Background and Purpose: The effect of serum rheumatoid factor (RF) on post-stroke cognitive impairment remains unknown. We aimed to investigate the association of serum RF in the acute phase with cognitive impairment at 3 months after ischemic stroke onset.
Methods: Our study was based on a random sample from the China Antihypertensive Trial in Acute Ischemic Stroke (CATIS), a total of 582 patients from 7 of 26 participating sites of the trial with serum RF levels were included in this analysis. Cognitive impairment was defined as a score of <27 for Mini-Mental State Examination (MMSE) or <25 for Montreal Cognitive Assessment (MoCA). 
Results: According to MMSE score, the multivariate adjusted odds ratio and 95% confidence interval (CI) of cognitive impairment for the highest tertile of serum RF was 1.79 (1.08-2.99) compared with the lowest tertile. Each standard deviation increase of log-transformed RF was associated with 33% (95% CI: 7–66%) increased risk of cognitive impairment, and a linear association between serum RF and risk of post-stroke cognitive impairment was observed (P for linearity<0.01). Adding log-transformed RF to a model containing conventional risk factors improved the predictive power for post-stroke cognitive impairment (net reclassification improvement: 26.21%, P<0.01; integrated discrimination index: 1.24%, P=0.02). Similar significant findings were observed when cognitive function was defined by MoCA score.
Conclusions: Elevated serum RF levels in the acute phase were independently associated with 3-month cognitive impairment among ischemic stroke patients. Further studies are needed to replicate our findings and to clarify the potential mechanisms.

Association of Serum rheumatoid factor levels with cognitive impairment after acute ischemic stroke