Short-term effects of ambient PM2.5 on respiratory healthcare utilisation in older adults: a time-series study in an industrialising area of Central Thailand.

BACKGROUND: Fine particulate matter (PM2.5) air pollution is a major environmental health concern and has been associated with adverse respiratory outcomes, particularly among older adults. Evidence regarding the short-term respiratory effects of PM2.5 in communities near newly industrialising areas in Thailand remains limited. We aimed to examine the short-term association between daily ambient PM2.5 concentrations and respiratory healthcare utilisation among older adults living near a newly established industrial area in central Thailand. METHODS: We conducted a time-series study among residents aged ≥60 years living within a 5 km radius of an industrial area in central Thailand from November 2023 to March 2024. Daily respiratory healthcare visits (ICD-10 codes J00-J99) were obtained from electronic medical records of the local secondary-level hospital. We obtained daily PM2.5 concentrations and meteorological data from the nearest governmental air-quality monitoring station. Associations between PM2.5 exposure and respiratory visits were analysed using negative binomial regression models and expressed as incidence rate ratios (IRRs) per 10 μg/m3 increase in PM2.5. We used single-lag and moving-average models to assess delayed effects, adjusting for temperature, relative humidity, wind speed, day of the week, and temporal trends. RESULTS: A total of 924 respiratory healthcare visits were recorded during the study period, with a mean of 6.37 visits per day. The mean daily PM2.5 concentration was 42.43 μg/m3 (standard deviation = 15.12), substantially exceeding the World Health Organization guideline. Positive associations between PM2.5 and respiratory visits were observed across several lag days, with the largest effect estimate at lag 4. A 10 μg/m3 increase in PM2.5 at lag 4 was associated with a 5.5% increase in respiratory healthcare visits (IRR = 1.055, 95% confidence interval = 0.995-1.119), although this association did not reach statistical significance. Subgroup analyses showed numerically larger effect estimates among females and individuals aged 60-69 years; however, interaction tests were not statistically significant. CONCLUSIONS: Short-term exposure to ambient PM2.5 showed a positive but non-significant association with respiratory healthcare utilisation among older adults living near a newly industrialising area. Continued efforts to improve air quality and protect vulnerable populations may help reduce pollution-related respiratory health burdens.