Antirheumatics not found to lower Parkinson’s risk

Disease-modifying antirheumatic drugs did not appear to be linked to a lower risk for Parkinson’s disease among individuals with rheumatoid arthritis, according to results of a nested case-control study published in Neurology.

“Rheumatoid arthritis has been linked to lower risk of Parkinson’s disease (PD), although some studies have also observed an increased risk of PD in people with rheumatoid arthritis, or no association between rheumatoid arthritis and PD,” Anne Paakinaho, MSc Pharm, of the School of Pharmacy at the University of Eastern Finland, and colleagues wrote.

“One suggested explanation for the protective association are medications used to treat rheumatoid arthritis,” they continued. “Disease-modifying anti-rheumatic drugs (DMARDs), such as methotrexate and sulfasalazine, inhibit the rheumatic inflammation and progression of structural joint damage, and they could modify the risk of PD by interfering with immune system dysfunction, which has been suggested to be present in PD.”

According to investigators, research is sparse regarding the relationship between DMARDs and risk for PD. To address this research gap, they analyzed data from the Finnish Parkinson’s disease cohort, which included 22,189 individuals with a clinically verified PD diagnosis. Paakinaho and colleagues examined cases with PD diagnosis between 1999 and 2015 and rheumatoid arthritis (RA) diagnosis more than 3 years before PD. They identified RA via the Finnish Care Register for Health Care and Special Reimbursement Register.

Further, researchers matched cases with up to seven control individuals based on age, sex, duration of RA and region and classified DMARDs into five groups and identified data on purchases prescriptions via the Prescription Register since 1995. They included 315 cases with PD and 1,571 matched controls; more than 60% were women. Controls and cases had a median duration of RA on matching date of 11.6 years and 12.6 years, respectively.

Results showed no association between use of DMARDs and risk for PD, with 3-year lag period applied between exposure and outcome; however, chloroquine/hydroxychloroquine appeared linked to decreased risk (adjusted OR = 0.74; 95% CI, 0.56-0.97). Researchers observed no association between other DMARDs, including sulfasalazine, methotrexate, gold preparations and immunosuppressants, and PD.

“The hypothesis that decreased risk of PD among rheumatoid arthritis patients could be explained by use of DMARDs was not confirmed in our study,” Paakinaho and colleagues wrote. “Further studies on newer DMARDs, especially on [biological] DMARDs such as [tumor necrosis factor-alpha] inhibitors and target specific DMARDs (JAK inhibitors), and assessment of dose-response relations between DMARDs and risk of PD are needed. The potential ability of chloroquine/hydroxychloroquine to modify the PD disease process should be studied further.”