Effect of low temperature on myocardial infarction mortality in rural residents: comparison of daytime and nighttime exposure.

Ambient low temperature is a risk factor for myocardial infarction (MI) worldwide, with limited evidence about the effect of low temperature at different periods of a day. We aimed to characterize the association of MI mortality with daytime and nighttime low temperatures in rural areas. Daily daily temperature data and MI deaths from 2016 to 2020 were obtained for the rural areas of Anhui Province. We first applied the distributed lag nonlinear model to examine the association of MI death risk with daily maximum (daytime) and minimum (nighttime) temperature for each rural area. Then, we used the random-effects meta-analysis to pool the rural-specific effect estimates and subgroups stratified by sex, age, and geographical region. Daytime low temperature and nighttime low temperature were both associated with an increased risk of MI death. On the same day of exposure to daytime low temperature and nighttime low temperature, the risk of MI death respectively increased by 12.6% [95% confidence interval (CI): 0.7% ~ 25.8%] and 3.2% (95%CI: 0% ~ 6.6%). Subgroup results showed an increased MI death risk associated with daytime and nighttime low temperatures in the elderly (≥ 65 years) and males. Besides, there was an obvious geographical variation in the lag effects of daytime and nighttime low temperatures on MI mortality. This study provides evidence of different effect of daytime and nighttime low temperature on MI mortality in China. Our findings may have important implications in preventing heart attacks during the day and at night in cold weather.
Competing Interests: Declarations. Ethics approval: The study was approved by the Ethics Committee of Anhui Medical University (approval number: 20210330). Informed consent was not required because the data were obtained and analyzed at the aggregated level. Competing interest: The authors have no competing interests to declare that are relevant to the content of this article.
(© 2025. The Author(s) under exclusive licence to International Society of Biometeorology.)