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

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.

Our retrospective registry including all patients who died in the Cardiology Department, including the cardiac intensive care unit, Madrid, Spain.

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.

Mortality in hospitalized patients with cardiovascular diseases follows a circadian biphasic pattern.