Although new dementia cases in the United States decreased between 2015 and 2021, the number of people living with the disease continued to increase due to a rapidly aging population, according to the results of a new study.

Specifically, according to the research led by Duke University investigators, dementia incidence in the United States from 3.5% in 2015 to 2.8% in 2021, but the prevalence of dementia continued to increase, with almost 2.9 million beneficiaries of traditional fee-for-service Medicare (12%) living with a dementia diagnosis in 2021 compared with 10.5% in 2015. 

The researchers also noted a greater burden of dementia among marginalized and low-income populations, which they said highlighted the importance of policy approaches to promote equitable dementia care. The study was published Tuesday in the journal The BMJ.

Using medical claims data to determine the incidence and prevalence of dementia by race, sex and neighborhood socioeconomic status, the investigators looked at data for more than 5 million fee-for service Medicare beneficiaries who were aged 66 or more years between 2015 and 2021.

Men (3.5%) had a higher incidence of dementia than did females (3.4%) in 2015, with the difference widening by 2021, when the incidence of disease among men was 2.9% compared with 2.6% among women.

Black participants and those living in lower income neighborhoods had the highest incidence and prevalence of dementia. Black beneficiaries had the highest incidence of dementia (4.2%) in 2015, followed by Hispanic beneficiaries (3.7%) and white beneficiaries (3.4%). Similar statistics were noted in 2021 for Black beneficiaries (3.1%), white beneficiaries (2.8%) and Hispanic beneficiaries (2.6%). 

Better management of cardiovascular risk factors — including hypertension, hyperlipidemia and diabetes — and COVID-19 mortality among beneficiaries were among the potential reasons behind the reduced incidence of dementia, according to the study. The increase in dementia prevalence was attributed to longer life spans, which led to more people developing dementia and living longer after it was diagnosed. 

The study was funded by the Duke University Department of Neurology as well as the Alzheimer’s Association.