Longitudinal changes in health status using the Chronic Respiratory Disease Questionnaire and pulmonary function in patients with stable Chronic Obstructive Pulmonary Disease

Long-term changes in health status have been less evaluated in patients with chronic obstructive pulmonary disease ( COPD), in comparison to the changes in forced expiratory volume in 1 s (FEV1). Accordingly, we examined the clinical course of health status as well as pulmonary function in COPD patients, and investigated the relationship between the change in health status and the change in pulmonary function in a 3-year longitudinal study involving 224 patients with COPD. Health status using the Chronic Respiratory Disease Questionnaire (CRQ) and pulmonary function were measured at baseline and every six months over three years. We used the random effects model for the slopes to estimate the longitudinal changes. A total of 147 patients completed the 3-year study. The dyspnoea, fatigue, and emotional function domains of the CRQ declined slowly but significantly over 3 years (p = 0.001, 0.003, and 0.004, respectively) with a mean decline rate of 0.08/year. This means that it would take about 6 years to reach the minimal important change of 0.5 on the CRQ. The mean decline in post-bronchodilator FEV1 was 60 ml/year. None of the changes in any of the domains of the CRQ were significantly correlated with the changes in pulmonary function. We have found that, in comparison to the decline in pulmonary function, health status evaluated by the CRQ declined significantly but very slowly in three of four domains over three years in patients with COPD. Furthermore, we have demonstrated that there was no significant relationship between the change in health status and the change in pulmonary function.