Validation of the Spanish version of the DEMQOL system

Dementia is associated with poor quality of life, but generic measures do not fully capture main aspects of these conditions. Our aim was to validate a Spanish version of the "dementia-specific health-related quality of life" DEMQOL system.

We validated the Spanish DEMQOL and DEMQOL-Proxy in 119 people with dementia from six centers and their caregivers. Patient-reported information, including generic (WHOQOL-BREF) and dementia-specific (DEMQOL) health-related quality of life, depressive symptoms (GDS-15), functional ability (Barthel Index), subjective perception of health and demographic information, was obtained by interview. Proxy-reported information from a family caregiver about the patient's quality of life (DEMQOL-Proxy) was also obtained by interview.

The Spanish DEMQOL showed good psychometric properties. Acceptability (14.3% missing data), internal consistency (Cronbach's alpha = 0.85) and test-retest reliability (ICC = 0.71) were good. A priori hypotheses about the relationship between DEMQOL and the WHOQOL-BREF (psychological and physical domains), GDS-15 and Barthel Index were confirmed, indicating good construct validity. Associations between DEMQOL-Proxy and other measures were weaker. A three-factor solution accounted for 44.4% of the total variance of DEMQOL, and a four-factor solution accounted for 53.3% of the total variance of DEMQOL- Proxy.

The Spanish versions of DEMQOL and DEMQOL-Proxy are reliable and valid in patients with mild/moderate dementia who are living at home.