Older adults with schizophrenia may have increased risk for dementia

Older adults with schizophrenia had an increased risk for a dementia diagnosis, according to results of a retrospective cohort study published in JAMA Psychiatry. 

Compared with adults aged 66 years or older without serious mental illness, those with schizophrenia showed a higher likelihood of developing dementia, with risk increasing with age. The researchers noted that the link between schizophrenia and dementia is not well understood, which prompted them to perform this study.

“The early dementia diagnoses are not primarily Alzheimer’s disease or vascular dementia,” T. Scott Stroup, MD, MPH, of the department of psychiatry at Columbia University Vagelos College of Physicians and Surgeons, told Healio Psychiatry. “Instead, because cognitive problems are a core component of schizophrenia, factors related to schizophrenia itself and the cumulative effect of other risk factors for dementia may mean that individuals in this group cross a cognitive functioning threshold for a clinical dementia diagnosis sooner.”

This current study involved a 50% random national sample of over 8 million adults aged 66 years or older on Medicare with fee-for-service plans and Part D prescription drug coverage from January 2007 to December 2017. Included adults with schizophrenia had at least 12 months of continuous enrollment in fee-for-service Medicare and Part D and at least two outpatient claims or one inpatient claim for schizophrenia during the qualifying years. The other group of adults had at least 12 months of continuous enrollment in fee-for-service Medicare and Part D, without a diagnosis of schizophrenia, bipolar disorder or recurrent major depressive disorder.

Results showed the prevalence of dementia diagnosis among adults aged 66 years was 27.9% for those with schizophrenia compared with 1.3% for those without serious mental illness. By age 80 years, the prevalence increased in both groups, for 70.2% in those with schizophrenia and 11.3% in those without serious mental illness.

Black individuals had a prevalence of dementia of 28.8% at age 66 years and 74.6% at age 80 years compared with 27.6% and 69.3% at ages 66 years and 80 years, respectively, among non-Hispanic white individuals. Hispanic individuals had a prevalence of 28.6% and 67.7% at ages 66 and 80 years, respectively.

“Going forward, we hope to identify the risk factors for early dementia diagnoses in this population so that we can develop prevention strategies,” Stroup said. “We will also try to determine the best treatment strategies for people who are diagnosed with both schizophrenia and dementia.”