The GAME estimate of reduced life expectancy

The Declining Exponential Approximation of Life Expectancy (DEALE) is a simple method of estimating the impact of excess mortality on life expectancy, but it can lead to considerable bias due to the implicit constant baseline and excess mortality rates. This article presents a new method that does not use constant mortality rates. The variability of the baseline mortality is modeled using gamma (GA) distributions. Excess mortality rates are modeled using mixed-exponential (ME) distributions, which is appropriate if the excess mortality rate is nonincreasing, convex, and smooth. The new gamma mixed-exponential (GAME) estimate is convenient enough to replace the DEALE in formal decision analyses. The error from assuming gamma distributions for the Dutch baseline mortality was shown to be less than 2 months and typically about 1 month. Therefore, the GAME estimate is accurate enough to replace more elaborate methods, provided the mixed-exponential model is an appropriate model for the excess mortality.