Background Patients with Rheumatoid Arthritis (RA) are at increased risk for cardiovascular disease (CVD). Research suggests impaired vascular function contributes to this heightened risk. At present, little is known regarding factors associated with vascular function in RA. Epidemiological evidence demonstrates sedentary behaviour (i.e., waking behaviour ≤1.5 metabolic equivalents whilst sitting or lying), to be adversely linked to CVD risk in the general population. Whilst the biological processes underlying this relationship are not understood, vascular dysfunction may play a role (1, 2). However, research is yet to examine the association between sedentary behaviour and vascular function in healthy adults and/or clinical populations. Studies investigating this relationship in RA, will help to determine the extent to which sedentary behaviour may represent a modifiable risk factor for CVD in these patients.
Objectives To investigate the cross-sectional associations between sedentary behaviour and microvascular and large vessel endothelial function among patients with RA.
Methods Fifty-three patients with RA participated in the study (M age=52.9±12.8, 72% female). Laser Doppler imaging with iontophoresis was used to assess microvascular endothelium-dependent (acetylcholine, ACh) and endothelium-independent (sodium nitroprusside, SNP) function. Large vessel endothelium-dependent and endothelium-independent functions were measured via flow-mediated dilation (FMD) and glyceryl trinitrate dilation (GTN), respectively. Sedentary behaviour was self-reported via the International Physical Activity Questionnaire (hours/week sitting). Data were analysed using multiple linear regressions adjusted for traditional CVD risk factors; age, gender, total cholesterol, smoking status, family history of CVD, hypertension and body-mass-index.
Results Sitting time (hours/week, M =39.2±17.9) was significantly negatively related to % increase in perfusion in response to ACh (β=−0.30, p<0.05) and SNP (β=−0.37, p<0.01) after adjustment for traditional CVD risk factors. Sitting time accounted for 8% and 12% of the variance in microvascular endothelium-dependent function (ACh) and endothelium-independent function (SNP), respectively (traditional CVD risk factors, R2=0.3). No significant associations were observed between self-reported sitting time and large vessel endothelium-dependent vasodilation (FMD, β=0.16, p=0.29) or independent vasodilation (GTN, β=−0.08, p=0.55).
Conclusions Sedentary behaviour appears to adversely affect microvascular endothelial function, but not large vessel function in patients with RA. It may therefore represent a modifiable risk factor for CVD in this population. Experimental studies employing objective measures of sedentary behaviour are necessary to confirm these findings, and to determine the utility of sedentary behaviour interventions for improving vascular function and reducing CVD risk in RA.
Thosar SS, Bielko SL, Mather KJ, et al. Effect of Prolonged Sitting and Breaks in Sitting Time on Endothelial Function. Med Sci Sports Exerc 2015:47(4);843–9.
Fenton SAM & Kitas GD. Rheumatoid Arthritis: Sedentary behaviour in RA – a new research agenda. Nat Rev Rheumatol 2016:12(12):698–700.
Disclosure of Interest None declared