[A study on yearly and daily circadian rhythm of cardiovascular events].

Objective: To investigate the circadian and seasonal distribution of cardiovascular events (CVE) and the relationship between average monthly temperature and the incidence of CVE.

Methods: A total of 5837 emergency patients with CVE were enrolled from 1997 to 2007. The exact admission time of each patient was registered. The average monthly temperature data from a regional weather station for this time period was supplied by the meteorological office of the city. The relationship between the average monthly temperature and the incidence of CVE was explored and the corresponding curves were plotted.

Results: The occurrence of CVE has obvious seasonal variation, and its a higher tendency of episodes was found in spring and winter periods. High incidence of acute myocardial infarction, angina pectoris, acute left-sided heart failure, hypertensive crisis, and sudden death occurred in spring and winter as well as the time for a change of season, that is, January, February, March, April, October, November, and December. There was a significant negative correlation between the incidence and the average monthly temperature (P < 0.005 - 0.001). Circadian rhythm of CVE was present, with a peak in the early morning and forenoon.

Conclusion: There are circadian and circadian rhythms of the incidence of CVE. Cold weather condition is a risk factor for the occurrence of CVE, which usually peaks in the early morning and forenoon.