1. INTRODUCTION
Asthma affects 5–10% of the population and contributes to approximately 0.4 million deaths annually worldwide1. Asthma causes a high global burden of death and disability and is in the top 20 causes of years of life lived with disability. Although the mortality in asthmatic patients has decreased, asthma still has a sizable health-related burden of life2,3.
Asthmatic patients are generally considered to have higher mortality than subjects without asthma4-6. In a large population-based matched cohort study, the mortality in asthmatics was higher than in controls4. Another study reported similar results using a provincial health database6. However, in most countries, it remains inconclusive which factors cause higher mortality in patients with asthma compared with subjects without asthma because of the lack of evaluation of this issue using a nationally representative database4,6.
Respiratory conditions including chronic obstructive pulmonary disease (COPD), bronchiectasis, lung cancer, pneumonia, and non-tuberculous mycobacteria (NTM) infection are important comorbidities that affect the natural course of asthma. Coexisting COPD is associated with poor asthma control and increased healthcare use and is an important risk factor for mortality in patients with asthma4,6. However, except for COPD, the association of these comorbidities and mortality in patients with asthma has not been well elucidated, although the comorbid conditions have potential deteriorating effects of asthma on mortality. For example, bronchiectasis is associated with the severity of asthma7, and asthmatic patients are at increased risk of serious diseases, such as lung cancer8 and pulmonary infectious conditions (e.g., pneumonia and NTM infection)9,10, which can result in increased mortality in patients with asthma.
Thus, this study aimed to compare the mortality rate in patients with and without asthma using a representative nationwide database. We also evaluated the effects of asthma-related respiratory comorbidities on mortality in patients with asthma compared with subjects without asthma.