Patients with asthma were found to have a more than 3-fold greater risk of developing narcolepsy than those without asthma, with use of inhaled corticosteroids indicated to decrease risk.
In assessing the pathophysiology of narcolepsy, its impact on early rapid-eye movement sleep and fragmented sleep has been shown to cause irregular respiratory responses and result in breathing disorders, such as asthma. Moreover, narcolepsy and asthma have been considered to share common immunopathological mechanisms, with prior studies indicating that allergic disorders were associated with both type 1 and type 2 narcolepsy development.
“Although variables associated with delayed narcolepsy diagnosis have been identified, a lack of symptom recognition and comorbidities can result in misdiagnosis prior to the final narcolepsy diagnosis,” they noted. “A previous review reported a delayed diagnosis of narcolepsy by up to 15 years.”
Seeking to further confirm associations between asthma and narcolepsy, researchers conducted a nationwide population-based, nested case-control study of data derived from Taiwan’s National Health Insurance Research Database between 2000 and 2013. Enrolled patients with narcolepsy (n = 502) were compared 1:3 with propensity score-matched controls (n = 1506) based on sex, age, and index year.
The primary end point of the association between narcolepsy and asthma was evaluated via multiple logistic regression analyses, with several covariates accounted for, including 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 the central nervous system.
The researchers additionally examined the effects of corticosteroid and bronchodilator use on the association between asthma and narcolepsy. Compared with controls, patients with narcolepsy had almost 3 times the level of previous asthma diagnoses, as well as a greater incidence of psychiatric disorders, obstructive sleep apnea, and inhaled/oral/injected corticosteroid use.
According to findings of the multivariate logistic regression analysis, patients with narcolepsy had a risk for narcolepsy comorbidity that was more than 3 times that of controls (adjusted OR [aOR], 3.181; 95% CI, 2.048-4.941; P < .001).
Notably, use of inhaled corticosteroids was associated with an approximate 53% reduction in risk of narcolepsy comorbidity in patients with asthma vs those without treatment (aOR, 0.465; 95% CI, 0.250-0.634; P < .001). No significant difference was observed for the bronchodilator-only group among the patients with asthma.
Speaking on the study findings, the researchers said that limitations included the lack of knowledge regarding which type of narcolepsy, 1 or 2, enrolled patients had, as well as not accounting for factors that could have influenced results, such as coffee consumption and smoking.
They concluded that clinicians should be aware of the possibility of narcolepsy following a diagnosis of asthma and that further research is warranted to explore the underlying mechanisms of the 2 diseases.
Chen T-Y, Su VY-F, Lee C-H, et al. The association between asthma and narcolepsy: a nationwide case-control study in Taiwan. Nat Sci Sleep. 2021;13:1631-1640. doi:10.2147/NSS.S317746