Longitudinal changes in directly measured physical activity in patients with chronic obstructive pulmonary disease: the trajectory of change.
OBJECTIVE
Chronic obstructive pulmonary disease (COPD) is a systemic disease with various outcomes of importance, for example, exercise capacity and dyspnea. These variables may follow different trajectories over time. It is established that physical activity decreases in COPD, although its process over time has not been evaluated. Accordingly, we compared longitudinal changes in physical activity with changes in standard outcome assessments: forced expiratory volume in 1 second (FEV(1)), 6-minute walk distance, and dyspnea.


METHODS
Physical activity was measured with tri-axial accelerometers worn on a lateral position at the waist for 7 consecutive days. Nonuse was eliminated using a computer algorithm for this device. Activity was assessed in 2 ways: (1) as vector magnitude units (VMU), the sum of movements per minute in 3 planes, and (2) VM250, the percent of time worn when VMU was 250 or more counts per minute. Eighteen patients with COPD (FEV(1) 61 ± 17% predicted) from a larger population were restudied. The interval between the baseline and followup assessments was 609 ± 58 days.


RESULTS
Mean VMU at followup was less than at baseline: 146 ± 70 vs 198 ± 85 counts per minute, respectively (P = .002). VM250 was also reduced: 19 ± 9% vs 25 ± 11%, respectively (P = .003). There was no significant longitudinal change in FEV(1). The 6-minute walk distance decreased by 39 m (P = .04). The Medical Research Council dyspnea increased by 0.5 units (P = .04).


CONCLUSIONS
Directly measured physical activity decreases over time in COPD, similar to other outcomes of importance.
Pulmonary and Critical Care, Thomas Jefferson University Hospital, Philadelphia, Pennsylvania 19107, USA. dr.vanjul@gmail.com
Vanjul
V
Agarwal
Sodieyne
S
Tetenta
Jennifer
J
Bautista
Richard
R
ZuWallack
Bimalin
B
Lahiri
D000054:Acceleration; D000368:Aged; D000465:Algorithms; D018450:Disease Progression; D005260:Female; D006801:Humans; D008297:Male; D008991:Monitoring, Physiologic / Q000379:methods; D009043:Motor Activity / Q000502:physiology*; D029424:Pulmonary Disease, Chronic Obstructive / Q000175:diagnosis / Q000473:pathology* / Q000523:psychology; D036301:Qualitative Research; D013223:Statistics as Topic; D013997:Time Factors