The validation of a caregiver assessment of dementia: the Dementia Severity Scale.

OBJECTIVE

The objective of this study was to refine and validate the Dementia Severity Scale (DSS), a newly developed assessment of dementia severity from a caregiver's perspective. The Dementia Severity Scale is designed to measure deficits in activities of daily living (ADL), behavioral disturbances, and the caregiver's perception of the patient's current cognitive abilities.

METHODS

Community dwelling caregiver/patient dyads were recruited from 12 clinical sites. Patients had a primary dementia diagnosis for at least one year. In this cross-sectional study, caregivers were administered the Dementia Severity Scale, the Quality of Life-Alzheimer's Disease (QOL-AD), the Progressive Deterioration Scale (PDS), and the Neuropsychiatric Inventory (NPI). Patients were administered the Mini-Mental State Examination (MMSE) and the QOL-AD. To evaluate test-retest reliability, 25% of caregivers were randomized to a second visit.

RESULTS

One hundred eighty-three caregiver/patient dyads were recruited. Mean caregiver age was 67.5; mean patient age was 78.8; 93% of patients had probable Alzheimer disease. Eighty-eight (48.1%) patients were male. Exploratory factor analysis established 6 subscales (Activities of Daily Living [ADL], Instrumental ADL [IADL], Communication, Agitation, Memory, and Disorganized Thinking). Cronbach's alphas ranged from 0.82 to 0.90 for the 6 subscales. Test-retest reliability was good with intraclass correlation coefficients ranging from 0.79 to 0.89. DSS subscales were moderately-to-highly correlated with the QOL-AD, NPI, MMSE, and PDS. Subscales significantly discriminated among severity levels of dementia, identified by both physician ratings and MMSE scores.

CONCLUSION

The Dementia Severity Scale demonstrated excellent psychometric properties and appears to be useful both in clinical practice and research endeavors. Further research is needed to establish the longitudinal sensitivity of the Dementia Severity Scale to the progression of dementia.