Chua Kia-Chong, Brown Anna, Little Ryan, Matthews David, Morton Liam, Loftus Vanessa, Watchurst Caroline, Tait Rhian, Romeo Renee, Banerjee Sube
Institute of Psychiatry, Psychology and Neuroscience, King's College London, De Crespigny Park, London, SE5 8AF, UK.
School of Psychology, University of Kent, Canterbury, UK.
Qual Life Res. 2016 Dec;25(12):3107-3118. doi: 10.1007/s11136-016-1343-1. Epub 2016 Jun 18.
There is a need to determine whether health-related quality-of-life (HRQL) assessments in dementia capture what is important, to form a coherent basis for guiding research and clinical and policy decisions. This study investigated structural validity of HRQL assessments made using the DEMQOL system, with particular interest in studying domains that might be central to HRQL, and the external validity of these HRQL measurements.
HRQL of people with dementia was evaluated by 868 self-reports (DEMQOL) and 909 proxy reports (DEMQOL-Proxy) at a community memory service. Exploratory and confirmatory factor analyses (EFA and CFA) were conducted using bifactor models to investigate domains that might be central to general HRQL. Reliability of the general and specific factors measured by the bifactor models was examined using omega (ω) and omega hierarchical (ω ) coefficients. Multiple-indicators multiple-causes models were used to explore the external validity of these HRQL measurements in terms of their associations with other clinical assessments.
Bifactor models showed adequate goodness of fit, supporting HRQL in dementia as a general construct that underlies a diverse range of health indicators. At the same time, additional factors were necessary to explain residual covariation of items within specific health domains identified from the literature. Based on these models, DEMQOL and DEMQOL-Proxy overall total scores showed excellent reliability (ω > 0.8). After accounting for common variance due to a general factor, subscale scores were less reliable (ω < 0.7) for informing on individual differences in specific HRQL domains. Depression was more strongly associated with general HRQL based on DEMQOL than on DEMQOL-Proxy (-0.55 vs -0.22). Cognitive impairment had no reliable association with general HRQL based on DEMQOL or DEMQOL-Proxy.
The tenability of a bifactor model of HRQL in dementia suggests that it is possible to retain theoretical focus on the assessment of a general phenomenon, while exploring variation in specific HRQL domains for insights on what may lie at the 'heart' of HRQL for people with dementia. These data suggest that DEMQOL and DEMQOL-Proxy total scores are likely to be accurate measures of individual differences in HRQL, but that subscale scores should not be used. No specific domain was solely responsible for general HRQL at dementia diagnosis. Better HRQL was moderately associated with less depressive symptoms, but this was less apparent based on informant reports. HRQL was not associated with severity of cognitive impairment.
需要确定痴呆症患者健康相关生活质量（HRQL）评估是否抓住了关键要素，从而为指导研究、临床及政策决策形成一个连贯的基础。本研究调查了使用DEMQOL系统进行的HRQL评估的结构效度，尤其关注研究可能对HRQL至关重要的领域以及这些HRQL测量的外部效度。
在社区记忆服务中心，通过868份自评报告（DEMQOL）和909份代理报告（DEMQOL-Proxy）对痴呆症患者的HRQL进行评估。使用双因素模型进行探索性和验证性因素分析（EFA和CFA），以研究可能对一般HRQL至关重要的领域。使用ω系数和ω层次系数检验双因素模型测量的一般因素和特定因素的可靠性。使用多指标多原因模型，根据这些HRQL测量与其他临床评估的关联来探索其外部效度。
双因素模型显示出良好的拟合优度，支持将痴呆症患者的HRQL视为一个普遍概念，它是一系列不同健康指标的基础。同时，还需要其他因素来解释从文献中确定的特定健康领域内项目的残余协方差。基于这些模型，DEMQOL和DEMQOL-Proxy的总体总分显示出极佳的可靠性（ω>0.8）。在考虑了一般因素导致的共同方差后，分量表分数在反映特定HRQL领域的个体差异方面可靠性较低（ω<0.7）。与基于DEMQOL-Proxy的结果相比，基于DEMQOL的结果显示抑郁与一般HRQL的关联更强（-0.55对-0.22）。基于DEMQOL或DEMQOL-Proxy，认知障碍与一般HRQL没有可靠的关联。
痴呆症患者HRQL双因素模型的合理性表明，在探索特定HRQL领域的差异以洞察痴呆症患者HRQL的“核心”内容时，有可能在理论上继续关注对一般现象的评估。这些数据表明，DEMQOL和DEMQOL-Proxy的总分可能是HRQL个体差异的准确测量指标，但不应使用分量表分数。在痴呆症诊断时，没有特定领域能单独决定一般HRQL。较好的HRQL与较少的抑郁症状适度相关，但根据 informant 报告，这种关联不太明显。HRQL与认知障碍的严重程度无关。
