Abstract Body (Do not enter title and authors here): Introduction: Data on the occurrence of unexpected sudden cardiac death (SCD) in different seasons are scanty and needs further exploration.
Methods: Consecutive series of all unexpected SCD victims (n=5,869) who underwent medico-legal autopsy obligated by the Finnish law were prospectively collected from the geographically defined area in the Northern Finland during a twenty years period from 1998 to 2017. The seasonal variation of SCD and its possible causes were assessed in this large SCD victim cohort.
Results: Unexpected SCD occurred more frequently during the first quarter of a year (from January to March) than during the other quarters (Figure 1). The occurrence of SCD during the twenty years follow-up was 4.5±0.24 during the first quarter of the year per month and 3.9±0.12 during the other quarters of the year per month on average (SCDs during the quarter of a year per month on average per 100,000 inhabitants per year, p<0.001) (Figure 2). The weather was colder during the first quarter of the year (average temperature -9.1 degrees centigrade) than during the other quarters (average temperature +5.7 degrees centigrade). The snow cover was the largest during the first quarter of the year.
Conclusion: Unexpected SCD occurred more commonly during the first quarter of a year (from January to March) than during the other quarters (from April to December). Cold weather, and perhaps winter-time physical activities in cold environment such as removal of snow, may have contributed to the increased occurrence of SCD during the first quarter of the year.