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Abstract
Introduction and Objectives Hospitalisation for an exacerbation of chronic respiratory disease has a major impact on physical activity (PA). However, criteria to derive reliable inpatient PA data do not exist and current recommendations are unlikely to account for variations in length of hospital stay (LOHS) and the hospital environment. The aims were to identify the minimum wear time and number of days required to obtain reliable inpatient PA data; to use these criteria to determine how PA changes during recovery as an inpatient; and to compare PA across patients stratified by LOHS.
Methods 259 individuals hospitalised with an exacerbation of chronic respiratory disease were recruited as part of an early rehabilitation trial previously reported (Greening et al, BMJ 2014). Participants (mean (SD) age 70.0±9.7 years, 58.3% female) wore a physical activity monitor (SenseWear) during their stay. Daily step count and walking time during waking hours was analysed. Inpatient PA was assessed across a range of minimum wear time criteria (≥1–12 hours). Repeated measures analysis of covariance was used to compare between days and between times of day. Single-day intraclass correlation coefficients (ICCs) were calculated across the range of wear time criteria. The minimum number of days required to obtain an ICC ≥0.80 was estimated using the Spearman-Brown prophecy formula.
Step count per hour as a proportion of total daily step count across an average 24 hour period. Data are reported as mean (95% CI).
Results A minimum wear time of 11 hours (≥1 valid day) allowed 80% of the sample to be retained. All minimum wear time thresholds produced an ICC ≥0.80, resulting in 1 day of wear required to produce representative inpatient PA. Mornings and afternoons were more active than evenings and overnight (32.1% and 32.0% vs. 25.2% and 10.7% of steps/day, respectively, p<0.001) (figure 1). No changes in PA were observed during the hospital stay; ranging 585–707 steps/day and 72–83 min/day of walking. After controlling for wear time, patients admitted for 2–3 days took more steps on average than patients staying 7–14 days (997±125 vs. 597±91, p=0.036).
Conclusions One full day (24 hours) of monitoring is required at the individual-level to obtain representative inpatient PA. A minimum wear time criteria of ≥11 waking hours is recommended for sample-level data. Wear time and LOHS should be accounted for in analyses.