The authors report that 11.6 million years of life were lost to death in Germany in 2017 (1). This is somewhat surprising. One would spontaneously assume that an infinite number of years of life are lost due to the sum of all deaths. The methodological background is that the authors correlate every death with the number of years of life that a person of a corresponding age can still expect under favorable conditions. The favorable-condition residual life expectancies are determined as a best-of from age-specific mortality rates in the individual federal states of Germany. Since there is no mortality without death, this is to a degree a case of the dog chasing its tail.
What applies to death from any cause also applies, to a lesser extent, to years of life lost (YLL) as a result of certain causes of death: contrary to what one might assume, the reported 1710791 YLL due to ischemic heart disease do not represent the life-years that would be gained if coronary heart disease (CHD) would be eliminated as a cause of death. In a logically consistent manner, residual life expectancies would have to be used from a life table that has been adjusted for CHD as a possible cause of death. The corresponding life tables are known as “cause-elimination life tables” (2).
If one gradually eliminates all causes of death, the residual life expectancy becomes infinitely large according to intuition. As compared to the method adapted by Wengler et al. (1) in the Global Burden of Disease Study, the procedure is more robust, since the dependency of the residual life expectancy on the (more or less arbitrary) choice of the subregions considered for the best-of determination (districts, spatial planning regions, federal states?) is no longer applicable.
Regardless of the preferred method, one aspect should not be left unmentioned: quantitative statements on the potential for prevention implicitly use a problematic assumption, namely independence for causes of death. In fact, a potentially life-shortening disease rarely comes alone.
References
- 1.Wengler A, Rommel A, Plaß D, et al. Years of life lost to death—a comprehensive analysis of mortality in Germany conducted as part of the BURDEN 2020 project. Dtsch Arztebl Int. 2021;118:137–144. doi: 10.3238/arztebl.m2021.0148. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 2.Arias E, Heron M, Tejada-Vera B. United States life tables eliminating certain causes of death, 1999-2001. Natl Vital Stat Rep. 2013;61:1–128. [PubMed] [Google Scholar]