The Declining Exponential Approximation of Life Expectancy (DEALE) is a simple method for estimating the impact of a disease or intervention on life expectancy. It assumes that the population survival follows a declining exponential curve.


life expectancy in years =

= 1 / (average annual mortality rate)




average annual mortality rate =

= 1 / (life expectancy in years)



• The life expectancy can be determined for a person from actuarial tables, taking account the person's current age, gender and race.


If an intervention or disease changes the average annual mortality rate,


life expectancy with intervention or disease =

= 1 / ((average annual mortality rate) + ((factor) * (change in annual mortality due to intervention or disease)))


increase in life expectancy from an intervention or disease =

= (life expectancy with intervention or disease) – (life expectancy without intervention or disease)



• factor = 1 if it increases mortality and (-1) if it decreases mortality


If actuarial data is not available, life expectancy can be estimated from the following equation, but gender and race effects are ignored (page 887, Beck):


life expectancy in years for a person 20 – 70 years of age =

= (69.5 – (0.80 * (age in years))


life expectancy in years for a person > 70 years of age =

= (51.9 – (0.55 * (age in years))


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