Differential changes in quality of life components over 5 years in chronic obstructive pulmonary disease patients

Abstract

Background: The aim of the study was to examine the longitudinal change in quality of life components of patients with chronic obstructive pulmonary disease (COPD).

Methods: In the Hokkaido COPD Cohort Study, 261 subjects were appropriately treated and followed over 5 years with a 74% follow-up rate at the end. The longitudinal changes in St George's Respiratory Questionnaire (SGRQ) scores were annually evaluated with forced expiratory volume in 1 second (FEV1). The subjects were classified into the rapid decliners, slow decliners, and sustainers based on ΔFEV1/year.

Results: The activity component of SGRQ generally deteriorated over time, and its annual decline was the greatest in the rapid decliners (<25th percentile). In contrast, the symptom component improved significantly year by year in the sustainers (>75 percentile), and it did not deteriorate even in the rapid decliners. Of the baseline data, predictors for worsening of the activity component were older age and lower body mass index. Larger reversibility was related to symptom component improvement. Of the follow-up data, ΔFEV1/year was the best predictor for worsening of the components of SGRQ. Continuous smoking was another factor for worsening of the activity component. For the symptom component, a history of exacerbation by admission definition was the determinant of its deterioration, whereas use of beta agonists was related to improvement.

Conclusion: The longitudinal changes of quality of life and their determinants are markedly different and independent between its components. The activity component of SGRQ generally deteriorated over years, while the symptom component rather improved in some patients with COPD under appropriate treatment.

Keywords: SGRQ; annual change; exacerbation; forced expiratory volume in 1 second; smoking.

Figure 1

The frequency distributions of the annual change in SGRQ (units/year). Notes: The calculated annual change in the SGRQ activity score is 1.22±3.53 (mean ± SD) (A), symptom score is −1.96±4.22 (B). Abbreviation: SGRQ, St George’s Respiratory Questionnaire; SD, standard deviation.

Figure 2

The relationship between the annual change in postbronchodilator FeV₁. Note: The annual change in SGRQ total score is negatively correlated with the annual change in FEV₁ (r=−0.27, P<0.001, n=261). Abbreviations: FEV₁, forced expiratory volume in 1 second; SGRQ, St George’s Respiratory Questionnaire.

Figure 3

The changes in the total and three component scores of the SGRQ during follow-up. Notes: Annual changes in the total score of SGRQ from baseline classified by annual change in FEV₁ (ml/year) during follow-up; The change from baseline in the SGRQ total score (mean ΔSGRQ ± SE) at 4-year follow-up: ΔSGRQ in rapid FEV₁ decliners, 5±2; slow FEV₁ decliners, 0±1, or FEV₁ sustainers, −4±2, and at 5-year follow-up: ΔSGRQ in rapid FEV₁ decliners, 5±2; slow FEV₁ decliners, 0±1; or FEV1 sustainers, −4±2 (A). Annual changes in the activity scores (B), symptom scores (C), and impact scores (D) of the SGRQ classified by annual change in postbronchodilator FEV₁ (ml/year) during follow-up are shown. P-values represent one-way analysis of variance with post hoc comparisons using Tukey’s multiple comparison tests at each year. Abbreviations: FEV₁, forced expiratory volume in 1 second; SGRQ, St George’s Respiratory Questionnaire; ΔSGRQ, change from baseline in the SGRQ; SE, standard error.