Self-reported and objectively measured physical activity in adults with systemic lupus erythematosus

Most estimates of physical activity (PA) patterns in systemic lupus erythematosus (SLE) are based on subjective self-report measures prone to error. The aims of this study were to obtain objective measurements of PA using an accelerometer and estimates of energy expenditure based on the self-reported International Physical Activity Questionnaire (IPAQ), and to describe their relationship.

The Activity in Lupus To Energize and Renew study, a cross-sectional study of PA, included 129 persons with SLE. Accelerometer measures >7 days included total daily activity counts and minutes of moderate-vigorous PA (MVPA). Each person completed the IPAQ via telephone interview. Spearman's correlations (r) and 95% confidence intervals (95% CIs) assessed associations between accelerometer and IPAQ.

Daily PA means and SDs from accelerometer measures were 502,910 ± 118,755 for total daily activity counts and 40 ± 30 minutes for MVPA. The median (interquartile range) MET minutes/day for IPAQ intensities were: 400 (159-693) for total; 83 (26-184) for walking; and 231 (77-514) for MVPA, and domains were: 0 (0-73) for work; 28 (0-85) for active transportation; 77 (26-231) for domestic and garden; and 57 (0-213) for leisure. Associations between accelerometer measures and IPAQ were 1) total daily count versus IPAQ total: r = 0.21 (95% CI 0.03, 0.37) and 2) MVPA versus IPAQ moderate-vigorous: r = 0.16 (95% CI - 230.02, 0.33).

Accelerometer measures and IPAQ energy expenditure estimates were moderately correlated. IPAQ provided descriptive PA data, whereas accelerometers captured all daily activities, which can help assess guideline attainment. The choice of IPAQ versus accelerometer measure should include considering the purpose for which PA is measured.