Association between use of ß2-adrenergic receptor agonists and incidence of Parkinson’s disease: Retrospective cohort analysis

INTRODUCTION: Previous observational studies assessing β2-agonist/-antagonist use on PD risk have yielded conflicting results. We evaluated the relationship between β2-agonist use and the incidence of Parkinson’s disease in patients with chronic lung disease. METHODS: We performed a retrospective cohort analysis on a 20% random sample abstracted from a traditional (fee-for-service) Medicare program in the United States. Inclusion criteria were individuals over 65 years old diagnosed with asthma, COPD, and/or bronchiectasis who were enrolled in a prescription drug (standalone Part D) plan over 2007–2010 and alive through 2014. The main outcome measure was a diagnosis of Parkinson’s disease over the period 2011–2014, in relation to the number of 30-day-equivalent drug claims over 2007–2010. Logistic regression analysis was performed on a sample including 236,201 Medicare beneficiaries. RESULTS: The sample was 68% female, 80% white, and on average 77 years old as of 2010. Compared to non-users, β2-agonist users were more likely to be younger (76.3y versus 78.0y), smokers (40.4% versus 31.1%) and asthmatic (62.4% versus 28.3%). The odds ratio for a β2-agonist claim on PD development was 0.986 (95% CI 0.977–0.995) after adjusting for demographics, smoking history, respiratory exacerbations, comorbidities, and other drug use. Risk reductions were larger for males than females (0.974 versus 0.994, P = 0.032), and for individuals with COPD compared to those with asthma (0.968 versus 0.998, P = 0.049). Reverse causality was addressed with a Cox analysis that allowed β2-agonist use to vary from medication initiation to disease onset. By the end of the follow-up period, β2-agonist use was shown to be associated with a true protective effect against PD onset. DISCUSSION: β2-agonist use is associated with decreased risk of PD incidence. Further investigation, possibly including clinical trials, is warranted to strengthen the evidence base supporting clinical decision-makers looking to repurpose pharmaceuticals to prevent neurodegenerative disease onset.