Temporal and demographic variation in the association between short-term PM2.5 exposure and suicide mortality in Bangkok, Thailand

Thailand experiences consistently high concentrations of ambient fine particulate matter (PM 2.5 ), with Bangkok frequently exceeding national ambient air quality standard and posing a major public health concern. While suicide represents an important cause of mortality in Thailand, evidence on the short-term association between PM 2.5 exposure and suicide mortality in this highly polluted urban setting remains limited. This study aimed to investigate the association between short-term PM 2.5 exposure and suicide mortality in Bangkok, Thailand using data from 2020 to 2023, and to explore temporal and demographic variation in this association by sex and age. We applied a time-stratified case-crossover design with conditional logistic regression to estimate short-term association and included interaction terms between PM 2.5 and calendar year to examine how this association may change over time. We found that short-term exposure to PM 2.5 was associated with an increased risk of suicide mortality. Significant positive associations were observed for females and non-elderly individuals (<60 years) at lag 3-day, and for the elderly (≥60 years) at lag 2-day. In addition, the temporal changes in this association were observed with stronger associations in later years, particularly in 2023. These changes were statistically significant ( p -value for interaction <0.05) for both the non-elderly and elderly groups. Our findings suggest that estimated risk of suicide mortality associated with PM 2.5 exposure changed over time, indicating that temporal changes in population vulnerability or exposure may influence risk and highlighting the importance of integrating temporal risk patterns into public health planning and prevention strategies.