Seasonal Variation in Sudden Cardiac Death: Insights from a Large United Kingdom Registry

Background: Sudden cardiac death (SCD) is relatively common and may occur in apparently healthy individuals. The role of seasonal variation as a risk factor for SCD is poorly understood. The aim of this study was to investigate whether SCD exhibits a predilection for specific seasons.

Methods: We reviewed a database of 4751 cases of SCD (mean age 38 ± 17 years) referred to our Center for Cardiac Pathology at St George's University of London between 2000 and 2018. Clinical information was obtained from referring coroners who were asked to complete a detailed questionnaire. All cases underwent macroscopic and histological evaluation of the heart, by expert cardiac pathologists.

Results: SCD was more common during winter (26%) and rarer during summer (24%), p = 0.161. Significant seasonal variation was not observed among cases of sudden arrhythmic death syndrome (SADS, 2910 cases) in which the heart is structurally normal. In contrast, a significant difference in seasonal distribution among decedents exhibiting cardiac structural abnormalities at the post-mortem examination (n = 1841) was observed. In this subgroup, SCDs occurred more frequently during winter (27 %) compared to summer (22%) (p = 0.007). In cases diagnosed with a myocardial disease (n = 1399), SCD was most common during the winter (27%) and least common during the summer (22%) (p = 0.027).

Conclusions: While SADS occurs throughout the year with no seasonal variation, SCD due to structural heart disease appears to be more common during the winter. Bio-meteorological factors may be potential triggers of SCD in individuals with an underlying structural cardiac abnormality.