影響平均餘命增長之生命表特性及其相關死亡率模式分析

Effect of life table indices and a related mortality model on increase of life expectancy

目標：探討死亡年齡變異、存活曲線矩形化間之生命表特性及相關的死亡率模式對平均餘命的影響。方法：利用1998-2016年台灣生命表資料，以各類相關指標測量存活曲線矩形化與死亡年齡變異趨勢。並以相關死亡率模式中重要的混合模式，探討平均餘命增長變化受到死亡率下降與遲緩衰老步調下降消長影響情況。結果：存活曲線間逐漸呈現矩形化的情況，且死亡年齡變異也呈下降狀態；以年齡95歲為上限利用面積差異百分比來檢測矩形化，結果顯示矩形化逐漸趨向平均餘命極限。另透過死亡率混合模式的分析結果得知平均餘命增長趨勢，其中32%是受到死亡率下降的影響，而受到延遲老化的影響則為68%。結論：各種指標均顯示存活曲線有逐漸矩形化的情況，死亡年齡的變異則是呈現下降的趨勢，平均餘命的增長受到一定的限制。從死亡率混合模式分析結果顯示這些年來平均餘命受到遲緩衰老的影響遠較死亡率下降來的大，對於平均餘命的展延，遲緩衰老當扮演舉足重的角色。（台灣衛誌 2020；39(1)：74-89）

Objectives: To investigate the effect of variation in age at death and rectangularity in the survival curve on the increase of life expectancy and further investigate this phenomenon by using a hybrid mortality model. Methods: By using life table data in Taiwan, we measured the rectangular trend in survival curves and variation of age at death on the basis of related life table indices. We then applied a hybrid mortality model to interpret the effects of declining mortality and senescence-slowing on life expectancy. Results: The survival curve, which is closely related to life expectancy, gradually became rectangular from 1998 to 2016, and the variation of age at death declined. We measured the rectangularity of survival curve by setting the upper limit age of 95 years through using the percentage difference in area and found that rectangularity gradually approached the limit. Analysis using the hybrid mortality model revealed that 32% and 68% of the increase of life expectancy resulted from declining mortality and senescence-slowing, respectively. Conclusions: All indicators pointed to the survival curve gradually becoming rectangular and the variation of age at death trending downward, implying that human life expectancy is approaching a certain limit. The hybrid model of mortality revealed that the increase of life expectancy was affected more by senescence-slowing than by declining mortality. (Taiwan J Public Health. 2020;39(1):74-89)