Among patients with rheumatoid arthritis (RA), those with lower socioeconomic status (SES) have worse functional status and faster declines in functioning over time, according to study findings published in JAMA Network Open.

Researchers analyzed data from the American College of Rheumatology’s national Rheumatology Informatics System for Effectiveness (RISE) registry. Eligible patients were aged 18 years or older, had at least 2 rheumatology visits that were at least 30 days apart, and had at least 1 functional status measure documented from January 1, 2016, to December 31, 2018.

The Area Deprivation Index (ADI), a zip code–based indicator of neighborhood socioeconomic disadvantage that incorporates income, education, employment, and housing quality, was used as a proxy for patients’ SES.


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A total of 83,965 patients with RA from 109 practices were included in the cross-sectional analysis—mean (SD) age, 63.4 (13.7) years; 66,649 (77%) women; and 60,037 (72%) non-Hispanic White. Participants had a median (interquartile range [IQR]) ADI score of 43 (23-66). ADI scores of 1 to 18 and 72 to 100 corresponded with the first and fifth ADI quintiles, respectively.

The Multidimensional Health Assessment Questionnaire (MDHAQ) was the most frequently reported functional status measure (56,928 patients [68%]) in the cross-sectional cohort, followed by the Health Assessment Questionnaire Disability index (HAQ) (20,488 [24%]) and Health Assessment Questionnaire–II (HAQ-II) (6549 [8%]).

Participants’ mean (SD) functional status score was higher, which indicated greater disability, at higher ADI quintiles for all 3 measures (eg, for MDHAQ quintile 1: 1.79 [1.87]; quintile 5: 2.43 [2.17]).

A total of 35,385 patients were included in the pooled adjusted longitudinal analysis, and the probability of functional decline was higher at higher ADI quintiles. About 18.9% (95% CI, 17.1%-20.7%) of patients had worse functional decline in the fifth ADI quintile, and 14.1% (95% CI, 12.5%-15.7%) of patients had worse functional decline in the first ADI quintile.

A mediation analysis included 2053 patients who had at least 1 Clinical Disease Activity Index score within 6 months before the baseline functional status score. RA disease activity mediated a small but statistically significant percentage (7%; 95% CI, 4%-22%) of the association between SES and functional decline in this longitudinal cohort.

Among several study limitations, the sample may not fully represent patients who are outside the registry and excluded from the analyses, which limits the generalizability of the findings. Also, the investigators were unable to account for adherence, RA severity or duration, or changes in SES over time.

“We found important disparities in functional status by SES in a national cohort of individuals with RA, despite utilization of rheumatology care,” the researchers commented. “We provide a framework for monitoring disparities in RA in rheumatology practices.”

Disclosure: Some of the study authors declared affiliations with biotech and pharmaceutical companies. Please see the original reference for a full list of authors’ disclosures.

Reference

Izadi Z, Li J, Evans M, et al. Socioeconomic disparities in functional status in a national sample of patients with rheumatoid arthritis. JAMA Netw Open. Published online August 2, 2021. doi:10.1001/jamanetworkopen.2021.19400