Ten-year longitudinal study of factors influencing nocturnal asthma symptoms among Asian patients in primary care

BACKGROUND: Nocturnal asthma symptoms result in poor quality of life and morbidity. AIMS: This study primarily examines key factors predicting and mitigating nocturnal symptom risks among asthma patients, who were enrolled into a Singapore publicly funded asthma care programme. It also studies the association between nocturnal symptoms and medication changes as the secondary outcome. METHODS: A longitudinal study was conducted on 939 multi-racial Asian patients with persistent asthma. Patient clinical and therapeutic data were retrieved retrospectively from the programme’s database established in 2004. Association between nocturnal symptoms (defined as night-time cough, wheeze and breathlessness at least twice monthly) and each categorical predictor was tested. The generalised linear mixed-effects model (GLIMM) was used to model the primary and secondary outcomes. RESULTS: Having nocturnal asthma symptoms was significantly associated with the number of days with breathlessness, off usual activities and off work, and asthma severity at baseline (all P values <0.05). The asthma action plan (AAP) status is significantly associated with nocturnal symptoms after adjusting for race, age and smoking status at baseline (odds ratio (OR)=0.49 (updated asthma action plan versus none), OR=0.37 (been-on plan versus none)). The risks of nocturnal asthma symptoms increased over time for those with allergic rhinitis (OR=1.52) and reduced with subsequent visits (OR=0.91). Nocturnal symptoms increased the odds (OR=2.87) of switching from inhaled corticosteroid (ICS) to combination medications (ICS-LABA (long-acting β(2)-agonist)). CONCLUSIONS: The risks of having nocturnal symptoms were primarily associated with those with allergic rhinitis. An increase in patients’ nocturnal symptoms was also predictive of the switching from ICS medications to combination formulations by their physicians.