Relationship between exacerbation frequency and lung function decline in chronic obstructive pulmonary disease

TLDR

Chronic obstructive pulmonary disease is marked by an accelerated decline in lung function accompanied by episodic exacerbations that worsen symptoms. This study aimed to determine whether the frequency of exacerbations is associated with the rate of lung function decline in COPD patients. Over four years, 109 COPD patients performed daily home measurements of peak expiratory flow and symptoms, and exacerbations were identified from symptom reports, with cross‑sectional random‑effects models comparing lung function decline between patients with frequent (>2.92 per year) and infrequent exacerbations. Patients experiencing frequent exacerbations exhibited a markedly faster decline in FEV1 (–40.1 ml yr⁻¹ vs –32.1 ml yr⁻¹) and PEF (–2.9 l min⁻¹ yr⁻¹ vs –0.7 l min⁻¹ yr⁻¹), had greater FEV1 loss when smoking status was accounted for, were more often hospitalized with longer stays, and showed consistent exacerbation patterns within individuals, indicating that exacerbation frequency drives long‑term lung function deterioration.

Abstract

<b>Background:</b> Chronic obstructive pulmonary disease (COPD) is characterised by both an accelerated decline in lung function and periods of acute deterioration in symptoms termed exacerbations. The aim of this study was to investigate whether these are related. <b>Methods:</b> Over 4 years, peak expiratory flow (PEF) and symptoms were measured at home daily by 109 patients with COPD (81 men; median (IQR) age 68.1 (63–74) years; arterial oxygen tension (Pao₂) 9.00 (8.3–9.5) kPa, forced expiratory volume in 1 second (FEV₁) 1.00 (0.7–1.3) l, forced vital capacity (FVC) 2.51 (1.9–3.0) l); of these, 32 (29 men) recorded daily FEV₁. Exacerbations were identified from symptoms and the effect of frequent or infrequent exacerbations (&gt; or &lt; 2.92 per year) on lung function decline was examined using cross sectional, random effects models. <b>Results:</b> The 109 patients experienced 757 exacerbations. Patients with frequent exacerbations had a significantly faster decline in FEV₁ and peak expiratory flow (PEF) of –40.1 ml/year (n=16) and –2.9 l/min/year (n=46) than infrequent exacerbators in whom FEV₁ changed by –32.1 ml/year (n=16) and PEF by –0.7 l/min/year (n=63). Frequent exacerbators also had a greater decline in FEV₁ if allowance was made for smoking status. Patients with frequent exacerbations were more often admitted to hospital with longer length of stay. Frequent exacerbations were a consistent feature within a patient, with their number positively correlated (between years 1 and 2, 2 and 3, 3 and 4). <b>Conclusions:</b> These results suggest that the frequency of exacerbations contributes to long term decline in lung function of patients with moderate to severe COPD.