The coexistence of asthma and COPD: risk factors, clinical history and lung function trajectories

Abstract

Patients with concomitant features of asthma and chronic obstructive pulmonary disease (COPD) have a heavy disease burden.Using data collected prospectively in the European Community Respiratory Health Survey, we compared the risk factors, clinical history and lung function trajectories from early adulthood to late sixties of middle-aged subjects with asthma+COPD (n=179), past (n=263) or current (n=808) asthma alone, COPD alone (n=111) or none of these (n=3477).Interview data and pre-bronchodilator forced expiratory volume in 1 s (FEV₁) and forced vital capacity (FVC) were obtained during three clinical examinations in 1991-1993, 1999-2002 and 2010-2013. Disease status was classified in 2010-2013, when the subjects were aged 40-68 years, according to the presence of fixed airflow obstruction (post-bronchodilator FEV₁/FVC below the lower limit of normal), a lifetime history of asthma and cumulative exposure to tobacco or occupational inhalants. Previous lung function trajectories, clinical characteristics and risk factors of these phenotypes were estimated.Subjects with asthma+COPD reported maternal smoking (28.2%) and respiratory infections in childhood (19.1%) more frequently than subjects with COPD alone (20.9% and 14.0%, respectively). Subjects with asthma+COPD had an impairment of lung function at age 20 years that tracked over adulthood, and more than half of them had asthma onset in childhood. Subjects with COPD alone had the highest lifelong exposure to tobacco smoking and occupational inhalants, and they showed accelerated lung function decline during adult life.The coexistence between asthma and COPD seems to have its origins earlier in life compared to COPD alone. These findings suggest that prevention of this severe condition, which is typical at older ages, should start in childhood.

FIGURE 1

Study flowchart. ^#: subjects with post-bronchodilator forced expiratory volume in 1 s/forced vital capacity <lower limit of normal at European Community Respiratory Health Survey III who could not be classified in any of the disease groups (no Global Initiative for Chronic Obstructive Lung Diseases-defined indicators, no asthma history).

FIGURE 2

Predicted trajectories for the proportion of subjects reporting a) active smoking, b) passive smoking, c) dyspnoea or d) having been seen by a physician during the last 12 months as a function of disease group and age. Number of subjects contributing data=4838. p_interaction obtained by Wald test (null hypothesis: true trajectories do not vary by disease group). The vertical lines represent 95% confidence intervals. Quantitative/indicator independent variables were set equal to the mean/proportion calculated over the set of subjects included. p-values are for the test of significance of the age-related trend within a disease group (null hypothesis: true proportion is constant across ages). *: p<0.05; **: p<0.01; ***: p<0.001.

FIGURE 3

Predicted trajectories for mean pre-bronchodilator a) forced expiratory volume in 1 s (FEV₁), b) forced vital capacity (FVC) and c) FEV₁/FVC ratio as a function of disease group and age. Number of subjects contributing data=4831 (FEV₁), 4822 (FVC) and 4816 (FEV₁/FVC). p_interaction obtained by Wald test (null hypothesis: true trajectories do not vary by disease group). The vertical lines represent 95% confidence intervals. Spirometer type was set to NDD EasyOne; quantitative/indicator independent variables were set equal to the mean/proportion calculated over the set of subjects included. ***: p<0.001 for the test of significance of the age-related trend within a disease group (null hypothesis: true mean is constant across ages).