Objectives
This study aimed to examine the relationship between daily physical activity and the phase angle (PhA) obtained by bioelectrical impedance analysis (BIA) in rheumatoid arthritis (RA) patients.
Methods
Data from a prospective cohort study of RA patients who were surveyed every year were analyzed. The PhA was assessed by the BIA method, and physical activity was assessed as the amount of time of exercise in metabolic equivalents (METs) per day using a triaxial accelerometer for 7 consecutive days. The association between physical activity and the PhA was evaluated using the isotemporal substitution (IS) model in multiple regression analysis.
Results
Seventy-six RA patients were included in the analysis (81% female, age 66.2±13.1 years). On cross-sectional analysis, the IS model in multiple regression analysis showed that the PhA was 0.05 points higher every 10 minutes when activities with intensity of 1≤METs<2 were replaced by activities with intensity ≥3 METs (p=0.01). Over one year, the rate of change in the PhA was 0.69% higher every 10 minutes when activities with intensity of 1≤METs<2 were replaced by activities with intensity ≥3 METs (p=0.037).
Conclusions
The PhA in RA patients may be related to physical activity level.