Abstract
BACKGROUND: Rheumatoid arthritis (RA) causes pain, fatigue, joint deformity, disability, and an increased risk for serious sequelae, often despite treatment, in 1.3 million Americans. RA is affected by numerous biopsychosocial determinants, which greatly complicate treatment, including altered efficacy. OBJECTIVE: The purpose of this study is to examine associations between individual biopsychosocial determinants, diet quality, gastrointestinal (GI) health, and disease activity in adults with RA. METHODS: This cross-sectional, descriptive study has been approved by the Northern Arizona University Internal Review Board (# 2111208-12). We will include 96 adults with RA recruited from across Arizona using social media and community events (through the Arthritis Foundation) and various primary care and rheumatology practices in Flagstaff and the greater Phoenix metro area. Individual biopsychosocial factors will be measured with a demographic survey and direct measures. The Arizona Food Frequency Questionnaire will measure dietary intake for the past 6 months, and Healthy Eating Index-2020 scores will be calculated from these data. The Automated Self-Administered 24-hour diet recall will measure recent dietary intake. Fecal analyses for gut microbiome diversity and composition and fecal calprotectin will measure current GI health. Disease activity will be measured by the Health Assessment Questionnaire-Disability Index and pain scale, Disease Activity Score of 28 Joints, and hematology results (C-reactive protein and erythrocyte sedimentation rate). In addition to descriptive statistics, hierarchical linear regression will examine hypothesized associations between diet quality, GI health, and disease activity. We hypothesize that individual biopsychosocial determinants will be associated with diet quality, which will be indirectly associated with disease activity through gut microbiome diversity and level of GI inflammation in adults with RA. RESULTS: This study was funded in February 2024. As of December 19, 2025, a total of 80 individuals have been recruited. Data analysis has not yet commenced at the time of manuscript submission. Study results are expected to be published in fall 2026. CONCLUSIONS: RA is a complicated disease that impacts millions. Few individuals reach sustained remission, even while following provider recommendations. A better understanding of the various factors that impact this complicated disease has the potential to support changes in research and care that will improve the lives of people with RA. The knowledge gained in this study will provide a foundation to inform future interventional research targeting diet quality to support GI health and decrease RA disease activity. Further, the details of this research plan provide methodological resources for other RA researchers, and research results have the potential to improve communication between rheumatology providers and patients. INTERNATIONAL REGISTERED REPORT IDENTIFIER (IRRID): PRR1-10.2196/79889.