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TOPLINE:

The proportion of dementia cases that were undiagnosed was high in the US and Brazil in a new cohort study, but the percentage was markedly higher in Brazil (76% vs 45%). Undiagnosed dementia was also associated with increased 4-year mortality compared to no dementia in both countries.

METHODOLOGY:

• Researchers conducted a longitudinal observational study using data for more than 9500 participants (mean age, 75 years; 86% White individuals) in the 2016 US Health and Retirement Study and more than 3600 participants (mean age, 73 years; 43% White individuals) in the 2015-2016 Brazilian Longitudinal Study of Aging to determine the prevalence of undiagnosed dementia in adults at least 65 years of age.
• All participants were classified as having no dementia, undiagnosed dementia, or diagnosed dementia.
• Factors evaluated included sociodemographic characteristics, health comorbidities, self-rated health, geriatric conditions, and healthcare access and use.
• Mortality was assessed in follow-ups through 2020 using cohort-specific sources.

TAKEAWAY:

• The proportion of undiagnosed dementia was 45% in the US and 76% in Brazil, with similar dementia prevalences (7.9% vs 8.0%, respectively).
• The cumulative 4-year mortality rate was lower for undiagnosed dementia than for diagnosed dementia in the US (10% vs 14%; P = .003), whereas it did not differ significantly between the groups in Brazil. However, mortality rates were higher among participants with diagnosed or undiagnosed dementia than those without dementia in both countries.
• After adjustment for sociodemographic and clinical factors, undiagnosed dementia was also associated with higher risk for mortality compared with no dementia in both the US and Brazil (hazard ratios, 1.9 and 1.8, respectively).
• Younger age and an absence of memory complaints were associated with undiagnosed dementia in both countries. Additional factors linked to undiagnosed dementia were frailty and hearing impairment in the US; and Asian or Indigenous race or ethnicity, fewer years of education, rural residence, and lower use of specialist care in Brazil.

IN PRACTICE:

“Undiagnosed dementia is common and associated with increased mortality, identifying a vulnerable population missed by current diagnostic pathways,” the investigators wrote.

“As global populations age and the number of people living with dementia increases, these cross-national differences support efforts to improve timely, equitable detection and access to postdiagnostic care, particularly in lower-resource settings,” they added.

SOURCE:

This study was led by Marlon Juliano Romero Aliberti, MD, PhD, Hospital das Clinicas HCFMUSP, Universidade de Sao Paulo, São Paulo, Brazil. It was published online on April 29 in Alzheimer’s & Dementia.

LIMITATIONS:

Comparison across countries may have been affected by differences in measurement and healthcare, including variations in how reported diagnoses were ascertained across cohorts. The dementia classification relied on validated survey algorithms based on cognitive and functional performance rather than clinical diagnosis. The cognitive battery did not capture all domains, particularly visuospatial and executive function, and the study lacked linkage to administrative health records. Additionally, self- or proxy-reported diagnosis of dementia probably reflected limited awareness rather than the absence of a diagnosis.

DISCLOSURES:

This study was funded by the Fundação de Amparo à Pesquisa do Estado de, São Paulo, Conselho Nacional de Desenvolvimento Científico e Tecnológico, the National Institute on Aging, and the Alzheimer’s Association. The investigators reported having no relevant conflicts of interest.

This article was created using several editorial tools, including AI, as part of the process. Human editors reviewed this content before publication.