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

Purpose: 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.
Methods: 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.
Results: 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.
Conclusions: 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.