Abstract:

Objective To exploring the impact of extreme temperatures on the mortality risk of acute myocardial infarction（AMI） in Chengdu City，and provide scientific methods for climate adaptation policies and personalized protection for sensitive populations. Methods Data on daily meteorology，air pollutant monitoring and AMI mortality were collected in Chengdu City from 2020 to 2024. Apply a distributed lag non-linear model（DLNM） to estimate relative risk（RR） and cumulative relative risk（CRR） of extreme temperatures on AMI mortality，and conduct stratified analysis by gender and age to explore the sensitivity of different populations to extreme temperatures. Results From 2020 to 2024，the number of deaths due to AMI in Chengdu City was 32 295. The distribution relationship between daily average temperature and AMI mortality in Chengdu City showed an approximately "V" exposure-response curve. When the average daily temperature was 23 ℃，the risk of AMI mortality was the lowest. The single-day effect of extreme low temperature on AMI mortality risk followed an "S" shaped curve，with harmful effects emerging from lag 2 and peaking at lag 14，with an RR（95%CI） of 1.18（1.08-1.29）. The cumulative effect also reached its maximum at lag 14，with a CRR（95%CI） of 2.25（1.72-2.93）. The single-day effect of extreme high temperature on AMI mortality risk was strongest on lag 0，with an RR（95%CI） of 1.13（1.06-1.20），then gradually declined and persisted until lag 8. The cumulative effect peaked at lag 11，with a CRR（95%CI） of 1.59（1.42-1.78）. Subgroup analysis revealed that the CRR for extreme low temperature was higher in females than males，with CRR（95%CI） of 2.55（1.73-3.75） and 1.23（1.11-1.36），respectively. The effect on AMI mortality risk was not statistically significant for individuals aged 0-<61 years old，while for those aged ≥61 years old，the cumulative effect peaked at lag 14，with a CRR（95%CI） of 2.36（1.78-3.15）. For extreme high temperature，the peak cumulative effect occurred earlier in females（lag 9） than males（lag 14），with CRR（95%CI） of 1.75（1.56-1.96） and 1.49（1.24-1.78），respectively. Both the 0-<61 years age group and ≥61 years age group reached their maximum cumulative effects at lag11，but the CRR of the ≥61 years age group was higher than that of the 0-<61 years age group，with CRR（95%CI） of 1.65（1.46-1.86） and 1.34（1.08-1.67），respectively. Conclusion Extreme temperatures are associated with increased mortality risk from AMI，with a delayed but sustained effect for extreme low temperature and an immediate but transient effect for extreme high temperature. Females and individuals aged ≥61 years old were vulnerable subgroups.

Key words: Extreme temperatures, Acute myocardial infarction, Distributed lag non-linear model, Mortality risk, Relative risk, Cumulative relative risk