Circadian Rhythm of Deaths in a Cardiology Department: A Five-Year Analysis

Abstract

Background: Previous studies have described a circadian pattern of death from cardiovascular causes with a morning peak. Our aim is to describe the daytime oscillations in mortality in hospitalized patients with cardiovascular diseases. Methods: Our retrospective registry including all patients who died in the Cardiology Department, including the cardiac intensive care unit, Madrid, Spain. Results: From a total of 500 patients, time of death was registered in 373 (74.6%), which are the focus of our study; 354 (70.8%) died in the cardiac intensive care unit and 146 (29.2%) in the conventional ward. Mean age was 74.2 ± 13.1 years, and 239 (64.1%) were male. Cardiovascular causes were the leading cause of death (308 patients; 82.6%). Mortality followed a circadian biphasic pattern with a peak at dawn (00.00–05.59 a.m.: 104 patients [27.9%]) and in the afternoon (12.00–17.59 p.m.: 135 patients [36.2%]), irrespective of the cause of death. The peak of mortality occurred in the afternoon (12.00–17.59 p.m.) in the case of cardiovascular mortality (119 deaths [38.6%]) and in the evening (18.00–23.59 p.m.) for non-cardiovascular deaths (21 deaths [32.3%], p = 0.03). This pattern was present regardless from the place of death (conventional ward or cardiac intensive care unit) and also throughout the four seasons. Conclusions: Mortality in hospitalized patients with cardiovascular diseases follows a circadian biphasic pattern.