Sedentary behaviour in rheumatoid arthritis: definition, measurement and implications for health.

RA is a chronic autoimmune disease characterized by high grade-inflammation, and associated with elevated cardiovascular risk, rheumatoid-cachexia and functional impairment. Sedentary behaviour (SB) is linked to heightened inflammation, and is highly pervasive in RA, likely as a result of compromised physical function and persistent fatigue. This high sedentarity may exacerbate the inflammatory process in RA, and hold relevance for disease-related outcomes. The aim of this narrative review is to provide an overview of the definition, measurement and health relevance of SB in the context of RA. Contradictions are highlighted with regard to the manner in which SB is operationalized, and the significance of SB for disease outcomes in RA is outlined. The advantages and disadvantages of SB measurement approaches are also discussed. Against this background, we summarize studies that have reported SB and its health correlates in RA, and propose directions for future research.