By contrast, the only study directly adjusting for smoking (not just chronic obstructive pulmonary disease [COPD]) found a significant association between β2 agonists and reduced PD risk,48 and a follow-up study from Norway reports that after the exclusion of patients with COPD, corticosteroids and anticholinergics were no longer inversely associated with PD risk, whereas β2AR agonists remained associated.46 Here, ADRB2 is linked to Parkinson disease.