Measuring the quality of life of family carers of people with dementia: development and validation of C-DEMQOL

We aimed to address gaps identified in the evidence base and instruments available to measure the quality of life (QOL) of family carers of people with dementia, and develop a new brief, reliable, condition-specific instrument. We generated measurable domains and indicators of carer QOL from systematic literature reviews and qualitative interviews with 32 family carers and 9 support staff, and two focus groups with 6 carers and 5 staff. Statements with five tailored response options, presenting variation on the QOL continuum, were piloted (n = 25), pre-tested (n = 122) and field-tested (n = 300) in individual interviews with family carers from North London and Sussex. The best 30 questions formed the C-DEMQOL questionnaire, which was evaluated for usability, face and construct validity, reliability and convergent/discriminant validity using a range of validation measures. C-DEMQOL was received positively by the carers. Factor analysis confirmed that C-DEMQOL sum scores are reliable in measuring overall QOL (ω = 0.97) and its five subdomains: ‘meeting personal needs’ (ω = 0.95); ‘carer wellbeing’ (ω = 0.91); ‘carer-patient relationship’ (ω = 0.82); ‘confidence in the future’ (ω = 0.90) and ‘feeling supported’ (ω = 0.85). The overall QOL and domain scores show the expected pattern of convergent and discriminant relationships with established measures of carer mental health, activities and dementia severity and symptoms. The robust psychometric properties support the use of C-DEMQOL in evaluation of overall and domain-specific carer QOL; replications in independent samples and studies of responsiveness would be of value.