The Association Between Asthma and Narcolepsy: A Nationwide Case-Control Study in Taiwan

PURPOSE: Asthma, which is caused by inflammation of the airways, affects the sensitivity of nerve endings. Narcolepsy is a chronic sleep disorder that may be caused by autoimmunity. Recent studies have reported a positive association between narcolepsy and asthma. We aimed to examine the association between asthma and narcolepsy and determine the effects of therapeutic corticosteroid or bronchodilator use. MATERIALS AND METHODS: We conducted a nationwide population-based, nested case-control study using Taiwan’s National Health Insurance Research Database (NHIRD) between 2000 and 2013. Subjects with narcolepsy (ICD-9-CM code 347) were enrolled, with 1:3 estimated propensity score-matched controls based on sex, age, and index year. The association between narcolepsy and asthma was assessed using multiple logistic regression analyses. The covariates included sex, age, monthly insurance premiums, geographical area of residence, urbanization level of residence, level of care, and presence of diseases related to immune response and central nervous system. The effects of corticosteroid and bronchodilator use were also analyzed. RESULTS: Overall, 2008 subjects were identified from the NHIRD (502 patients with narcolepsy and 1506 controls). The participants with narcolepsy had almost three times the level of previous asthma diagnosis than controls. Compared to those without asthma, patients with asthma had an adjusted odds ratio (OR) of 3.181 for narcolepsy comorbidity (95% confidence interval [CI]: 2.048–4.941, p<0.001). The use of inhaled corticosteroids was associated with a lower risk of narcolepsy comorbidity, with an adjusted OR of 0.465 (95% CI, 0.250–0.634; p<0.001), in patients with asthma when compared to those without treatment. CONCLUSION: This study demonstrated a significantly higher level of previous asthma diagnosis in patients with narcolepsy. The use of inhaled corticosteroids was associated with a lower risk of narcolepsy comorbidity in asthma patients, compared to those without treatment.