Unreported and Overlooked: A Post Hoc Analysis of COPD Symptom-Related Attacks from the RISE Study

Moderate and severe COPD exacerbations are a significant health-care burden, but patients also experience "mild" exacerbations, or COPD symptom-related attacks, which often go unreported. We aimed to define and then determine the incidence of COPD symptom-related attacks and their impact on future risk of moderate/severe exacerbations, health-related quality of life (HRQoL), and lung function. The effect of COPD maintenance therapy on the attack definition was then evaluated by comparing budesonide/formoterol with formoterol alone.

This post hoc analysis of the RISE study defined COPD symptom-related attacks as ≥2 consecutive days of both worsening symptoms and increased daily rescue medication use based upon thresholds of >2 and >4 short-acting β₂-agonist (SABA) inhalations/day above baseline. The impact of these events on subsequent moderate/severe exacerbation risk was estimated using a time-varying Cox proportional hazards model. The effects of COPD symptom-related attacks on St George's Respiratory Questionnaire (SGRQ) total score and pre-bronchodilator forced expiratory volume in 1 second (FEV₁) were evaluated as average changes from baseline to first post-attack measurement. Rates of attacks were compared between treatment groups using negative binomial regression models.

COPD symptom-related attacks elevated the risk of subsequent moderate/severe exacerbations at both >2 and >4 inhalations/day above baseline (HR 1.86 and 2.21, respectively; p<0.0001), with a cumulative increase in risk with increasing attacks. HRQoL and lung function were reduced for patients with ≥1 versus no COPD symptom-related attacks at both rescue medication thresholds. There were fewer COPD symptom-related attacks with budesonide/formoterol versus formoterol alone, with no increased risk of pneumonia and lower respiratory tract infections.

COPD symptom-related attacks are common and typically unreported. Importantly, these attacks can account for considerable morbidity and should not be regarded as "mild". Detection of such exacerbations may be valuable in identifying patients at greater risk and guiding preventive therapeutic interventions.