Background: Measurements of patient quality of life (QoL) play a major role in the management of dementia. Objective: We investigated the self-proxy discrepancy of QoL ratings in the elderly and the impact of dementia severity on the discrepancy. 

Methods: QoL of 718 patients with dementia and 651 non-demented elderly were rated by themselves and their caregivers (CG) using the Quality of Life-Alzheimer’s Disease (QoL-AD). The impact of the rater on the total and item scores of QoL-AD was analyzed using repeated measures ANOVA and differential response patterns between self and proxy were analyzed using differential item functioning (DIF) analysis. 

Results: Self-rated scores were higher than CG-rated scores in all diagnostic groups. The interaction between rater and diagnostic group was significant in total QoL-AD score and 5 item scores (‘memory’, ‘marriage’, ‘chores around the house’, ‘do things for fun’, and ‘life as a whole’). The strength of the DIF increased with advancing dementia in these items. 

Conclusion: Self-proxy rating discrepancy of QoL was influenced by the presence and severity of dementia only in five items.

Keywords: Caregiver, dementia, discrepancy, proxy, quality of life, self