Most DMARDs not linked with the risk of Parkinson's disease in people with rheumatoid arthritis

The autoimmune disorder rheumatoid arthritis has been associated with a lower risk of Parkinson's disease (PD) in previous studies, with antirheumatic drugs as one possible explanation.

However, most of the disease-modifying antirheumatic drugs (DMARDs) were not associated with the risk of PD in individuals with rheumatoid arthritis, a new register-based study from the University of Eastern Finland shows. An exception was the use of chloroquine or hydroxychloroquine which associated with a lower risk of PD. The findings were published online on January 21, 2022, in Neurology®, the medical journal of the American Academy of Neurology.

Risk factors for PD are still unclear. Rheumatoid arthritis has been linked to PD with conflicting findings, and both risk lowering and increasing findings have been reported. The medications used to treat rheumatoid arthritis could be one possible explanation for the potential lower risk of PD in individuals with rheumatoid arthritis but there are only few previous studies.

According to the newly published study, previous use of methotrexate, sulfasalazine, gold preparations or immunosuppressants at least three years before the PD diagnosis was not associated with the risk of PD in individuals with rheumatoid arthritis. However, users of chloroquine or hydroxychloroquine had a 26% lower relative risk of PD. Different comorbidities, such as cardiovascular diseases and diabetes, along with age, sex, and duration of rheumatoid arthritis, were controlled for in the study.

Chloroquine and the more commonly used hydroxychloroquine have various effects on the immune system. These medicines have been found to have antiparkinson potential in animal models of PD. According to researchers, the possible protective association of chloroquine and hydroxychloroquine should be further investigated.

This study was conducted as part of the FINPARK study, which covers 22,189 community-dwelling Finns with PD and a matched comparison cohort. The study was limited to persons who had been diagnosed with rheumatoid arthritis at least three years before PD.