Hirsch H R
Department of Physiology, College of Medicine, University of Kentucky, Lexington 40536-0084.
Exp Gerontol. 1994 Mar-Apr;29(2):119-37. doi: 10.1016/0531-5565(94)90046-9.
Longitudinal Gompertzian analysis yields the counterintuitive conclusion that an improved environment can cause a decrease in maximum lifespan. The basis for this conclusion is examined. Results include the following: 1) The use of a specified high mortality rate as a criterion for maximum lifespan is arbitrary and leads to a calculated lifespan which is quite sensitive to the value of the criterion. 2) The definition of lifespan as the age to which a specified small population fraction survives is less arbitrary and less sensitive to the chosen criterion value. 3) However, the use of a survival criterion for lifespan in place of a mortality-rate criterion does not eliminate the seeming contradiction between environmental improvement and decreased lifespan. 4) Mortality rates can be approximated in semilogarithmic coordinates by three straight-line segments. The first segment, applicable through age 85, is the conventional Gompertz function. The second segment, representing ages 85 through 96, has a lower slope than the first, while the third segment, representing ages 96 through 124, has a negative slope. 5) The mortality rate obtained by extrapolating the first segment to a nominal age of maximum lifespan differs markedly from the true mortality rate at that age. 6) The conclusion that an improved environment is associated with a reduction in lifespan arises as a consequence of such an extrapolation.
纵向的冈珀茨分析得出了一个与直觉相悖的结论，即环境改善可能会导致最大寿命缩短。本文对此结论的依据进行了研究。结果如下：1）将特定的高死亡率用作最大寿命的标准是随意的，并且会得出对该标准值非常敏感的计算寿命。2）将寿命定义为特定小比例人口存活到的年龄，这种定义的随意性较小，对所选标准值的敏感性也较低。3）然而，使用生存标准来定义寿命而非死亡率标准，并不能消除环境改善与寿命缩短之间表面上的矛盾。4）死亡率在半对数坐标中可以用三段直线近似。第一段适用于85岁之前，是传统的冈珀茨函数。第二段代表85岁至96岁，其斜率低于第一段，而第三段代表96岁至124岁，斜率为负。5）将第一段外推到名义最大寿命年龄所得到的死亡率与该年龄的真实死亡率明显不同。6）环境改善与寿命缩短相关这一结论是这种外推的结果。
