Time series analysis of environmental factors and their association with emergency visits for asthma exacerbations in Petaling Jaya, Malaysia.

BACKGROUND

The burden of respiratory conditions, especially asthma, is likely to increase with urbanisation and pollution unless effectively managed. Petaling Jaya, a metropolitan area, faced heightened risk due to worsening outdoor air pollution, which can trigger asthma exacerbations. We aimed to examine the relationships between environmental factors and emergency visits for asthma exacerbations.

METHODS

We used retrospective data over four years (1 January 2014 to 13 April 2017) comprising clinical records from a main hospital in Klang Valley and environmental data (air pollutants and meteorological data) obtained from nearby stations. We used generalised additive models to assess the associations between environmental factors and asthma emergency visits. We used distributed lag nonlinear models to address the delayed effects and nonlinearity of particulate matter at 10 μm (PM10) exposure on these visits.

RESULTS

Asthma exacerbations accounted for 2.3% of total emergency visits. Daily mean (x̄) PM10 level exceeding Malaysian Ambient Air Quality Standard (MAAQS) threshold was associated with a 21.3% (95% confidence interval (CI) = 2.2, 44.0) increase when levels reached 200 μg/m3 and 34.0% (95% CI = 4.7, 71.7) increase when levels reached 300 μg/m3 in asthma emergency visits. The lag effect was associated with PM10 exposure levels, peaking on days two and three at 100 μg/m3 and on the same day at 200 μg/m3 and 250 μg/m3. The cumulative exposure-response curve from lag 0-7 days shows that the increased relative risk of asthma emergency visits began at PM10 levels of 150 μg/m3.

CONCLUSIONS

We provide preliminary insights into the respiratory health burden in the Klang Valley. The associations observed between PM10 and asthma emergency visits are exploratory. Our findings suggest that the risk of visits may increase when PM10 levels near or above current MAAQS thresholds, highlighting the potential benefit of aligning local air quality standards with stricter international guidelines. These results may support the value of targeted preventive measures and healthcare resource planning for asthma, though larger multi-year data sets are required to enhance statistical robustness.