Predictors of Clinical Stability and Mortality in COPD: A Longitudinal Study

Abstract

Background: There is no consensus on the definition of clinical stability in chronic obstructive pulmonary disease (COPD), and it is less frequently used as a treatment target compared to severe asthma. The factors that determine clinical stability and their effects on mortality are less well-studied in patients with COPD.

Methods: To address this gap, we conducted a prospective longitudinal cohort study to identify predictors of two-year clinical stability, defined as no exacerbations and stable symptoms (<2 point change in CAT score from baseline), and the impact of comorbid cardiovascular disease (CVD) on clinical stability and mortality in COPD patients.

Results: A total of 463 patients (mean age 71 ± 9 years) were enrolled in this study. The cohort was predominantly Chinese (81.7%) and 45.6% of participants were current smokers. The majority (55.7%) had a history of CVD. Approximately 36% of the cohort achieved clinical stability at one year, and one-third achieved stability at two years. Predictors of 2-year clinical stability included higher body mass index (BMI) (p<0.001), higher post-bronchodilator FEV1/FVC ratio (p=0.0132), fewer baseline exacerbations (p=0.007), absence of bronchiectasis (p=0.045), preserved hemoglobin levels (p=0.019), and successful smoking cessation (p=0.039). Notably, while 2-year clinical stability did not predict subsequent mortality, the presence of CVD was a significant predictor of 5-years mortality (HR 1.48, 95% CI 0.99-2.22; p=0.05).

Conclusion: Our study identified several predictors of 2-year clinical stability in patients with COPD. However, clinical stability at 2 years did not predict subsequent mortality. These findings suggest that clinical stability and mortality are distinct outcomes that are driven by different sets of predictive variables. This underscores the need for a comprehensive approach to COPD management that not only addresses exacerbations and symptoms, but also considers a broader range of factors influencing survival, particularly the management of comorbidities such as cardiovascular disease.

Keywords: South East Asia; cardiovascular disease; comorbidities; mortality; multi-ethnic; stability.

Figure 1

STROBE flowchart of study.

Figure 2

Scatter boxplot of illustrating the association of COPD duration with (A) GOLD spirometry grade, (B) GOLD ABE group, (C) presence (Yes) or absence (No) of cardiovascular disease and (D) presence (Yes) or absence (No) of bronchiectasis. Box plots indicate the median and interquartile range and the largest and smallest values above or below the 75^th and 25^th percentile, respectively. ***p<0.001,. ns: not significant **p<0.01, *p<0.05, ns: not significant.

Figure 3

Sankey plots illustrating the changes in the proportion of patients with (A) frequent exacerbation (FE), (B) CAT score of less than 10, and (C) clinical stability from baseline to 2 years of follow-up.

Figure 4

Kaplan-Meier curves illustrating the survival differences between (A) patients with (Y) and without (N) 2-year clinical stability and (B) cardiovascular disease (CVD). stable_2: 2-year clinical.