Strength of associations of psoriatic arthritis and physical activity with body composition: the population-based Trøndelag Health study

INTRODUCTION: Psoriatic arthritis (PsA) and low physical activity (PA) negatively influence body composition. We examined the relative strength of associations of PA and PsA with body composition in individuals with PsA compared to controls, and comparing PA assessment by self-report versus a device. METHODS: We analyzed data from 142 individuals with PsA and 23 858 controls who participated in the fourth survey of the Trøndelag Health study (HUNT4, 2017-2019). Standardized multivariable linear regression models were used to assess the relative strength of associations of PsA (CASPAR criteria) and PA with visceral fat mass and percentage body fat measured by bioelectrical impedance analysis. PA was either self-reported (exercise frequency, duration and intensity) or device-measured using accelerometers. Model fit was compared using Akaike's Information Criterion and the Bayesian Information Criterion. RESULTS: Standardized regression coefficients for PsA had much smaller absolute values than those for performing PA in explaining variations in body composition (visceral fat mass: PsA: 0.017 to 0.019, PA: -0.14 to -0.31; percentage body fat: PsA 0.013 to 0.015, PA: -0.12 to -0.29). Unstandardized models showed that performing moderate to high levels of PA could compensate for the unfavorable body composition associated with PsA. Models with device-measured PA had substantially better fit than those with self-report, indicating that they better captured the variations in body composition. CONCLUSION: PA explained larger variations in body composition than PsA. Individuals with PsA should be informed that engaging in PA has a greater positive impact on body composition than the negative consequences of having PsA. Key Points • Low physical activity was more strongly associated with an unfavourable body composition than psoriatic arthritis. • Device-measured physical activity more accurately captured the associations between physical activity and body composition than self-reported measures. • Promoting physical activity and perhaps use of wearable devices to record it may potentially help individuals with psoriatic arthritis mitigate the unfavorable body composition associated with their arthritis.