If deaths from accidents are excluded, this term means the unexpected death of an apparently healthy person. CARDIAC ARREST is the most common cause of sudden death. Older people (35 years or above) who suffer cardiac arrest commonly have coronary artery disease (see HEART, DISEASES OF) with restriction or stoppage of blood supply to part of the heart which causes INFARCTION (heart attack). Irregularity of the heartbeat (cardiac ARRHYTHMIA) is another cause. MYOCARDITIS, PNEUMONIA and STROKE can also result in sudden death, as can ASTHMA, anaphylactic shock (see ANAPHYLAXIS), ruptured aortic ANEURYSM, and SUICIDE, the incidence of which is rising, especially among young people, and is over 4,000 a year in the UK.

Sudden death sometimes occurs in infants, usually in the first year of life: this is called SUDDEN UNEXPECTED DEATH IN INFANCY or cot death, the possible causes of which are an ongoing subject for research and debate.

When a person dies unexpectedly the event must be reported to a CORONER, who has the power to decide whether an AUTOPSY is necessary.