Diurnal, weekly and seasonal variation of sudden death. Population-based analysis of 24,061 consecutive cases

Several studies have reported circadian and seasonal variations in acute cardiovascular disease. In addition, a weekly variation has been observed in acute myocardial infarction. The aim of our study was to determine the circadian weekly, and seasonal variations of sudden death utilizing population-based data.

We analysed the emergency medical system data of Berlin (West) from 1987-1991 with respect to all consecutive sudden deaths in subjects >18 years (n=24 061). There was a marked circadian variation of sudden death, with a minimum between 0 and 6 h and a maximum between 6 and 12 h (P<0.0001) for every day of the week. A minimum of events occurred on Sundays (n=3143), and a maximum on Mondays (n=3721), corresponding to a relative increase of 18.3% (P<0.0001). The increase was more pronounced (23.6%) in patients < or =65 than in patients >65 (15.7%). In addition, we found a significant seasonal variation (P<0.0001) in events, with a maximum during winter (December to February, n=6493), and a minimum during summer (June to August, n=5472), corresponding to a relative difference of 18.7%. The seasonal variation was more pronounced in patients >65 years.

The present analyses demonstrate marked variations in the occurrence of sudden death with peaks during morning hours, on Mondays, and during winter months. The findings suggest that the onset of sudden death may be associated with endogenous rhythms and external factors including climatic conditions.