Mortality

Mortality refers to the occurrence of death within a defined population. In epidemiology and medical research, mortality is typically expressed as a rate (the number of deaths per 1,000 or 100,000 people in a given population over a defined time period, usually one year) or as a proportion (the percentage of people in a group who die from a particular condition). Mortality data are fundamental to understanding the burden of disease, evaluating interventions, and tracking public health trends.

In cardiology, several mortality measures are important. All-cause mortality is the death rate from any cause and is the most clinically relevant overall outcome in clinical trials. Cardiovascular mortality refers specifically to deaths attributed to heart disease or stroke. Sudden cardiac death is a specific form of cardiovascular mortality in which death occurs rapidly (within an hour of symptom onset) from a cardiac cause, most commonly an arrhythmia.

In cardiac arrest, high early mortality is well-recognised: around 80 to 90% of out-of-hospital cardiac arrests are fatal. Among survivors, however, significant morbidity including cognitive impairment, psychological difficulties, and physical deconditioning is also common. This distinction between mortality (death) and morbidity (illness and disability in survivors) is important in understanding the full impact of cardiac arrest as a public health problem.

In clinical trials of cardiac interventions, mortality is typically a primary endpoint. Treatments such as ACE inhibitors, beta-blockers, and ICD implantation have all been shown to reduce all-cause mortality in randomised trials in heart failure patients, forming the evidence base for current guidelines. For families of cardiac arrest survivors, population mortality statistics can be distressing to encounter; it is worth remembering that statistics describe populations and cannot determine outcomes for any individual.