Exacerbation-like respiratory symptoms in individuals without chronic obstructive pulmonary disease: results from a population-based study

Abstract

Rationale: Exacerbations of COPD are defined clinically by worsening of chronic respiratory symptoms. Chronic respiratory symptoms are common in the general population. There are no data on the frequency of exacerbation-like events in individuals without spirometric evidence of COPD.

Aims: To determine the occurrence of 'exacerbation-like' events in individuals without airflow limitation, their associated risk factors, healthcare utilisation and social impacts.

Method: We analysed the cross-sectional data from 5176 people aged 40 years and older who participated in a multisite, population-based study on lung health. The study cohort was stratified into spirometrically defined COPD (post-bronchodilator FEV1/FVC < 0.7) and non-COPD (post bronchodilator FEV1/FVC ≥ 0.7 and without self-reported doctor diagnosis of airway diseases) subgroups and then into those with and without respiratory 'exacerbation-like' events in the past year.

Results: Individuals without COPD had half the frequency of 'exacerbation-like' events compared with those with COPD. In the non-COPD group, the independent associations with 'exacerbations' included female gender, presence of wheezing, the use of respiratory medications and self-perceived poor health. In the non-COPD group, those with exacerbations were more likely than those without exacerbations to have poorer health-related quality of life (12-item Short-Form Health Survey), miss social activities (58.5% vs 18.8%), miss work for income (41.5% vs 17.3%) and miss housework (55.6% vs 16.5%), p<0.01 to <0.0001.

Conclusions: Events similar to exacerbations of COPD can occur in individuals without COPD or asthma and are associated with significant health and socioeconomic outcomes. They increase the respiratory burden in the community and may contribute to the false-positive diagnosis of asthma or COPD.

Keywords: Asthma Epidemiology; COPD Exacerbations; Clinical Epidemiology.

Figure 1

Frequency distribution of proportion of people in non-COPD and COPD groups with exacerbation in the past 1 year (DDX A/C: self-reported doctor's diagnosis of asthma/emphysema/chronic bronchitis/COPD).

Figure 2

Frequency of chronic respiratory symptoms in 3379 subjects without COPD with and without exacerbation in the past 1 year. Non COPD=subgroup with post-bronchodilator FEV₁/FVC<0.7 and no self-reported doctor's diagnosis of asthma/emphysema/chronic bronchitis/COPD. Open columns=no exacerbation in the past 1 year; closed columns=exacerbation in the past 1 year.

Figure 3

Predictors of exacerbation in the past 1 year in two subgroups of subjects: COPD (post-bronchodilator FEV₁/FVC<0.7) and non-COPD (post-bronchodilator FEV₁/FVC<0.7 and no self-reported doctor's diagnosis of asthma/emphysema/chronic bronchitis/COPD). # For the non-COPD subgroup, the OR for each variable is adjusted for other variables in the figure as well as age, BMI, ever smoking, chronic cough, breathlessness, comorbidities, childhood hospitalisation for breathing problem, and for bronchodilator response after salbutamol (% change in FEV₁ and % change in FVC.) For the COPD subgroup, additional adjustment included self-reported DDX of asthma, self-reported DDX of emphysema/CB/COPD. Open circles=non-COPD; closed circles=COPD. *Significance is assumed at p value<0.05. SHS, self-perceived health status.

Figure 4

Impact on health-related quality of life ( expressed as physical component scores and mental component scores computed from SF12) in 3379 Non COPD subjects with and without exacerbation in the past 1 year. Non COPD=subgroup with post-bronchodilator FEV1/FVC <0.7 and no self-reported doctor diagnosis of asthma/emphysema/chronic bronchitis/COPD. Open columns=no exacerbation in the past 1 year; closed columns=exacerbation in the past 1 year.

Figure 5

Impact on missing work and missing social activities in the past year in 3379 Non COPD subjects with and without exacerbation in the past 1 year. Non COPD=subgroup with post-bronchodilator FEV1/FVC<0.7 and no self-reported doctor diagnosis of asthma/emphysema/chronic bronchitis/COPD. Open columns=no exacerbation in the past 1 year; closed columns=exacerbation in the past 1 year.