Association of Ambient Particulate Matter and Nitrogen Dioxide with Hospital Admissions for Parkinson's Disease: A Nationwide Case-Crossover Study in China.

Ambient particulate matter (PM) and nitrogen dioxide (NO) are both major air pollutants with potential neurotoxic effects. Beyond fine PM (PM), large population-based evidence on the associations of coarse PM (PM) and NO, especially co-exposure to high-concentration PM and NO, with hospital admissions for Parkinson's disease (PD) is crucial for PD risk management. In this time-stratified case-crossover study, patients with a principal discharge diagnosis coded of PD (G20) were identified. The associations of PM, PM and NO with increased admissions for PD were investigated based on hospital admissions data from the urban basic medical insurance schemes across 233 cities at or above the prefecture level in China during 2013-2017. A total of 293,357 hospital admissions were included in the study. An interquartile range increase in PM (34.5 μg/m), PM (20.2 μg/m) and NO (19.5 μg/m) at lag 01was associated with increases of 1.80% (95% confidence interval [CI], 0.71-2.90%), 2.93% (95% CI, 1.44-4.45%) and 4.67% (95% CI, 2.90-6.47%) in PD admissions, respectively. Only associations for PM and NO remained statistically significant after controlling for the other air pollutants and generalized propensity score. In comparison with low-concentration exposure (<30 percentile concentration), high-concentration exposures (≥60 percentile concentration) to PM and NO were both positively associated with increased PD admissions. Meanwhile, co-exposures to moderate and heavy exceedance of PM and NO were respectively associated with an increase of 4.61% (95% CI, 2.58-6.68%) and 9.72% (95% CI, 5.75-13.85%) in PD admissions, compared with within-standard co-exposure. This innovative exploration provided new epidemiological evidence that PM and NO may increase the risk of PD admissions independent of the other air pollutants, and co-exposure is likely associated with a more pronounced increase in PD admissions than separate exposure.