Measuring Quality of Life in Dementia with DEMQOL

This report, published in Health Technology Assessment in March 2005, presents the development and validation of DEMQOL, a new psychometrically rigorous instrument designed to measure health-related quality of life (HRQoL) for individuals with dementia. The study was commissioned by the NHS R&D Health Technology Assessment (HTA) Programme as project number 97/17/16, which directly influences key decision-making bodies like the National Institute for Clinical Excellence (NICE) and aims to improve standards of care within the NHS.

Background and Rationale: Dementia is recognized as one of the most common and serious disorders in later life, causing irreversible decline in intellectual and physical functioning, and having a significant personal, social, health, and economic impact on individuals, their family carers, and health services. While measures of cognitive, functional, and behavioral outcomes are widely used to evaluate dementia interventions, the challenge of measuring broader psychosocial outcomes, such as HRQoL, has only recently begun to be addressed. This challenge is compounded by difficulties in assessing the subjective perceptions and experiences of people with dementia in a reliable and valid way, given impairments in memory, attention, communication, and insight. Existing dementia-specific HRQoL measures had limitations and gaps, particularly in their applicability across varying severity levels and cultural contexts, with only two validated for use in the UK at the time.

Study Objectives: The primary purpose of this study was to develop and validate a psychometrically rigorous measure of HRQoL for people with dementia. Specifically, the new measure was intended to be:

• Suitable for use in the UK.
• Available in self-report (DEMQOL) and proxy-report (DEMQOL-Proxy) versions for people with dementia and their carers, respectively.
• Appropriate for use across mild, moderate, and severe dementia. Crucially, the study aimed to keep the perspective of the person with dementia central throughout all stages of questionnaire development and evaluation.

Methodology: The research employed gold-standard psychometric techniques for the development and evaluation of DEMQOL and DEMQOL-Proxy.

1. Conceptual Framework Development:
   • A comprehensive conceptual framework for HRQoL in dementia was generated through a dual approach:
     • “Top-down”: Involving a review of existing literature and expert consensus from a multidisciplinary research team.
     • “Bottom-up”: Conducting in-depth qualitative interviews with a purposive sample of 19 people with dementia and 20 family carers. Interviews were conducted simultaneously but separately to minimize bias.
   • Initial framework included seven domains (well-being, daily activities satisfaction, cognitive ability satisfaction, social relationships quality, general health perceptions, energy, and aesthetics).
   • The final conceptual framework comprised five domains: daily activities and looking after yourself, health and well-being, cognitive functioning, social relationships, and self-concept.
   • Qualitative findings revealed distinct perspectives: people with dementia focused on the “here and now” and often made positive social comparisons, while carers were more reflective, emphasized changes, and reported limitations and frustrations. These differences highlighted the need for separate self-report and proxy-report instruments.
2. Questionnaire Development and Pre-testing:
   • Items were drafted for each component of the conceptual framework, resulting in preliminary 73-item versions of DEMQOL (self-report) and DEMQOL-Proxy (carer proxy-report).
   • An interviewer-administered format was chosen for both.
   • Preliminary versions underwent pre-testing with 12 people with dementia and 11 carers to clarify wording ambiguities and evaluate time-frame, question stems, and response options.
   • Revisions included adopting a 1-week time-frame and using “How worried have you been about…” as the most easily understood question stem. Response options were refined to an intensity rating (“a lot/quite a bit/a little/not at all”) as participants found these easiest to use, moving away from two-point or feeling-based scales. An interviewer manual was developed to ensure standardized administration and handling of conversational responses.
3. Two-Stage Field Testing:
   • Preliminary Field Test (Item Reduction):
     • Involved 130 people with dementia and 126 carers.
     • Dementia severity was assessed using the Mini Mental State Examination (MMSE) and Clinical Dementia Rating Scale (CDR), and disability with the Barthel Index.
     • Items with poor psychometric performance (based on criteria for missing data, maximum endorsement frequencies (MEF), aggregate adjacent endorsement frequencies (AEF), and redundancy) were eliminated separately for DEMQOL and DEMQOL-Proxy. A modified missing data criterion of ≤30% for DEMQOL and ≤10% for DEMQOL-Proxy was adopted due to the inherent difficulties in this population.
     • Exploratory factor analysis and item convergent/discriminant validity analyses were performed for preliminary scale development.
     • This stage resulted in a shorter, 28-item DEMQOL and a 31-item DEMQOL-Proxy. The DEMQOL showed four preliminary factors (daily activities, memory, negative emotion, positive emotion) and DEMQOL-Proxy showed two (functioning and emotion).
     • Significantly, low correlations between self-reports and proxy reports (0.4 or below for most items) were observed, reinforcing the need for separate measures.
   • Final Field Test (Psychometric Evaluation):
     • Conducted in an independent sample of 101 people with dementia and 99 carers.
     • The item-reduced questionnaires were evaluated for acceptability, reliability, and validity using other validating measures.
     • Validating measures included: dementia-specific HRQoL (QOLAD, DQOL), generic HRQoL (SF-12), depression (GDS-30), disability (Barthel Index), and carer psychological well-being (GHQ-12).
     • Mild/moderate dementia was defined as MMSE ≥ 10, and severe dementia as MMSE < 10. Due to high missing data (68%) in the severe group, DEMQOL validation was only feasible for the mild/moderate group, while DEMQOL-Proxy was validated for both.

Key Findings: Rigorous evaluation with a total of 241 people with dementia and 225 carers demonstrated the following psychometric properties:

• DEMQOL (Self-report):
  • Comparable to the best available dementia-specific HRQoL measures in mild to moderate dementia (MMSE ≥ 10).
  • Not appropriate for use in severe dementia (MMSE < 10) due to high rates of missing data.
  • Showed good acceptability, high internal consistency (Cronbach’s alpha = 0.87), and good test-retest reliability (0.84) in the mild/moderate group.
  • Demonstrated modest evidence of convergent and discriminant validity, correlating moderately with QOLAD and SF-12 MCS, but less so with DQOL and not as expected with depression or disability.
  • Little support for empirically distinct subscales was found in the final factor analysis, which was conceptually less clear than in the preliminary test.
• DEMQOL-Proxy (Carer-report):
  • Comparable to the best available proxy measure in mild to moderate dementia, and shows promise in severe dementia.
  • Demonstrated good acceptability and high internal consistency (Cronbach’s alpha = 0.89) in both mild/moderate and severe dementia subsamples.
  • Test-retest reliability was encouraging (0.75 for mild/moderate, 0.84 for severe), though the severe sample was small and further evaluation is needed.
  • Evidence for convergent and discriminant validity was moderate but mixed; it correlated with QOLAD-Carer and proxy-reported depression but not consistently with SF-12 or disability.
  • Similar to DEMQOL, there was little support for robust subscales in the final factor analysis.

Recommendations for Use: The DEMQOL system has been validated in the UK in a substantial sample of people with dementia and their carers. It provides separate measures for self-report and proxy-report, which allows outcomes assessment across a wide range of dementia severity.

• As DEMQOL and DEMQOL-Proxy provide different but complementary perspectives on quality of life in dementia, the authors recommend using both measures together to maximize data completeness and capture both perspectives.
• In cases of severe dementia (MMSE < 10), only DEMQOL-Proxy should be used, due to the high proportion of missing self-report data in this group.

Future Research Recommendations: The authors recommend further research in three key areas, listed in order of priority:

1. Further Development and Evaluation:
   • Replication of psychometric properties in independent samples, particularly test-retest reliability in larger samples and further investigation of the instrument’s factor structure.
   • Evaluation of responsiveness, which is crucial for assessing the impact of interventions, as no published dementia HRQoL measure has yet evaluated this.
   • Further evaluation of DEMQOL-Proxy in severe dementia with larger samples, and its use with formal and professional carers.
   • Cross-cultural adaptation and validation for use in minority ethnic groups and international studies.
   • Development of population norms to facilitate interpretation of results.
   • Evaluation of the instruments in specific subgroups (e.g., early-onset dementia, primary care, care homes, rare forms) and investigation of its feasibility for economic evaluations by generating utility weights.
2. Methodological Research:
   • Investigation into the relationship between self-report and proxy-report of HRQoL in dementia, including factors that moderate this relationship (e.g., severity, premorbid relationship).
   • Better understanding of the feasibility and validity of self-report of HRQoL in dementia across different severity levels, noting the challenge of defining absolute cut-off points for reliable self-reporting.
   • Exploration of novel approaches to assessing HRQoL, such as objective measures based on behavioral observation, while acknowledging the inherent subjectivity of HRQoL.
3. Evaluative Research:
   • Inclusion of DEMQOL and DEMQOL-Proxy as outcome measures in Randomised Controlled Trials (RCTs) and non-RCT evaluations of interventions and services.
   • Conducting cross-sectional and cohort studies to investigate factors associated with HRQoL in dementia and to identify predictors of changes in HRQoL over time.

The study concludes that quality of life can indeed be measured in dementia, and DEMQOL provides a tool for such assessments, marking important steps towards developing services that enhance and maintain the HRQoL of people with dementia and their carers.

Reference: Smith, S. C., Lamping, D. L., Banerjee, S., Harwood, R., Foley, B., Smith, P., Cook, J. C., Murray, J., Prince, M., Levin, E., Mann, A., & Knapp, M. (2005). Measurement of health-related quality of life for people with dementia: Development of a new instrument (DEMQOL) and an evaluation of current methodology. Health Technology Assessment, 9(10).