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Original article
Time course and pattern of COPD exacerbation onset
  1. Shawn D Aaron1,
  2. Gavin C Donaldson2,
  3. George A Whitmore1,3,
  4. John R Hurst2,
  5. Tim Ramsay1,
  6. Jadwiga A Wedzicha2
  1. 1Department of Medicine, The Ottawa Hospital Research Institute, Ottawa, Ontario, Canada
  2. 2Department of Medicine, University College London Medical School, London, UK
  3. 3Department of Economics, McGill University, Montreal, Quebec, Canada
  1. Correspondence to Dr Shawn D Aaron, The Ottawa Hospital, General Campus, 501 Smyth Road, Ottawa, ON K1H 8L6, Canada; saaron{at}


Background The natural history and time course of the onset of exacerbation events of chronic obstructive pulmonary disease (COPD) is incompletely understood.

Methods A prospective cohort of 212 patients with COPD was monitored using daily symptom diaries for a median of 2.8 years to characterise the time course of COPD exacerbation onset. Decision rules based on weighted self-reported symptoms were used to define opening and closing of exacerbation events. Event time intervals were analysed and logistic regression was used to determine the effects of patient covariates on exacerbation events.

Results Patients recorded 4439 episodes of worsening respiratory symptoms from baseline; 2444 (55%) events resolved spontaneously and 1995 (45%) resulted in a COPD exacerbation. In 1115 of the 1995 COPD exacerbations (56%) the onset was sudden and the exacerbation threshold was crossed on the same day symptoms began. In contrast, 44% of exacerbations were characterised by gradual onset of symptoms (median duration from symptom onset to exacerbation 4 days). Patients who experienced sudden onset exacerbations had greater mean daily symptom scores (7.86 vs 6.55 points, p<0.001), greater peak symptom scores (10.7 vs 10.2 points, p=0.003), earlier peak symptoms (4.5 vs 8.0 days, p<0.001) and shorter median recovery times back to baseline health status (11 vs 13 days, p<0.001). Multivariable analysis showed that gradual onset exacerbations were statistically associated with a longer duration of exacerbation recovery (OR 1.28, 95% CI 1.06 to 1.54, p=0.010).

Conclusions COPD exacerbations exhibit two distinct patterns—sudden and gradual onset. Sudden onset exacerbations are associated with increased respiratory symptoms but shorter exacerbation recovery times.

  • Chronic obstructive pulmonary disease
  • diary data
  • event history analysis
  • exacerbation
  • health process
  • logistic regression
  • medication
  • score function
  • symptoms
  • COPD epidemiology
  • COPD exacerbations
  • COPD pharmacology
  • cystic fibrosis
  • COPD epidemiology
  • COPD pathology
  • lung physiology
  • bronchiectasis
  • COPD mechanisms

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  • Funding The London COPD Cohort is funded by The Medical Research Council, UK. Financial help for this research was provided by a Development Research Award from the Department of Medicine of the University of Ottawa to SDA and GAW.

  • Competing interests None.

  • Patient consent Obtained.

  • Ethics approval Ethics approval was obtained from East London and the City and Royal Free Hospital research ethics committees. All patients provided written informed consent.

  • Provenance and peer review Not commissioned; externally peer reviewed.

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