Researchers have discovered a link between specific cognitive deficits and the inflammatory activity associated with rheumatoid arthritis. These deficits include reductions in working memory, inhibition, focus, as well as memory, abstract thinking, and visuospatial abilities.
While rheumatoid arthritis-related inflammation has been associated with various systemic effects, including on the brain, the specific cognitive domains affected remain unclear. To investigate, researchers compared the cognitive function of 70 adults with rheumatoid arthritis (80% women, average age 56) receiving care at a hospital.
Almost 75% of the patients (49 out of 72%) exhibited persistent moderate to high levels of systemic inflammatory activity from their disease, as indicated by protein levels and joint inflammation, despite standard drug treatment. On an average, these patients had been living with the disease for 10.5 years. Between June 2022 and June 2023, all 140 participants underwent thorough neurological and psychological evaluations, including various validated cognitive tests, as well as assessments of mood and quality of life.
The cognitive abilities assessed included processing and organising visuospatial information, naming, attention, language, abstract thinking, delayed recall, orientation, and executive functions such as working memory, concentration, and inhibition. Cognitive impairment was identified as a Montreal Cognitive Assessment (MoCA) score below 26 out of a possible 30.
Data was gathered on various influential risk factors, including age, sex, smoking, alcohol consumption, high blood pressure, obesity, blood lipid levels, diabetes, and a history of heart disease or stroke. Generally, individuals with cognitive impairment were older, had lower educational levels, and more coexisting conditions such as obesity, elevated blood lipid levels, and high blood pressure compared to those with intact cognition. Patients with rheumatoid arthritis had lower average scores on the Montreal Cognitive Assessment (ranging from 23 to 25) and poorer executive function scores compared to the volunteers. Cognitive impairment was observed in 60% of the patients, versus 40% of the volunteers. Additionally, patients with rheumatoid arthritis exhibited significantly higher levels of anxiety and depression and reported lower quality of life compared to the volunteers.
Patients with cognitive impairment experienced more severe and ongoing inflammatory activity compared to those who preserved their cognitive function. They were also more prone to symptoms of depression and had reduced physical capacity. The factors linked to the highest risk of cognitive impairment among these patients were obesity (nearly six times the risk) and persistent inflammatory activity throughout the disease (approximately double the risk). Additionally, as seen in the general population, older age and lower educational attainment were also associated with increased risk.
To explain their findings, the researchers refer to previous suggestions that chronic inflammation, autoimmune processes, and ongoing pain and fatigue linked to rheumatoid arthritis may contribute to the decline in cognitive function. Since this is an observational study, it cannot establish definitive causal relationships. The researchers also recognise several limitations, such as the absence of imaging tests to identify vascular damage related to cognitive impairment.
However, they conclude: “These findings support the hypothesis that rheumatoid arthritis is a chronic systemic inflammatory disease impacting various systems, including neural tissue. The results emphasise the need for earlier and more rigorous management of arthritis activity and the development of new therapeutic strategies targeting associated factors to reduce the risk of cognitive impairment in patients with rheumatoid arthritis.”