β2-Adrenoceptor Agonists in Asthma or Chronic Obstructive Pulmonary Disease and Risk of Parkinson's Disease: Nested Case-Control Study.

Higher levels of exposure to β2AR agonists were not consistently associated with a reduced risk of PD. The inverse association in the highest category of average annual exposure to long-acting β2AR agonists may be explained by unmeasured confounding, such as disease severity or smoking.