Mortality is the risk of dying in a given year, measured by the death rate—the number of deaths occurring per 100,000 people in a population.
What is premature death? Death is inevitable, but a large proportion of individuals die before their time because of illness or injury. As of 2006, the average life expectancy of a newborn was 78 years. One could argue that any death before that age is “premature,” and many people hope to live longer, an expectation that will increase over time. Some studies therefore calculate the years of potential life lost (YPLL) before age 75—which examines the total number of years of life that are lost in a population of 100,000 when deaths occur before age 75.
As a measure of societal distress, this website defines premature mortality as deaths that occur before age 65. Such deaths involve not only adults who succumb to diseases or fatal injuries early in their lives but also infants, children, and adolescents who die from pediatric illnesses or injuries. Such early deaths—which cut off the ability of people to enjoy long, satisfying lives—are more common among disadvantaged populations. (We chose death before age 65 as the threshold for premature death, rather than age 75 or later, because statistics for this age group are readily available and because it is a more conservative measure, preceding average life expectancy by 13 years.)
We calculated premature deaths (before age 65) by deriving the number of deaths in the given year among persons age 0-64 and dividing by the estimated population for all age groups in the same year. This equates to the crude death rate (not age adjusted) for persons age 0-64.
Health is defined not only by the length of life but also its quality. How many years a person lives, and how many years of life lost, carry different meaning depending on the texture and context of one’s life: physical and mental wellbeing and suffering, productivity, hopes and plans, and the family and social environment. We therefore consider morbidity along with mortality. See What is Fair or Poor Health? and What is Chronic Disease?