BACKGROUND: Knowledge of causes of sudden cardiac death (SCD) according to age is important in clinical decision-making and to lower the risk of SCD in family members of SCD victims.

OBJECTIVE: To report overall and sex-stratified causes of SCD according to age in persons aged 1-49 years.

METHODS: The study population consisted of all persons in Denmark aged 1-35 years in 2000-09 and 36-49 years in 2007-09, which equals 27.1 million person-years. Danish death certificates, discharge summaries, autopsy reports, and data from nationwide registries were used to identify all SCD cases. The SCD cases were divided into 5-year age groups.

RESULTS: In the 10-year study period, there were 14,294 deaths, of which 1,362 (10%) were classified as SCD. Potentially inherited cardiac disease accounted for a large proportion (43-78%) of autopsied SCD in all age groups. A significant proportion (19-54%) of SCD was caused by sudden arrhythmic death syndrome in all age groups. Autopsy rates among both sudden unexpected death cases and SCD cases declined significantly with increasing age (74% in the youngest age group vs. 35% in the oldest).

CONCLUSION: The proportion of SCD cases that were identified with a potentially inherited cardiac disease postmortem was high in all studied age groups, while autopsy rates among cases of sudden and unexpected death declined markedly with increasing age. Our findings indicate that diagnoses of inherited heart disease are likely missed in some SCD cases, along with the opportunity for treatment and prevention among surviving relatives.