Researchers Find More Information on COPD–Asthma Overlap Syndrome Characteristics

Asthma—chronic obstructive pulmonary disease (COPD) overlap syndrome is a disease where features of both conditions are mixed. In a new study, researchers sought to identify the heterogeneity of asthma and COPD overlap syndrome, known as ACOS, in patients with mild to moderate airflow restriction. Using national survey and insurance claims data in Korea, they sought to identify the diverse epidemiological characteristics and subtypes of ACOS associated with exac­erbations, healthcare use, and cost.

Researchers included subjects from the Korean National Health and Nutrition Examination Survey between 2007 and 2012 if they met the criteria of being 40 years or older and having prebronchodilator forced expiratory volume in 1 second (FEV₁)/forced vital capacity (FVC) of less than 0.7 and FEV₁ of at least 50% predicted.

Presence or absence of self-reported wheezing was indicated by W+ or W− and was used as an index of airway hyperresponsiveness. Smoking was indicated by S+ (smokers) or S− (never smoked). The subjects were divided into the following 4 groups: W−/S−; W−/S+; W+/S−; and W+/S+.

Of the 2269 subjects, 410 (18%) with W+ were classified with ACOS. Among those 410 subjects, 154 never-smokers were classified as W+/S− (asthma-predominant ACOS) and 256 smokers were classified as W+/S+ (COPD-predominant ACOS).

Of those without wheezing (W−), 681 were never smokers (W−/S−) and 1178 were smokers (W−/S+). Although mean age was not different, age distribution was significantly different among the 4 groups (P = .001).

Participants aged 40 to 50 years were more frequent in the W+ groups and those 50 to 70 years were more frequent in the S+ groups.

Men were more prevalent in both S+ groups than in both S− groups and in the COPD-predominant ACOS group than in the asthma-predominant ACOS group (both P <.001).

Body mass index and waist circumference were the highest in the COPD-predominant ACOS group (both P <.001). Household income and education level were the highest in the W−/S− group among the 4 groups (P <.001) and were lower in the asthma-predominant ACOS group than in the COPD-predominant ACOS group (P <.001).

The asthma-predominant ACOS group (W+/S−) showed the lowest levels of socioeconomic status, FEV₁, FVC% predicted, and quality of life.

The COPD-predominant ACOS group (W+/S+) showed the highest hospitalization rate and outpatient medical cost, as well as more frequent exacerbations and total and outpatient healthcare utilization.

COPD-predominant ACOS was associated with exacerbations compared with the W−/S− group (adjusted odds ratio, 1.79; 95% CI, 1.12-2.85; P = .015) and W−/S+ group (odds ratio, 2.11; 95% CI, 1.43-3.10; P <.001). It was also associated with increased medical cost.

The researchers said that the results show that it is beneficial to identify subtypes of patients with ACOS and appropriately allocate limited medical resources.

Reference

Kim MH, Rhee CK, Kim KJ, et al. Heterogeneity of asthma and COPD overlap. Int J Chron Obstruct Pulmon Dis. 2018:13;1251-1260. doi: 10.2147/COPD.S152916.