Cardiorespiratory Fitness as Mediator in the Association Between Physical Activity and Health-Related Quality of Life in Patients with CMD or OA

Purpose: Diseases like cardiovascular metabolic disease (CMD) and osteoarthritis (OA) impact health-related quality of life (hr-QoL). In the general population, hr-QoL is associated with physical activity (PA), sedentary time (ST) and cardiorespiratory fitness (CRF). This study aims to examine 1) associations between device-based and self-reported PA and ST, and hr-QoL, and 2) the influence of self-reported CRF in these associations in people with (or at risk for) CMD and/or OA. Methods: Data from the Lifestyle front Office For Integrating lifestyle medicine in the Treatment of patients (LOFIT) study was used. Participants included patients with (or at risk for) CMD and/or OA (n=273) within the Netherlands. PA and ST were measured using device-based (activPAL™) and self-reported methods (International Physical Activity Questionnaire – Short Form and Marshall Sitting Questionnaire). CRF was assessed by estimating peak oxygen uptake per kilogram bodyweight (VO 2peak mL·kg -1 ·min -1 ) using the FitMáx questionnaire. Hr-QoL was assessed using EQ-5D-5L. The associations were examined using linear regression and cross-sectional mediation models. Results: Higher levels of device-based, and self-reported PA were associated with higher hr-QoL ( b =0.007, 95% CI=0.000, 0.013 per 1000 steps, b =0.001 95% CI= 0.000, 0.002 per 30 minutes). Higher levels of device-based and self-reported ST were associated with lower hr-QoL ( b =-0.006, 95% CI=-0.012, -0.000 per 30 minutes, b =-0.004, 95% CI=-0.007, -0.001 per 30 minutes). A cross-sectional indirect association via CRF was observed in the association between PA and hr-QoL. Conclusions: Higher PA and lower ST are associated with enhanced hr-QoL, where CRF influences the relationship between PA and hr-QoL in this patient population. Reducing ST could be a more feasible first step, if increasing PA is challenging. Moreover, the influence of CRF emphasizes the need for interventions focusing on improving fitness levels.