Key result
Rheumatoid arthritis linked to 1.7 mL/kg/min lower cardiorespiratory fitness, driven by physical symptoms and negative emotions.
Why the study?
Persons with rheumatoid arthritis have lower cardiorespiratory fitness than healthy individuals, but the variables explaining this association remained to be identified.
Does rheumatoid arthritis status associate with reduced estimated cardiorespiratory fitness, and is this mediated by physical symptoms and negative emotions?
Cross-Sectional (n=527)
Yes
Does rheumatoid arthritis status associate with reduced estimated cardiorespiratory fitness, and is this mediated by physical symptoms and negative emotions?
Effect estimate: Mean difference -1.7 mL/kg/min (95% CI -2.8 to -0.6)
Absolute Event Rate: 30.9% vs 39.8%
p-value: p=0.002
In patients with rheumatoid arthritis, reduced estimated cardiorespiratory fitness compared to healthy controls is largely mediated by physical symptoms and negative emotions, highlighting the need to address both physical and psychological factors to improve fitness.
Supports addressing symptoms and emotions in RA to mitigate lower fitness; hypothesis-generating pending prospective trials.
OBJECTIVES: Persons with rheumatoid arthritis (RA) have lower cardiorespiratory fitness (CRF) than healthy individuals. We sought to identify variables explaining the association between RA status and reduced CRF. METHODS: RA patients recruited from two Norwegian hospitals and blood donors recruited as controls filled in questionnaires about physical activity, physical symptoms, and psychological factors. Estimated CRF (eCRF) was calculated from non-exercise models. The relationship between RA status and reduced eCRF was explored with structural equation modelling. The latent variables physical symptoms (based on morning stiffness, joint pain, and pain in neck, back, or hips) and negative emotions (based on Hospital Anxiety and Depression Scale's Depression score and Cohen's perceived stress scale) were included as possible mediators between RA status and eCRF in separate and combined models adjusted for age and sex. RESULTS: Two-hundred-and-twenty-seven RA patients and 300 controls participated. The patients were older and had lower eCRF than controls (age- and sex-adjusted mean difference: 1.7 mL/kg/min, p=0.002). Both latent variables were significant mediators of the association between RA and reduced eCRF when included in separate models. The latent variables mediated 74% of the total effect of RA on eCRF in the combined model. Standardized coefficients: direct effect of RA -0.024 (p=0.46), indirect effect through physical symptoms -0.034 (p=0.051), and indirect effect through negative emotions -0.034 (p=0.039). CONCLUSION: Both physical symptoms and negative emotions mediated the association between RA and reduced eCRF with similar effect sizes. To successfully increase CRF in RA patients, both physical and psychological factors should be addressed. Key Points • The RA patients in the present study had 1.7 mL/kg/min lower mean estimated cardiorespiratory fitness (CRF) compared to healthy controls. • Mediation analysis demonstrated that physical symptoms and negative emotions mediated 74% of the total negative effect of RA on estimated CRF in a combined, adjusted model. • This suggests that both physical and psychological factors should be addressed when supporting RA patients in improving their CRF.
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Houge et al. (2023) conducted a cross-sectional in Rheumatoid arthritis (n=527). Rheumatoid arthritis vs. Healthy controls was evaluated on Estimated cardiorespiratory fitness (eCRF) (Mean difference -1.7 mL/kg/min, 95% CI -2.8 to -0.6, p=0.002). Rheumatoid arthritis was associated with a 1.7 mL/kg/min lower estimated cardiorespiratory fitness compared to controls, with 74% of this effect mediated by physical symptoms and negative emotions.
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