Sudden cardiac death refers to: natural death from cardiac causes, heralded by abrupt loss of consciousness within one hour of the onset of acute symptoms.
Sudden infant death refers to: sudden unexpected death of an infant <=2 year of age, with onset of the fatal episode apparently occurring during sleep that remains unexplained after a thorough investigation, including performance of a complete autopsy and review of the circumstances of death and the clinical history.
Background rates of sudden unexpected death will not be limited to age groups but will only be done in databases in which the cause of death can be assessed.