Associations of ambient temperature and PM2.5 concentration with temporal variability in emergency department visits for acute gastrointestinal illnesses in central Bangkok, Thailand: a 5-year retrospective analysis

Abstract

The combined effects of temperature and air pollution on acute gastrointestinal (GI) illnesses remain underexplored in tropical settings. This study examined the association between ambient temperature, fine particulate matter (PM2.5), and emergency department (ED) visits for gastritis and gastroenteritis in Bangkok, Thailand. We conducted a retrospective analysis of ED visits from 2018 to 2023 at a large urban hospital in Bangkok, Thailand. The effects of heat index (HI) levels and daily PM2.5 were assessed using generalized additive and distributed lag non-linear models, with stratified analyses to explore interaction effects. Higher HI and PM2.5 levels were associated with increased acute GI-related ED visits. PM2.5 concentrations exceeding 139.8 µg/m³ were associated with elevated risk compared with the mean daily level. Conversely, HI below 30 °C was linked with a lower cumulative risk. Stratified models suggested that extreme heat may exacerbate the adverse impact of elevated PM2.5. In the urban setting of Thailand, very high PM2.5 (> 139.8 µg/m³) may be associated with increased patients presenting to the ED with acute GI illnesses. The risk of increased patient counts appeared to be higher with greater PM exposure, particularly when elevated PM levels coincided with a high heat index, whereas cooler conditions appeared protective. These findings highlight the need for further investigation of interactive environmental exposures to inform public health and adapt the ED management strategies.