An updated prevalence of asthma, its phenotypes, and the identification of the potential asthma risk factors among young Chinese adults recruited in Singapore

**Background:** Asthma is a chronic inflammatory airway disease affecting over 300 million people worldwide. Prevalence estimates have been changing over time, and updated data are needed, particularly in Asian populations. This study aimed to obtain an updated prevalence of asthma and its phenotypes and identify associated risk factors among young Chinese adults in Singapore.

**Methods:** Data were drawn from the Singapore/Malaysia Cross-Sectional Genetics Epidemiology Study (SMCGES), an ongoing cross-sectional study using established ISAAC guidelines. Participants were recruited from the National University of Singapore via email and poster advertisements since August 2005. The current analysis included 10,736 participants of Chinese ethnicity. Asthma status was determined by questionnaire: "ever asthma" (lifetime) and "current asthma" (symptoms within past 12 months). Atopy was assessed via skin prick test (SPT) for house dust mite allergens (Blomia tropicalis and Dermatophagoides pteronyssinus), with a wheal ≥3 mm considered positive. Epidemiological data included demographics, family history of allergic diseases, lifestyle factors (physical activity, TV/computer usage, smoking, alcohol, pet ownership), and dietary habits (16 food groups). Overall glycemic index (GI) was scored using the Quality of Diet based on Glycemic Index Score (QDGIS). Statistical analyses used simple and multiple logistic regression, reporting odds ratios (OR) and adjusted odds ratios (aOR) with 95% confidence intervals.

**Key Results:** Lifetime asthma prevalence was 19.1% (2049/10,736) and current asthma prevalence was 6.3% (679/10,736). Among ever asthma cases, 75.2% (1541/2049) were atopic, and 33.1% (679/2049) had current asthma. Among current asthma cases, 69.4% had wheeze-variant asthma, 60.7% had cough-variant asthma, and 30.1% had both. For ever asthma, the strongest risk factor was parental history of asthma (OR: 4.784, 95% CI: 4.038–5.670, p<0.001). Other significant factors included male gender (OR: 1.387, 95% CI: 1.255–1.532), being born in Singapore (aOR: 2.334, 95% CI: 2.020–2.706), higher income (≥SGD6000 vs <SGD2000, aOR: 1.558, 95% CI: 1.299–1.872), and history of drug allergy (aOR: 1.692, 95% CI: 1.419–2.012). Dietary factors associated with increased odds of ever asthma included cereals (aOR: 1.256, 95% CI: 1.006–1.580), pasta (aOR: 1.265, 95% CI: 1.027–1.553), butter (aOR: 1.350, 95% CI: 1.113–1.632), and margarine (aOR: 1.343, 95% CI: 1.081–1.660). Pulses (aOR: 0.822, 95% CI: 0.706–0.958) and probiotic drinks (aOR: 0.861, 95% CI: 0.756–0.980) were protective. Increased TV/computer usage (>5h vs <1h) was associated with reduced odds of ever asthma (aOR: 0.448, 95% CI: 0.367–0.545). For current asthma, genetic factors had weaker effects (parental asthma OR: 1.465, 95% CI: 1.135–1.888). Physical activity was protective (aOR: 0.693, 95% CI: 0.542–0.885), while second-hand smoke exposure increased risk (aOR: 1.435, 95% CI: 1.001–2.047). Only increased potato consumption was significantly associated with current asthma (most/all days vs never, aOR: 1.577, 95% CI: 1.145–2.180).

**Clinical Implications:** The higher-than-previously-reported asthma prevalence (19.1% lifetime, 6.3% current) among young Chinese adults in Singapore suggests a rising trend that warrants attention. The differential risk factor profiles for ever asthma (stronger genetic influence) versus current asthma (stronger lifestyle/environmental influence) suggest that interventions targeting modifiable factors—such as diet, physical activity, and second-hand smoke exposure—may be particularly effective in reducing active asthma symptoms. The protective association of pulses and probiotic drinks and the risk associated with high-GI foods like potatoes and cereals may inform dietary counseling. The strong association with parental asthma underscores the importance of family history screening for early identification of at-risk individuals.