Background Rheumatoid Arthritis (RA) is associated with increased risk of cardiovascular disease (CVD). Recent evidence suggests sedentary behaviour (waking behaviour ≤1.5 metabolic equivalents whilst sitting/lying) may contribute towards the progression of RA outcomes, including heightened CVD risk (1). Sedentary behaviour occupies the majority of waking hours among people with RA (1). However, the proportion of time spent sedentary is likely to fluctuate over the course of the day, with periods of high sedentarity representing more optimal opportunity for intervention, and thus potentially higher intervention efficacy.
Objectives The aims of this study were; 1) to explore temporal patterns of sedentary behaviour (and physical activity) among RA patients, and 2) to examine associations between temporal sedentary patterns and predicted 10-year risk of CVD.
Methods Patients with RA (N=97) wore a GT3X accelerometer for 7 days to assess habitual sedentary time (<100 counts/min) and physical activity (PA; light =100–2019, moderate-to-vigorous = ≥2020 counts/min). Accelerometer data were analysed separately for each hour (valid hour criteria; 60-minutes of data on ≥3 days, including a weekend day). To evaluate 10-year risk of CVD (Q-risk2), patients reported their medical history, provided a fasted blood sample and underwent assessments of blood pressure and body-mass index.
Results Temporal patterns of sedentary time and PA are reported in Figure 1. Sedentary time declined throughout the morning (08:00–12:00). During the afternoon, sedentary time increased by 4.5 minutes (12:00–18:00; M =34.36±8.86 to M =39.06±7.91). A more marked increase in sedentary time was observed during leisure time (18:00–22:00; M =39.61±7.59 to M =47.90±6.30). Repeated measures analysis of variance (ANOVA) revealed sedentary time was significantly higher during leisure time (M =46.20±5.46) compared to the morning (M =36.88±5.61), and afternoon (M =38.50±6.07) [N =28, F(2,26)=43.48, p=<0.01]. Significant differences remained after accounting for employment status (i.e., employed vs. unemployed/student, F(2,23)=1.40, p=0.27). Patients who accumulated M = ≥45.31 sedentary minutes during their leisure time (18:00–23:00, median split), had significantly higher 10-year risk of CVD (M =22.23±13.83) compared to those accruing M=<45.31 sedentary minutes (M=8.09±7.62) [t(41)=3.92, p=<0.01]. Finally, hourly patterns for light PA were the reverse of those observed for sedentary time. Hourly MVPA engagement was consistently <3 minutes (peak MVPA at 09:00–10:00, M =2.47±4.16).
Conclusions Interventions targeting leisure time sedentary behaviour (18:00–23:00), relative to more occupational sedentary behaviour (08:00–18:00), may offer the greatest potential for sedentary time reduction and associated improvements of CVD risk profile. Due to inverse patterns of engagement, replacing leisure time sedentary behaviour with light PA may offer an effective intervention approach.
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