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.