Effect of temperature fluctuations in cold seasons on acute myocardial infarction hospitalisations in northeast China: a retrospective observational cohort study

OBJECTIVE: This study aimed to determine the potential influence of ambient temperature on the incidence of acute myocardial infarction (AMI). DESIGN: A retrospective observational cohort study. SETTING: Changchun, a northeastern city in China, has a temperate continental humid climate. PARTICIPANTS: 1933 AMI patients admitted to the outpatient department of the First Hospital of Jilin University were included in the study from 1 January 2017 to 31 December 2019. OUTCOME MEASURE: We explored the effect of daily minimum and maximum temperatures, as well as temperature changes on two adjacent days, on the incidence of daily AMI from 1 to 5 days later in Changchun. RESULTS: We found that the average daily number of AMI cases was higher from October to April in cold season compared with the period between May and September in warm season. When the daily maximum temperature is ≤−6°C on the −2nd day, the incidence of AMI>3 persons more than doubled (from 8.51% and 10.88% to 20.23%) in the next 2 days (p=0.027); and more than 65% of the days had a maximum temperature fluctuation on |(−2nd day) − (−3rd day)| ≥2°C in these days, the OR of the daily incidence of AMI>3 persons is 3.107 (p=0.018); and in these days with enhanced temperature fluctuations, the proportion of AMI patients with hypertension had increased significantly from 20.83% to 45.39% (p=0.023). CONCLUSION: Ambient temperature as environmental factor has a seasonal effect on the incidence of AMI in temperate continental humid climate regions, with a 2–3 days lag. Furthermore, the key factor contributing to the increase in the daily incidence of AMI during the cold season is temperature fluctuations, and maintaining a constant temperature may aid in preventing the occurrence of AMI. TRIAL REGISTRATION NUMBER: ChiCTR2300068294.