SM Kennedy, A Desjardins, A Kassam, M Ricketts and M Chan-Yeung
Department of Medicine, University of British Columbia, Vancouver, Canada.

Epidemiologic studies of occupational lung diseases generally compare symptoms and pulmonary function between groups with differing exposure risks. However, the functional consequences (e.g., on activities of daily life) of statistically significant group differences in either symptoms or pulmonary function are rarely addressed. An understanding of this is important for both the scientific investigators and users of these public health investigations. To address this issue, we developed a 15-item questionnaire to assess breathing-related limitations in activities of daily life, and applied this in a study of 112 retired workers. For each subject, we calculated a limitation score as the number of items associated with breathing difficulty divided by the total number of applicable items. Results from this questionnaire were compared to respiratory symptoms, the Sickness Impact Profile (SIP), lung function test results, 6-min walking distance, and participants' assessment of breathing effort after the walk. The limitation score was significantly higher in subjects reporting dyspnea (22% versus 4%, p < 0.01) or occasional wheeze (27% versus 6%, p < 0.01), and correlated negatively with FEV1, MMEF, and FEV1/FVC (R2 = -0.47, -0.36, and -0.45, respectively, p < 0.0001) and breathing effort after the 6-min walk (R2 = 0.31, p < 0.01). Breathing related limitation in daily activities was also associated with a general health related limitation in household maintenance and ambulation in the SIP (p < 0.01). For each questionnaire item, we compared the responses among subjects with a normal FEV1 to those of subjects with an abnormal FEV1 (below the lower 95% confidence limit).(ABSTRACT TRUNCATED AT 250 WORDS)