Reliability, validity and clinical correlates of the Quality of Life in Alzheimer's disease (QoL-AD) scale in medical inpatients

Abstract

Background: There is a lack of standardisation in quality of life (QoL) measurements to be used in older multimorbid patients. An ideal QoL measurement should be reliable, valid, subjective, multidimensional, feasible and generic. We hypothesised that the QoL-AD (Quality of Life in Alzheimer's Disease) scale could have these properties. Our aim was to determine the psychometric properties and clinical correlations of QoL-AD in a population of elderly, multimorbid medical inpatients. Methods: QoL-AD was performed in 200 medical inpatients, and available caregivers. Reliability was determined using cronbach's alpha and corrected item-total correlations. The agreement between patient and proxy ratings were examined using intra-class correlations (ICC). Correlations between QoL-AD and demographic data, comorbidity, cognitive tests, ADL (activities of daily living) and depression were examined. To characterise the underlying constructs of QoL-AD, an exploratory factor analysis was performed. Results: In total, 199 patients fulfilled the QoL-AD rating, with 139 proxy ratings. Cronbach's alpha (95% CI) was 0.74 (0.68-0.79) for patients and 0.86 (0.83-0.90) for proxies. Patient-proxy ICC (95% CI) was 0.31 (0.16-0.46). Lower QoL was correlated to depression, cognitive impairment, ADL impairment and solitary living, but not with comorbidity. The factor analysis gave a three-factor solution, with factors representing phsyical, social and psychological well-being. Conclusion: The QoL-AD scale showed some promising properties but more research is needed before it can be recommended in this setting. If replicated, the finding that cognitive impairment, depression and ADL impairment were more associated with lower QoL than somatic comorbidity could have clinical implications for further studies aiming to improve QoL in this population.