Dementia Incidence and Prevalence: What’s Changing in Medicare Data?

Among Medicare beneficiaries in the US, the incidence of dementia decreased from 2015 to 2021, while the prevalence increased, according to the results of a study published in the British Medical Journal.

Dementia burden in the United States is expected to become a leading driver of morbidity and double to nearly 14 million people by 2060. Dementia is known to disproportionately affect marginalized populations. However, limited research exists on recent dementia incidence and prevalence trends.

Researchers from Duke University School of Medicine sourced data from the Centers for Medicare and Medicaid Services (CMS) Virtual Research Data Center (VRDC) to investigate incidence and prevalence of dementia among US Medicare beneficiaries in key subgroups. Adults aged 66 years and older with at least 1 year of continuous fee-for-service enrollment and no claims for dementia (N= 5,025,039) were evaluated for the onset of dementia between 2015 and 2021. Trends were assessed among age, gender, race and ethnicity, and neighborhood socioeconomic status groups. Beneficiaries enrolled in Medicare Advantage plans, which are managed by private insurance companies, were excluded.

Incident cases from 2015 to 2021:

• decreased from 838,824 to 628,902 in 2021
• had a decrease in the age and sex adjusted incidence rate from 3.5% to 2.8%

Prevalent cases from 2015 to 2021:

• increased from 2,772,188 to 2,875,718 in 2021
• had an increase in age and sex adjusted prevalence from 10.5% to 11.8%

In 2015, men had a higher age standardized incidence rate than women beneficiaries in 2015 (3.5% vs 3.4%), a gap that widened by 2021 (2.9% for men vs 2.6 for women; estimated difference-in-difference 0.94).

Between 2015 and 2021, standardized incidence rates changed among Black individuals (4.2% vs 3.1%), Hispanic individuals (3.7% vs 2.6%), White individuals (3.4% vs 2.8%), and other race/ethnicities (3.1% vs 2.3%).

The difference-in-difference in incidence rates between White and Black individuals was 0.92 (P <.001); between White and Hispanic individuals, 0.88 (P <.001); and between White and other race/ethnicity individuals, 0.93 (P <.001).

Study limitations included the reliance on Medicare claims data influencing diagnostic accuracy, exclusion of patients insured through other mechanisms, and influence of COVID-19 on mortality rates.

“… the burden of dementia was unequally distributed, with the highest incidence and prevalence of dementia among [B]lack beneficiaries and those living in socioeconomically deprived neighborhoods,” the researchers concluded.

Disclosure: Some study authors declared affiliations with biotech, pharmaceutical, and/or device companies. Please see the original reference for a full list of authors’ disclosures.