Measures of Longevity of American Indians

Measures of comparative longevity are often misused by persons describing the differences between the health status of American Indians and that of other Americans. In 1967, the expectation of life at birth for Indians was 64 years and the average age at death was 46 years. For the total population in the United States, the life expectancy was 70 years and the average age at death was 65 years. A common mistake is to compare the Indian average age at death with the life expectancy in the general population; another error is to use the terms as if they meant essentially the same thing. A life expectancy is based on a life-table calculation and represents the average number of years a member of a hypothetical cohort of persons could expect to live at the time of birth. This cohort is assumed to experience throughout its lifetime the set of age-specific death rates observed in the underlying population during a short, fixed observation period. As used by the Indian Health Service, the average age at death simply means the arithmetic mean of the ages of all persons dying during the year in an actual population. The average age at death is of questionable value as a measure of longevity because it ignores the size and age distribution of the population; also, it may not adequately represent the bimodal and skewed age distribution typical of deaths. Nor is a life expectancy meant to forecast; it is based on current death rates rather than on projections of future mortality levels.