Background: Quality of life (QoL) is increasingly used to characterize the impact of disease and the efficacy of interventions.
Methods: Prospective cohort study in patients' and proxies' homes with 137 patients with dementia (age 52 to 88; Mini-Mental Status Examination (MMSE) 3 to 28) and their proxies (age 43 to 90). MMSE, Behave-AD, Geriatric Depression Scale (GDS), and Bayer-ADL scale (B-ADL), and the Euroqol (EQ-5D; patient self-rating, proxy self-rating, and proxy-rating of patient).
Results: B-ADL impairment and Behave-AD total score increased with dementia severity (Kruskal-Wallis p < 0.001 and p = 0.023, respectively). Patients' self-rated QoL and proxies' self-rated QoL were unrelated to dementia severity (p = 0.148 and p = 0.414, respectively). The difference between patients' self- and proxies'-rating of the patient's QoL correlated with the patient's MMSE (Spearman's rho = -0.434; p < 0.001), even if analysis was constrained to patients with mild AD (rho = -0.328; p = 0.019). The proxies' rating of the patients QoL was not only correlated with cognitive and behavioral symptoms of the patient but also with mood (GDS-score; rho = 0.317; p < 0.001) and cognitive abilities (verbal fluency; rho = 0.209; p < 0.018) of the proxy.
Conclusion: Proxies' assessment of the patients' QoL is related to the proxies' health, and the difference of patient's and proxie's QoL-rating is correlated with dementia severity even in mild dementia stages. QOL measures use ratings of the individual to assess the impact of symptoms and disorders on everyday life. In dementia patients, however, this impact is not captured since patients' and proxies' self-assessment of their own QoL do not reflect severity of disease whatsoever. Patients' and proxies' influencing variables render the score obtained with generic quality of life assessment meaningless in capturing the impact of dementia. Decisions on initiation or discontinuation of treatment or allocation of other resources for patients with dementia therefore need not depend on generic assessment of quality of life.