Bidirectional effect modification between diurnal temperature range and particulate matter on acute myocardial infarction risk.

Both ambient particulate matter and temperature variability influence acute myocardial infarction (AMI) risk. However, epidemiological evidence on whether diurnal temperature range (DTR) and particulate matter mutually modify each other's cardiovascular effects remains limited. We conducted a time-stratified case-crossover study including 149,632 AMI hospitalizations in Beijing, China, from 2013 to 2019. Our results showed that short-term exposure to PM2.5 and PM10 increased AMI hospitalization risk, while DTR had a nonlinear U-shaped association, with higher risks at both low and high DTR levels. Interaction analysis revealed that the effect of PM2.5 was stronger under low DTR, while the impact of PM10 was more significant under medium to high DTR. The effect of DTR was amplified at lower levels of particulate matter but diminished at higher pollution levels. These findings highlight the importance of incorporating both temperature variability and air pollution into cardiovascular risk assessments and early warning systems.