Statistical analysis of the standardized mortality ratio and life expectancy.

A new theoretical relation that does not require the constant age-specific mortality ratio assumption is established between the standardized mortality ratio (SMR) and the life expectancy. A set of regression equations is developed from the theoretical relation to derive estimates of the future expectation of life from estimates of the SMR. Curves are presented showing the changes in life expectancy that are associated with a given SMR for individuals aged 25, 45, and 65 years. These results will provide practical applications in estimating remaining life expectancy in epidemiologic studies in which the SMR is the summary statistic. An application is shown for studies in occupational health to develop and illustrate the method.