Physical Activity, Spirometry and Quality-of-Life in Chronic Obstructive Pulmonary Disease

In Australia, as in many other countries, COPD represents a substantial burden of disease, being the fourth highest cause of death and the fourth highest cause of morbidity among those > 65 years. In recent years, approaches to the management of COPD acknowledge that although the primary impairment is respiratory, important, potentially reversible secondary impairments occur that manifest as reductions in exercise capacity and health related quality-of-life (HRQL) ([1], [2]). As a consequence, valid, reproducible and interpretable outcomes have been developed to monitor the effectiveness of addressing these secondary impairments.

In the latest edition of the journal, McGlone and colleagues, from the University of Tasmania ([2]) point out that although HRQL correlates broadly with exercise capacity as measured by timed walk tests or constant power endurance, less is known of the relationship between HRQL and physical function when the latter is measured by self-administered questionnaires or motion sensors. The emphasis on walking ability is relevant as it is so closely tied to daily living.

In Hobart Southern Tasmania (pop 195,000) 21% of the general practitioners agreed to participate in a study which ultimately enrolled 124 COPD patients > 50 years. HRQL was assessed using the self administered St. George's Respiratory Questionnaire (SGRQ) and walking was measured with a simple pedometer as steps per day, over each of 7 days. In addition, non-walking exercise such as time spent swimming, cycling or upper body exercise, was recorded over the same period.

The subjects were predominantly elderly, retired men and just over a quarter had participated in a rehabilitation program. Physical activity of 3621 steps per day for men and 4,287 for women was approximately half that of healthy individuals ([3]). The steps per day decreased gradually with age, but were consistently greater among those who also participated in non-walking exercise activities, even though the latter did not influence HRQL. There were weak but significant correlations between the FEV₁ expressed as % predicted, the physical activity scores and the SGRQ, most notably the activities sub-component.

There is naturally a broad relationship between activities of any kind and the severity of airflow limitation, those with the worst disease being the most short of breath and therefore the least able to engage in physical activity. However, since this relationship is weak, airflow limitation cannot be used as a surrogate measure of either exercise capacity or quality-of-life as each represents a distinct domain that should be measured independently. The use of a pedometer to measure steps walked per day is interesting as it brings us closer to the actual physical activity likely to be limited in most patients with COPD. In another disease specific measure, the chronic respiratory questionnaire, ([4]) when the domain of dyspnea is constructed by asking the patient to identify 5 activities limited by breathlessness, walking is frequently identified as a key activity.

Pedometers are relatively simple devices, inexpensive and easy to calibrate ([5]). Although their ability to distinguish among the various body movements is limited, when calibrated daily and used specifically for walking, they do provide valuable information. By emphasizing the relationship among airflow limitation, steps walked and HRQL, this report highlights that even in a community environment, by using simple, testing equipment plus appropriate questionnaires, the individual domains of respiratory impairment, physical activity and HRQL can and should be measured, as they provide information that may be useful in evaluating the effectiveness of the management of COPD.