Medicare Claims Data Underestimate Hallucinations in Older Adults With Dementia

Administrative claims data are used to study the incidence and outcomes of dementia-related hallucinations, but the validity of International Classification of Diseases (ICD) codes for identifying dementia-related hallucinations is unknown.

We analyzed Medicare-linked survey data from 2 nationally representative studies of U.S. older adults (the National Health and Aging Trends Study and the Health and Retirement Study) which contain validated cognitive assessments and a screening question for hallucinations. We identified older adults who had dementia or were permanent nursing home residents, and we combined this with questionnaire responses to define dementia-related hallucinations. Using Medicare claims data, we calculated the sensitivity, specificity, positive predictive value (PPV), and negative predictive value (NPV) of ICD codes for dementia-related hallucinations overall and within prespecified strata of age, neurologic comorbidity, and health care utilization.

We included 2,337 older adults with dementia in our cohort. Among 3,789 person-years of data, 1,249 (33.0%) had hallucations, and of these 286 had a qualifying ICD code for dementia-related hallucinations or psychosis (sensitivity 22.9%). Of 2,540 person-years of dementia without hallucinations, 284 had a diagnosis code for hallucinations (specificity 88.8%). PPV was 50.2%, and NPV was 70.1%. Sensitivity was greatest (57.0%) among those seeing a psychiatrist. Otherwise, there were no significant differences in sensitivity, specificity, PPV, or NPV by age, neurologic diagnosis, or neurologist care.

Dementia-related hallucinations are poorly captured in administrative claims data, and estimates of their prevalence and outcomes using these data are likely to be biased.