Behavioral versus Biological Definitions of Dementia Symptoms: Recognizing that Worthwhile Interventions already Exist.

Background: The 2018 Alzheimer's Disease Facts and Figures special report includes two new guidelines for measuring dementia symptoms. The first requires that a biomarker (biological factor) be added to a doctor's clinical judgment of the cause of symptoms when determining whether dementia is present. The second involves identifying four stages of dementia: normal cognition, preclinical, MCI and dementia. Now only those with defining brain pathologies and significant symptoms will be judged to be persons with stage 4 dementia. This article examines the implications of adopting these two new guidelines. The implications are in terms of whether worthwhile dementia interventions can be said to exist, and the extent to which symptoms have to change for an intervention to be judged to have reduced the prevalence of dementia.

Methods: A cost-benefit framework is used to examine the implications of the new guidelines. To undertake a cost-benefit analysis (CBA) a measure of dementia symptoms change is required for any intervention to be judged effective. A behavioral measure of dementia symptoms is thought more useful than a biological one. The instrument that is recommended and explained is the clinical dementia rating (CDR) scale, which is measured on a 0-to-18 interval. Using this instrument, three CBAs can be shown to exist, and from a contracted version of the CDR, estimates of the prevalence rates for the four stages of dementia are derived. The implications for future dementia research of using the full CDR instrument is presented in the discussion section.

Results: The three CBAs that are reported and explained are years of education, Medicare eligibility and hearing aids. For each intervention, the analysis is in terms of demonstrating that it is effective, beneficial and socially worthwhile.

Conclusions: By using a behavioral rather than a biological definition of dementia symptoms, we can show that worthwhile interventions already exist.