ABSTRACT Objective To estimate the national proportion of undiagnosed dementia cases in Brazil, examine its distribution across Brazilian regions sociodemographic subgroups, and identify factors associated with receiving a diagnosis. Methods We conducted a cross‐sectional, population‐based analysis using baseline data (2015–2016) from the Brazilian Longitudinal Study of Aging (ELSI‐Brazil), a nationally representative survey of community‐dwelling adults. Dementia was identified through an established algorithm incorporating cognitive testing and functional impairment, combined with self‐reported medical diagnosis of Alzheimer's disease. Underdiagnosis was defined as meeting dementia criteria without a prior medical diagnosis. Sociodemographic, clinical, cognitive, and functional variables were assessed. Survey‐weighted logistic regression models estimated factors associated with underdiagnosis. Results Among 5249 participants aged ≥ 60 years, 392 met criteria for dementia. Overall, 83.1% (95% CI: 76.5–88.1) had no previous diagnosis. Underdiagnosis was more frequent in poorer regions (90.2%) than in richer regions (76.0%), and higher among illiterate individuals (93.9%). In fully adjusted models, older age (OR = 0.91; 95% CI: 0.85–0.97), more years of education (OR = 0.86; 95% CI: 0.76–0.96), a higher number of chronic conditions (OR = 0.72; 95% CI: 0.54–0.97), and better memory performance (OR = 0.68; 95% CI: 0.56–0.84) were associated with a lower likelihood of underdiagnosis, while living alone was associated with a higher likelihood of underdiagnosis (OR = 3.65 1.05–12.6). Conclusions About four in five older Brazilians meeting dementia criteria had no prior clinical diagnosis, with marked sociodemographic and regional disparities. Both individual factors—such as age, education, and multimorbidity—and structural inequities across regions influenced diagnostic likelihood. Strengthening early‐detection strategies, improved health professional training, and regionally tailored approaches may improve recognition of dementia in Brazil's public health system.
Miguel et al. (Wed,) studied this question.