Mitnitski A B, Mogilner A J, Rockwood K
Department of Mechanical Engineering, Ecole Polytechnique, Montreal, Quebec H3C 3A7.
ScientificWorldJournal. 2001 Aug 8;1:323-36. doi: 10.1100/tsw.2001.58.
This paper develops a method for appraising health status in elderly people. A frailty index was defined as the proportion of accumulated deficits (symptoms, signs, functional impairments, and laboratory abnormalities). It serves as an individual state variable, reflecting severity of illness and proximity to death. In a representative database of elderly Canadians we found that deficits accumulated at 3% per year, and show a gamma distribution, typical for systems with redundant components that can be used in case of failure of a given subsystem. Of note, the slope of the index is insensitive to the individual nature of the deficits, and serves as an important prognostic factor for life expectancy. The formula for estimating an individual's life span given the frailty index value is presented. For different patterns of cognitive impairments the average within-group index value increases with the severity of the cognitive impairment, and the relative variability of the index is significantly reduced. Finally, the statistical distribution of the frailty index sharply differs between well groups (gamma distribution) and morbid groups (normal distribution). This pattern reflects an increase in uncompensated deficits in impaired organisms, which would lead to illness of various etiologies, and ultimately to increased mortality. The accumulation of deficits is as an example of a macroscopic variable, i.e., one that reflects general properties of aging at the level of the whole organism rather than any given functional deficiency. In consequence, we propose that it may be used as a proxy measure of aging.
本文提出了一种评估老年人健康状况的方法。虚弱指数被定义为累积缺陷（症状、体征、功能障碍和实验室异常）的比例。它作为一个个体状态变量，反映疾病的严重程度和接近死亡的程度。在一个具有代表性的加拿大老年人数据库中，我们发现缺陷以每年3%的速度累积，并呈现伽马分布，这对于具有冗余组件的系统来说是典型的，在给定子系统出现故障时可以使用这些冗余组件。值得注意的是，该指数的斜率对缺陷的个体性质不敏感，并且是预期寿命的一个重要预后因素。给出了根据虚弱指数值估计个体寿命的公式。对于不同模式的认知障碍，组内平均指数值随认知障碍的严重程度增加而增加，并且指数的相对变异性显著降低。最后，虚弱指数的统计分布在健康组（伽马分布）和患病组（正态分布）之间有明显差异。这种模式反映了受损生物体中未得到补偿的缺陷增加，这将导致各种病因的疾病，并最终导致死亡率上升。缺陷的累积是一个宏观变量的例子，即一个反映整个生物体水平上衰老的一般属性而不是任何特定功能缺陷的变量。因此，我们建议它可以用作衰老的替代指标。
