Directly-Measured Physical Activity Predicts Re-Hospitalization Within Thirty Days Following Discharge For A COPD Exacerbation

Background: Lower levels of physical activity are related to increased health care utilization and mortality risk in patients with COPD. Since re-hospitalization within 30 days following discharge for a COPD exacerbation is considered an important outcome, we evaluated the relationship between physical activity and 30-day readmission.

Methods: Thirty-four patients discharged following a hospitalization for a clinically-defined COPD exacerbation at a community hospital were studied. Prior to discharge, spirometry was performed and a six minute walk test distance (6MWD) was measured. At discharge, patients were asked to wear an activity monitor (ActiGraph GT3X+) on the non-dominant wrist for 4 consecutive weeks or until they were re-hospitalized. Vector magnitude units (VMU), the sum of movements in three planes over each minute, were used to quantify activity. Physical activity over the first week was dichotomized as ‘higher’ or ‘lower’ depending on whether the mean number of minutes per day with VMU > 3000 was above or below 60.

Results: The mean FEV1 was 42% (range, 23 to 70%) and the 6MWD was 127 m (range, 0 to 345 m). Twelve patients (35%) had all-cause readmissions within 30 days. Those patients with two or more hospitalizations for COPD in the preceding year were more likely to be hospitalized within 30 days: odds ratio (OR) = 9.5, 95% confidence interval (CI) = 1.9, 46.9, p = 0.006. Sixteen patients (43%) had lower levels of physical activity, defined as <60 minutes per day when VMU were > or = 3000 counts. Patients with lower activity had a higher 30-day readmission rate than those with higher levels of activity: 56% vs 14%, OR =7.7, 95% CI: 1:6 to 37.1, p=0.01. FEV1 and 6MWD did not predict readmission.