Horiuchi S, Wilmoth J R
Laboratory of Populations, Rockefeller University, New York, NY 10021-6399, USA.
Demography. 1998 Nov;35(4):391-412.
The rate of mortality increase with age tends to slow down at very old ages. One explanation proposed for this deceleration is the selective survival of healthier individuals to older ages. Data on mortality in Sweden and Japan are generally compatible with three predictions of this hypothesis: (1) decelerations for most major causes of death; (2) decelerations starting at younger ages for more "selective" causes; and (3) a shift of the deceleration to older ages with declining levels of mortality. A parametric model employed to illustrate the third prediction relies on the distinction between senescent and background mortality. This dichotomy, though simplistic, helps to explain the observed timing of the deceleration.
随着年龄增长，死亡率上升的速率在极高龄时往往会放缓。针对这种减速现象提出的一种解释是，更健康的个体具有选择生存至更高龄的能力。瑞典和日本的死亡率数据总体上与该假说的三个预测相符：（1）大多数主要死因的死亡率减速；（2）对于更具“选择性”的死因，减速始于较年轻的年龄；（3）随着死亡率水平下降，减速点向更高龄推移。用于说明第三个预测的参数模型依赖于衰老死亡率和背景死亡率之间的区别。这种二分法虽然过于简单，但有助于解释观察到的减速时间。
