Subjective measurement of activity in chronic obstructive pulmonary disease.

Activity is an essential part of life. Daily activities include caring for one's self and one's environment, moving about the home and community, and fulfilling various social roles. Personal fulfillment activities, such as interaction with others, hobbies, and attending social or entertainment events, play an important role in life satisfaction and well-being. Physical activity in the form of movement and exercise is essential for optimal fitness and health. Given these varied perspectives, what constitutes "activity" and how is it measured, both generally and in chronic obstructive pulmonary disease specifically? How should "activity" be measured as an outcome of treatment - pharmacologic, surgical, or rehabilitation? This paper discusses patient-reported measurement of activity, with specific reference to patients with chronic obstructive pulmonary disease. It begins with an overview of key measurement issues to consider when selecting or developing instruments, followed by clarification of two perspectives or classes of patient-reported activity assessment: functional and physical activity. Examples of measures designed to capture these concepts are provided. The paper concludes with recommendations for evaluating activity-related outcomes in patients with chronic obstructive pulmonary disease.