Objectives: Despite the increasing number of people with dementia (PWD), detection remains low worldwide. In Brazil, PWD is expected to triple by 2050, and diagnosis can be challenging, contributing to high and growing rates of underdiagnosis. At the moment, there is no national estimate of the under detection or characteristics of its distribution according to gender, age and region. We aimed to estimate the proportion of PWD not diagnosed in relation to the estimated number of PWD.

Methods: The number of diagnosed individuals were estimated based on national records of the prescription of anticholinesterases drugs (AChE) in 2022 for the treatment of mild and moderate stages of Alzheimer’s Disease (AD) held by the Unified Health System (SUS). Data were obtained from ftp://ftp.datasus.gov.br and drugs were dispensed according to the national clinical protocol. Studies from the national literature were consulted to estimate: (i) the number of people currently diagnosed with mild and moderate AD; (ii) the proportion of those who obtain AChE from SUS; (iii) the proportion of those who do not take AChE; and (iv) the proportion of AD related to other dementias. We assumed that the under-detection rate of AD would be similar to other dementias and 70% of the diagnosed AD individuals obtain AChE from SUS.

Results: More than 80% of the PWD 60+ are undetected (88.7%, 95% CI = 88.6–88.7). The poorest regions had higher rates (94.6% 95%, CI = 94.5–94.6) than the richest (84.8%, 95% CI = 84.7–84.8). Men had higher rates (89.8%, 95% CI = 89.7–89.9) than women (87.4%, 95% CI = 87.4–87.5). The youngest age group (60-64) had the highest rate (94.6%, 95% CI = 94.5–94.7) which decreased until 85–89 (84.3%, 95% CI = 84.2–84.4), before increasing again to 91.1% (95% CI = 91.0–91.2) among 90+.

Conclusions: Dementia under detection in Brazil is among the highest in the world. Fast populational aging and the highest rates among the youngest individuals are of concern as it may be related to late diagnosis. Gender and regional disparities also need to be considered when developing health policies.