Supplementary Material for: Predictive Validity of Two Physical Frailty Phenotype Specifications Developed for Investigation of Frailty Pathways in Older People

Background: For investigating the relationship of frailty with physical, psychological, and social conditions on pathways, the frailty definition should ideally exclude these conditions. Based on the frailty phenotype, 2 candidate physical frailty specifications or instruments with 3 indicators, namely slowness, weakness, and exhaustion, and 4 indicators with addition of weight loss were previously developed, and had their construct and concurrent validity demonstrated. Objective: This study seeks to evaluate the predictive validity of 2 candidate physical frailty specifications with respect to death, functional impairment, and poor quality of life in older people. Methods: For 4,368 respondents aged 65-89 years from wave 2 of the English Longitudinal Study of Ageing, confirmatory factor analysis is performed for these 2 physical frailty specifications to obtain unique factor scores for each respondent. Prediction of death, basic and instrumental activities of daily living (BADL and IADL) difficulty, and poor quality of life (reverse of Control, Autonomy, Self-realization, and Pleasure [19 items] or CASP-19) 2 years later by factor scores for these 2 specifications is evaluated using standardized coefficients, c-statistics, and r2 values from regression analyses. Their performance is compared with those of alternative specifications with 3 (slowness, weakness, and weight loss) and 5 indicators (slowness, weakness, exhaustion, weight loss, and low physical activity), and Frailty Index (FI). Results: For the 2 candidate specifications, an increase of 1 standard deviation (SD) predicts 50-57% increase in odds of death, 0.10-15 SD increase in change in BADL or IADL difficulty, and poor quality of life at 2 years. They predict these outcomes as well or better than the alternative specification with 3 indicators, but marginally worse than that with 5 indicators. Compared with FI, they predict death and poor quality of life similarly, but perform worse for functional impairment. Minor differences are observed across gender. Conclusion: Reasonable predictive validity of 2 candidate physical frailty specifications based on the frailty phenotype with 3 and 4 indicators is demonstrated for death, functional impairment, and poor quality of life. These findings offer evidence to support their suitability for employment in investigating frailty pathways in older people.

研究背景：为探究衰弱与躯体、心理及社会状态在衰弱发病通路中的关联，理想的衰弱定义应排除上述因素。基于衰弱表型（frailty phenotype），既往已开发出2种候选躯体衰弱评估维度或工具：其一包含3项指标，即步速缓慢、肌力减退与疲乏感；其二在此基础上增加体重下降，共4项指标，且二者的结构效度与同时效度均已得到验证。研究目的：本研究旨在评估上述2种候选躯体衰弱评估维度对老年人死亡、功能障碍及生活质量低下的预测效度。研究方法：本研究纳入英国老龄化纵向研究（English Longitudinal Study of Ageing, ELSA）第二波调研中4368名年龄介于65~89岁的受访者。针对上述2种躯体衰弱评估维度开展验证性因子分析，为每名受访者生成唯一的因子得分。采用回归分析得到的标准化系数、C统计量（c-statistics）与决定系数（r²），评估上述2种维度的因子得分对2年后的死亡结局、基础日常生活活动能力（basic activities of daily living, BADL）与工具性日常生活活动能力（instrumental activities of daily living, IADL）障碍，以及生活质量低下（即控制、自主、自我实现与愉悦感量表19条目版，CASP-19的反向得分）的预测效果。同时将其预测性能与另外2种评估维度进行对比：一种为包含3项指标（步速缓慢、肌力减退与体重下降）的维度，另一种为包含5项指标（步速缓慢、肌力减退、疲乏感、体重下降与低体力活动）的维度，以及衰弱指数（Frailty Index, FI）。研究结果：对于上述2种候选评估维度，因子得分每增加1个标准差（SD），可预测2年后的死亡风险升高50%~57%，BADL或IADL障碍程度增加0.10~0.15个标准差，同时生活质量低下的风险升高。二者对上述结局的预测效果优于或等同于3项指标的评估维度，但略逊于包含5项指标的评估维度。与衰弱指数（FI）相比，二者对死亡与生活质量低下的预测效果相当，但在功能障碍的预测上表现更差。不同性别间仅存在微小差异。研究结论：本研究证实，基于衰弱表型开发的、分别包含3项与4项指标的2种候选躯体衰弱评估维度，对老年人的死亡、功能障碍及生活质量低下均具有良好的预测效度。本研究结果为这类维度用于老年人衰弱发病通路相关研究提供了证据支持。