PATIENTS with rheumatoid arthritis have a 1.74-fold increased risk for developing Parkinson’s disease, according to a novel study led by Jihun Kang, Kosin University College of Medicine, Busan, South Korea, and colleagues.
According to Kang, “the pathogenesis of Parkinson’s disease has been largely elusive, except for a small fraction of cases caused by rare genetic variants.” Kang went on to say: “Multiple lines of clinical and experimental evidence have suggested that autoimmunity is involved in the activation of microglia and monocytes that play a central role in the initiation and amplification of brain inflammation.”
Kang and colleagues investigated the potential connection between rheumatoid arthritis and Parkinson’s disease by analysing data from the Korean National Health Service. Patients who were diagnosed with rheumatoid arthritis between 2010–2017 were identified by prescriptions for any disease-modifying anti-rheumatic drug and diagnostic code.
Individuals aged 40 years and younger were excluded from the data, as were those who were registered in the Rare and Intractable Disease (RID) programme, had been diagnosed with Parkinson’s disease within 1 year of enrolment, presented with a disease that was not rheumatic in nature, had a history of Parkinson’s disease, had missing data, or could not be matched in the control group.
A total of 328,080 patients were included in the final analysis, of whom 1,093 were diagnosed with Parkinson’s disease. Patients with rheumatoid arthritis had a 1.74-fold increased risk of developing Parkinson’s disease compared with the control group (95% confidence interval [CI]: 1.52–1.99), while patients with seropositive rheumatoid arthritis were more likely to develop Parkinson’s disease (adjusted hazard ratio: 1.95; 95% CI: 1.68–2.26). However, this was not the case with patients with seronegative rheumatoid arthritis (adjusted hazard ratio: 1.2; 95% CI: 0.91–1.57).
Kang and colleagues noted that “the study findings suggest that physicians who care for patients with rheumatoid arthritis should be aware of the elevated risk of Parkinson’s disease, and prompt referral to a neurologist should be considered at onset of early motor symptoms of Parkinson’s disease in patients with rheumatoid arthritis without synovitis.”
