The sedentary behaviour and physical activity patterns of survivors of a critical illness over their acute hospitalisation: an observational study

Background: Physical function is often poor in intensive care unit (ICU) survivors, yet objective descriptions of sedentary behaviour and physical activity during acute hospitalisation are lacking. Objective: The objective of this study was to examine sedentary and activity patterns during patients' hospital-based recovery from a critical illness and associations with physical function, muscle strength, and length of stay (LOS). Methods: This was a prospective cohort study in a tertiary ICU and acute hospital wards, which recruited 40 adults who required ≥5 days of mechanical ventilation. Data were collected at awakening (T1), ICU discharge (T2), and hospital discharge (T3), which included monitoring of body posture (sedentary behaviour) using the activPAL and activity intensity using the GENEActiv. Data were reported as time spent lying/sitting and upright, with the number of sit-to-stand transitions and upright bouts. Statistical analysis was conducted using repeated-measures analysis of variance and Spearman's rho. Results: From awakening to hospital discharge (T1–T3, n = 23), there was a mean [95% confidence interval] decrease in % time spent lying/sitting (−3.0% [-4.6% to1.4%], p ≤ 0.001) corresponding to increased time spent upright (43.0 min [19.9, 66.1], p ≤ 0.001). Sit-to-stand transitions increased (18 [11, 28], p ≤ 0.001). The number of upright bouts ≥2 and ≥ 5 min increased (both p ≤ 0.001), but only from ICU to hospital discharge (T2-T3, 5.3 [3.1, 7.6] and 2.3 [0.9, 3.8] respectively). At ICU discharge (T2), less % of time spent lying/sitting, more minutes spent upright, and more transitions were associated with better physical function (Physical Function in Intensive Care Test-scored and de Morton Mobility Index; all rho ≥+/−0.730, p ≤ 0.001) and muscle strength (hand grip, Medical Research Council sum-score; all rho≥+/−0.505, p ≤ 0.001). There were no associations between accelerometry and hospital LOS. Conclusions: ICU survivors' transition from highly sedentary behaviour to low intensity activity over their acute hospitalisation. Sedentary breaks may be not spread over the day such that modifying sedentary behaviour to break up prolonged lying/sitting may be a focus for future research. Clinical trial registration: NCT02881801