Assessment of sedentary behaviour in individuals with COPD: how many days are necessary?

Objective: The objective of the present study was to define the minimum number of monitoring days required for the adequate cross-sectional assessment of sedentary behaviour in individuals with chronic obstructive pulmonary disease (COPD). Methods: In this cross-sectional study, the sedentary behaviour of individuals with COPD was assessed using two physical activity monitors during awake time for seven consecutive days. Time spent per day in activities requiring ≤1.5 metabolic equivalents (METs) and in sitting, lying and sitting+lying positions was calculated taking into account the average of 7 days (as a reference in all analyses) and of all 119 possible combinations of 2---6 days. Intraclass correlation coefficients (ICCs) and linear regression analyses were performed for all combinations. Results: 91 individuals were analysed (47 female, 66±9 years, forced expiratory volume in 1 s 50±15% predicted). For the variables time spent per day in activities ≤1.5METs and sitting, the average of any combination of at least four assessment days was sufficient to adequately reflect the average of 7 days (adjusted R2≥0.929, ICC≥0.962, p<0.0001 for all). For time spent per day lying and sitting+lying, only two assessment days were enough (adjusted R2≥0.937, ICC≥0.968, p<0.0001 for all). Results were maintained independently of patient sex, disease severity, day of the week, daylight time or daytime naps. Conclusions: The average of 4 days of objective monitoring was sufficient to adequately reflect the results of a 1-week assessment of the main outcomes related to sedentary behaviour in individuals with moderate to very severe COPD, regardless of sex, disease severity, day of the week, daylight time and occurrence of daytime naps.

Tossing and turning: association of sleep quantity-quality with physical activity in COPD.

The association between characteristics of sleep and physical activity in daily life (PADL) has not yet been investigated in depth in subjects with COPD. This study evaluated whether time spent per day in physical activity (PA) and sedentary behaviour are associated with sleep quantity and quality in this population. Sleep and PADL were objectively assessed by an activity monitor for 7 days and analysed on a minute-by-minute basis. Subjects also underwent spirometry and 6-min walking test (6MWT). Fifty-five subjects with moderate-to-severe COPD (28 male, 67±8 years) were studied. Subjects with total time in bed (TIB) per night ≥9 h had higher wake-after-sleep onset than TIB 7-9 h and TIB ≤7 h (195 (147-218) versus 117 (75-167) and 106 (84-156) min) and more fragmented sleep than TIB ≤7 h (8.2 (6.7-14.3) versus 6.3 (5.6-6.9) sleeping bouts; p<0.05 for all). Subjects with TIB ≥9 h also spent more time per day in sedentary behaviour and less time per day in PA of light and moderate-to-vigorous intensity than those with TIB 7-9 h and ≤7 h. In multiple linear regression, TIB ≥9 h was the only significant predictor of physical inactivity (ß=-3.3 (-5.1, -1.6), p≤0.0001), accounting for 20% of its variation. Sleep fragmentation was frequent and more pronounced in physically inactive than active patients (7.5 (6.3-9.6) versus 6.4 (5.5-7.3) sleeping bouts; p=0.027). In summary, subjects with COPD with TIB ≥9 h·night-1 have more fragmented sleep, are more sedentary and less physically active than those with <9 h·night-1, independently of the awake time. Sleep quality is frequently poor and even worse in patients classified as physically inactive.