regression to assess the joint effects of air pollutants, including 15 different fine particle components such as organic carbon (OC), elemental carbon (EC), copper (Cu), and zinc, along with NO₂ and O₃, on the risk of inpatient Parkinson's hospitalizations for adults ages 40 years and up. Inpatient records were collected from the State Inpatient Databases, which included hospitals from 11 US states, ranging in years from 2002 through 2016. We also included temperature from Daymet and variables from the US Census to control for socioeconomic status. All variables were aggregated to the annual level by ZIP code, including counts of admissions. We observed an increase of 21.2% (95% CI = 19.0%, 23.4%) in the number of Parkinson's inpatient hospitalizations each year associated with each decile increase of the 17 component pollutant mixture, and a 6.5% (95% CI = 0.0%, 12.2%) increase for each decile increase in the major pollutant mixture (EC, OC, NO₂, NO₃, SO₄, NH₄, and O₃). Our results suggest that O₃ and metals such as lead and Cu contribute the most to the association with Parkinson's hospitalizations and add to the growing body of literature on air pollution and neurological disorders.