Association between nocturnal asthma, symptom severity, and clinical outcomes: a systematic review

OBJECTIVE: Nocturnal asthma is characterized by the worsening of asthma symptoms during the night and indicates more severe disease. This review aims to analyze evidence regarding the association between nocturnal asthma, symptom severity, pulmonary function, and clinical outcomes in both adult and pediatric populations. METHODS: Databases Embase, PubMed, CINAHL, Cochrane (Wiley), Scopus, and LILACS were searched from their dates of inception to April 8, 2024. We included studies comparing severity of asthma symptoms, pulmonary function, and clinical outcomes in patients with nocturnal asthma to patients with nocturnal asthma. RESULTS: Thirteen studies met the inclusion criteria for this review. These studies varied in setting, population, definitions of nocturnal, and outcome assessment. Despite methodological heterogeneity, a consistent pattern emerged: none of the evaluated outcomes had better results in the nocturnal asthma group, and nocturnal asthma was associated with worse symptom severity and poorer pulmonary function in most studies. However, evidence regarding hospital outcomes was mixed, with only one study reporting increased ward or intensive care unit (ICU) admission rates for nocturnal asthma patients, and no differences observed in length of stay. CONCLUSIONS: Evidence presented in this systematic review reinforced the association between nocturnal asthma and more severe disease manifestations, including worse symptom scores and poorer pulmonary function compared to non-nocturnal asthma. While evidence regarding hospitalization outcomes remains inconclusive, the findings underscore the clinical significance of recognizing nocturnal symptoms to improve disease management and diagnosis.