Prevalence of asthma–COPD overlap syndrome among primary care asthmatics with a smoking history: a cross-sectional study

Abstract

Background:The overlap between asthma and chronic obstructive pulmonary disease (COPD) is an important clinical phenomenon. However, the prevalence of asthma–COPD overlap syndrome (ACOS) is not known.Aims:To investigate the prevalence of ACOS among asthmatic patients with a smoking history, and evaluate the factors predicting ACOS in this patient group.Methods:We investigated 190 primary care asthma patients with no previous diagnosis of COPD, but who were either current or ex-smokers, with a smoking history of at least 10 pack-years. Spirometry was performed on all the patients while they were taking their normal asthma medication. Patients were considered to have ACOS if their postbronchodilator forced expiratory volume in 1 s/forced vital capacity was <0.70.Results:Fifty-two (27.4%) of the patients were found to have ACOS. Age ⩾60 years and smoking for ⩾20 pack-years were the best predictors of ACOS. If both of these criteria were met, the odds ratio (95% confidence interval) for ACOS was 6.08 (2.11–17.49), compared with the situation where neither of these criteria were fulfilled.Conclusions:There is a high prevalence of ACOS among primary health care asthmatics with a positive smoking history but no previous diagnosis of COPD. In this population, age over 60 years and a smoking history of more than 20 pack-years were the best predictors of ACOS.

Asthma–Chronic Obstructive Pulmonary Disease Overlap Syndrome

“…Age over 60 and higher burden of smoking history (over 20 pack-years) were associated with being part of the overlap group in this study. (16) A similar study of 256 Korean patients with asthma (defined by bronchodilator reversibility or positive methacholine challenge) found that 38% had incompletely reversible airflow obstruction on two separate occasions at least 3 months apart. This group was noted to be older, higher proportion male, and have more current and former smokers than the group with asthma alone.…”

“…(8) The estimated prevalence of the syndrome appears to vary based upon the population studied and the definitions utilized to describe the syndrome, but has been estimated between 13% and 38% of the population with obstructive lung disease. (9–21) Most estimates of prevalence of ACOS among a population of individuals with asthma appears to be slightly higher, with estimates ranging 27.1%–38%(13, 16, 18), whereas estimates of ACOS within a population of individuals with COPD appear to be slightly lower, ranging mostly from 13%–28.6%. (9–11, 14, 17, 19–21) Other than the differences in population characteristics which may account for the variation in prevalence estimates, the definitions utilized to identify individuals with ACOS also differ greatly.…”

Smoking asthma phenotype

“…In a cross-sectional study in primary care investigating the prevalence of ACOS among asthmatic patients with a smoking history of at least 10 pack-years almost 25% were considered as having ACOS. In this study age over 60 years and a smoking history of more than 20 pack-years were the best predictors of ACOS [16].…”

Asthma COPD overlap syndrome (ACOS)

“…A study by Kiljander et al revealed ACOS prevalence as 27.4% in asthma patients who have a history of smoking. Smoking 20 pack years and age over 60 years were best predictors of ACOS in the study population and these risk factors together increase ACOS risk 6 fold (p: 0.001) [16]. The reason suggested to explain high ACOS prevalence is that asthma and airway hyperresponsiveness to be among the COPD risk factors.…”