The use of disease-modifying antirheumatic drugs (DMARDs) was not associated with a lower risk for Parkinson disease (PD) among individuals with rheumatoid arthritis (RA), according to a study published in Neurology.

RA results from the immune system attacking its own tissue, such as the joints, which can cause inflammation and pain in areas such as the hands and feet. Previous epidemiological research has suggested a link between RA and PD. Researchers hypothesize DMARDs—intended to inhibit inflammation—may interfere with immune responses seen in patients with PD. However, other research has reported an increased risk for PD in individuals with RA, or has found no link between the two conditions.

The objective of the current study was to evaluate the link between DMARDs and the risk for PD in patients with RA.


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The nationwide case-control study consisted of 315 individuals with PD and 1571 control individuals, recruited from the Finnish PD (FINPARK) cohort (N=22,189), which included individuals who received reimbursement for PD drugs between 1996 and 2015 as noted in the Special Reimbursement Register. Study participants had a PD diagnosis between 1999 and 2015 and a RA diagnosis more than 3 years before their initial PD diagnosis. ​​Mean age was 73.1 years, and over 60% of the study participants were women.

The Finnish Care Register for Health Care and Special Reimbursement Register were used to identify RA. Each person with PD and RA was matched with up to 7 control individuals according to region, duration of RA, sex, and age. The Prescription Register was used to identify data on purchased prescriptions. DMARDs were stratified into 5 classes, and conditional logistic regression was used to examine associations with adjustments for confounders.

The median duration of RA was 12.6 years among those with PD vs 11.6 years among control individuals on the index date. No association was identified between DMARDs, including sulfasalazine, methotrexate, gold preparations, and immunosuppresants, or corticosteroid use and risk for PD, with the exception of chloroquine/hydroxychloroquine, which correlated with reduced risk for PD (adjusted odds ratio 0.74; 95% CI, 0.56-0.97).

Study limitations included limited ability to detect weak associations, as well as a lack of data on RA severity.

The researchers concluded that “the hypothesis that decreased risk [for] PD among rheumatoid arthritis patients could be explained by use of DMARDs was not confirmed in our study.” They also noted the need for “further studies on newer DMARDs, especially on bDMARDs such as TNF-α inhibitors and target specific DMARDs (JAK inhibitors), and assessment of dose-response relations between DMARDs and risk [for] PD.”

Reference

Paakinaho A, Koponen M, Tiihonen M, Kauppi M, Hartikainen S, Tolppanen AM. Disease-modifying antirheumatic drugs and risk of Parkinson disease: nested case-control study of people with rheumatoid arthritis. Published online January 21, 2022. Neurology. doi:10.1212/WNL.0000000000013303