Determinant factors of sedentary time in individuals with COPD

The factors influencing sedentary time (ST) of individuals with chronic obstructive pulmonary disease (COPD) have not been thoroughly explored.

To identify determinant factors of ST in individuals with stable COPD.

Individuals with COPD had their ST and variables of physical activity (PA) cross-sectionally assessed during seven days with an activity monitor. Main variables were ST/day (<1.5 METs), steps/day, time/day in light PA (light PA/day, 1.5-2.9 METs) and in moderate-to-vigorous PA (MVPA/day, ≥3 METs). Additional assessments included 6-min walking test (6MWT), Medical Research Council (MRC) scale, lung function and body composition. Multiple linear regression models were built with variables correlating significantly with ST/day.

50 individuals were analyzed (44 % males; 66 ± 8 years; FEV₁ 50 ± 19%pred). ST/day was 488 ± 160 min (61 ± 15 % of the day). 6MWT, MRC scale, MVPA/day, steps/day and light PA/day correlated significantly with ST expressed as minutes/day or as % of the day. In the multiple regression analyses, variables explaining the variance of ST in minutes/day were MRC scale (1 %) and light PA/day (53 %) (model R² = .541, p < 0.001) and of ST in % of the day were steps/day (53 %) and light PA/day (46 %) (model R² = .994, p < 0.001).

In individuals with COPD, the variance in sedentary time can be explained by dyspnea in daily life, step count and specially time/day in light PA, which reinforces the increase in light PA (rather than necessarily MVPA) as a strategy to reduce sedentary time.