Symptom variability in COPD: a narrative review

Chronic obstructive pulmonary disease (COPD) has traditionally been considered an inexorably progressive disease, associated with a constant increase of symptoms that occur as the forced expiratory volume in 1 second (FEV1) worsens, only intermittently interrupted by exacerbations. However, this paradigm has been challenged in recent decades by the available evidence. Recent studies have pointed out that COPD-related symptoms are not consistently perceived by patients in the same way, showing not only seasonal variation, but also changes in symptom perception during a week or even within a single day. According to the available data, patients experience the biggest increase in respiratory symptoms during the first hours of the early morning, followed by the nighttime. This variation over time is of considerable importance, since it impacts on daily life activities and health-related quality of life, as measured by a recently developed ad hoc questionnaire. Additionally, recent clinical trials have suggested that the use of rapid-onset long-acting bronchodilators may have an impact on morning symptoms, despite their current use as maintenance treatment for a determined period. Although this hypothesis is to be validated in future long-term clinical trials comparing fast-onset versus slow-onset inhaled drugs in COPD, it may bring forward a new concept of long-term bronchodilator therapy. At the present time, the two available long-acting, fast-onset bronchodilators used in the treatment of COPD are formoterol and the recently marketed indacaterol. Newer drugs have also been shown to have a rapid onset of action in preclinical studies. Health care professionals caring for COPD patients should consider this variation in the perception of symptoms during their clinical interview as a potential new target in the long-term treatment plan.