The Spatio-temporal Epidemiology of Asthma Patient Visits in Relation to Meteorological Parameters and Air Pollution Factors as a Result of Seasonal Change in Songkhla Province

Objective: To investigate the demographic characteristics, seasonal variations, effects associated with air pollution, and geographic morbidity of asthma in Songkhla. Material and Methods: This research conducted a time series analysis of secondary data from 1 January, 2013 to 31 December, 2017. The distributed lag non-linear model was employed to analyze associations between air pollutants and daily asthma outpatient visits, and the Bayesian hierarchical modelling was used to map asthma morbidity spatiotemporally. Results: A total of 250,127 asthma diagnoses corresponding to 36,761 patients were found in the medical records. Most asthma outpatients were female (61.1%); males (1-5 years) constituted the majority of individuals during the first peak, while females (40-50 years) predominated the second peak. The trend analysis revealed a seasonal variation in the number of asthma outpatient visits; the highest rates were during the June-December period. The regression coefficient analysis revealed carbon monoxide (CO), nitrogen dioxide (NO2 ), relative humidity, and visibility to have the most significant positive effect on asthma, while the cos (wind direction) had the highest negative effect/impact. Significant associations were found between outpatient gender and age and CO, NO2 , sulfur dioxide, ozone, and particulate matter less than 10 micron. The Hat Yai and Central districts of Songkhla province were identified as morbidity hotspots. Conclusion: The number of asthma-related outpatient visits increased during the rainy season. Asthma affected primarily young boys and middle-aged women in this province, and they constitute the most sensitive group to air pollutants such as CO and NO2 and meteorological conditions like relative humidity and visibility. The highest morbidity rates were found in urbanized habitats.