Schizophrenia ups likelihood of dementia

Compared with older adults without serious medical illness (SMI), the prevalence and incidence of dementia diagnoses are markedly increased among those with schizophrenia across a wide age range, possibly because of cognitive and functional deterioration related to schizophrenia or factors contributing to other types of dementia, results of a recent study have shown.

“The implications of high rates of dementia among adults with schizophrenia are substantial for families and for the service system, with high levels of service required for individuals with a combination of disabling conditions who may differ in treatment pathways,” pointed out the authors. [JAMA Psychiatry 2021;doi:10.1001/jamapsychiatry.2021.0042]

At 66 years of age, the prevalence of dementia (defined using the Centers for Medicare & Medicaid Services Chronic Conditions Warehouse diagnosis codes for Alzheimer’s disease and related disorders or senile dementia) diagnoses was 21.5 times higher in the group with schizophrenia vs the group without SMI (27.9 percent vs 1.3 percent). The difference in prevalence of dementia diagnoses between the group with schizophrenia and the group without SMI was reduced (70.2 percent and 11.3 percent) by 80 years of age.

Among individuals with schizophrenia but no pre-existing dementia, the annual incidence of dementia diagnoses increased from 52.5 per 1,000 person-years for adults 66 years of age to 216.2 per 1,000 person-years for adults 80 years of age.

Among individuals without SMI who had no pre-existing dementia, the corresponding increase was from 4.5 per 1,000 person-years for adults 66 years of age to 32.3 per 1,000 person-years for adults 80 years of age.

In the retrospective cohort study, researchers extracted data of 8,011,773 adults (female, 63.4 percent; mean age, 74.0 years) ≥66 years of age from national Medicare Parts A, B and D claims from 1 January 2007 to 31 December 2017, with a random sample of approximately 50 percent of all Part-D enrolled beneficiaries with free-for-service coverage included.

The cohort with schizophrenia included 74,170 adults (female, 56.6 percent; non-Hispanic White, 68.6 percent) aged ≥66 years with ≥12 months of continuous enrollment in the free-for-service Medicare and Part D and ≥2 outpatient claims or ≥1 inpatient claim for schizophrenia during the qualifying period. The comparison group included 7,937,603 adults (female, 63.5 percent; non-Hispanic White, 81.4 percent) aged ≥66 years with ≥12 months of continuous enrollment in the free-for-service Medicare and Part D and without a diagnosis of schizophrenia, bipolar disorder, or recurrent major depressive disorder.