Association of Rheumatoid Arthritis With Progression of Cognitive Impairment and Risk of Mortality in People With Dementia.

Abstract

Rheumatoid arthritis (RA) has been linked to an increased risk of dementia, yet little is known about how RA affects the progression of cognitive impairment and the risk of mortality in people with dementia. We aimed to investigate whether RA is linked to an accelerated cognitive decline and a higher risk of all-cause mortality in patients with dementia. We conducted a propensity score-matched register-based cohort study based on the Swedish Registry for Cognitive/Dementia Disorders-SveDem. Patients diagnosed with dementia and registered in SveDem between May 1, 2007, and October 16, 2018, were included. The main outcome for the study was cognitive decline, measured by Mini-Mental State Examination (MMSE) score changes over years. The secondary outcome was all-cause death. We used mixed-effects models to examine the association between RA and cognitive decline, and Cox proportional hazards models to investigate the risk of all-cause mortality. We also conducted subgroup analyses to explore the potential effects of sociodemographic, baseline MMSE, comorbidities, and the use of dementia medications on the association between RA and outcomes. We included 1,685 dementia patients with RA (mean [SD] age, 79.9 [6.7] years; 73.4% were women) and 5,055 dementia patients with non-RA (80.1 [7.5] years; 73.1% were women). The median follow-up was 2.9 years (interquartile range, 1.5-4.6 years) for non-RA and 2.6 years (interquartile range, 1.4-4.2 years) for RA. In total, 111,266 MMSE measurements were available for analysis. Compared with non-RA patients, patients with RA presented faster cognitive decline (β = -0.24 points/y; 95% CI -0.38 to -0.10) and an increased risk of death (hazard ratio 1.15; 95% CI 1.06-1.24). In subgroup analysis, significant interactions were observed between RA and baseline MMSE scores as well as living conditions regarding cognitive decline (<i>p</i> for interaction <0.05). We identified a worse cognitive function and an increased mortality risk in dementia patients with RA compared with non-RA. However, we lacked information on the duration of RA before the onset of dementia and on disease activity, which could influence our findings. Further studies are needed to validate these results in comparable populations.