Models of health-related quality of life in a population of community-dwelling Dutch elderly

Objective: Though health-related quality of life (HRQoL) is now commonly me asured as an outcome in clinical trials, the relationships between its comp onents remain unclear. The relation of physical symptoms, physical function , and psychological symptoms to each other and to overall quality of life i s of special interest. Method: Cross-sectional data from 5279 community-dwe lling elders who participated in the Groningen Longitudinal Aging Study wer e analyzed using structural equation modeling techniques. Three models were examined. One "Linear" model included: number of chronic medical condition s, physical symptoms, physical functioning, activity interference, social f unction, perceived health and overall quality of life in a simple linear pr ogression. Another `non-linear' model included these variables, but allowed effects between non-adjacent variables. A third `non-linear' model include d these variables plus anxiety and depressive symptoms. Results: The Linear Model did not satisfactorily account for the observed data [X-2(15(df)) = 2946.96], so the saturated Non-Linear Model, incorporating paths between no n-adjacent components, is described. When anxiety and depressive symptoms w ere added to this Non-Linear Model, they fit best in a position mediating t he relation between perceived health and overall quality of life [X-2(5(df) ) = 136.78]. Conclusions: Overall quality of life appears to be related to symptom status as directly as it is related to functional status. Anxiety a nd depressive symptoms appear to mediate the relation between general healt h perceptions and overall quality of life. Quality of life measures should therefore include assessments of physical and psychological symptom severit y as well as functional status if they are to truly reflect what matters to patients. The disability-adjusted life year (DALY) measure used by the WHO may inadequately reflect the effect of symptoms on patient's quality of li fe.