The two main forms of dementia—Alzheimer’s disease and vascular dementia—do not affect White and Black people in Brazil in the same way. In both groups, Alzheimer’s disease is the most common cause of cognitive decline with aging. However, it affects a larger proportion of White people than Black people. Vascular dementia, the second most common type, affects a greater percentage of Black people than White people, according to a study led by geriatrician Claudia Suemoto, of the University of São Paulo (USP).
In the study, published in July in the journal JAMA Open Network, Suemoto and colleagues analyzed samples from 16 areas of the brain and other structures of the encephalon from 1,815 individuals with an average age of 74 who died in the city of São Paulo and donated their materials to USP’s Biobank for Aging Studies, one of the largest brain collections in the world. Two-thirds of the donors were White and one-third were Black, with the latter group including Black and mixed-race individuals. When examining the samples under the microscope, the researchers noticed that 28% of the White individuals presented neuritic plaques in the brain tissue, the initial lesions of Alzheimer’s disease, found in 21% of the Black individuals. However, the characteristic damage of vascular dementia, caused by the blockage or rupture of small blood vessels, was observed in 30% of Black individuals and 22% of White individuals.
Of the 1,815 cases evaluated, 747 concentrated lesions in quantities compatible with the diagnosis of dementia. The most common were Alzheimer’s disease (37% of the cases), vascular dementia (26%), and a combination of the two (12%). Among the White individuals with dementia, 39% had Alzheimer’s disease compared to 33% of the Black individuals. In contrast, vascular dementia affected 24% of White individuals and 32% of Black individuals. There was no difference in the frequency of other types of dementia between the two groups.
“We don’t know whether genetic factors may contribute to explaining the difference in the prevalence rates of these forms of dementia, since we did not conduct genetic tests,” says the geriatrician from USP. “The most plausible explanation is that Black people have more vascular dementia because they have less access to health services and inadequate control of cardiovascular risk factors,” he affirms. The Black individuals were younger and had fewer years of formal education than the White individuals. Additionally, a greater proportion of Black individuals smoked, drank large amounts of alcoholic beverages, and had hypertension.
What Suemoto and colleagues are now seeing in a sample of the Brazilian population had only been seen before in the USA. In a study published in 1989 in the Journal of the National Medical Association, pathologist Suzanne de La Monte, of Harvard Medical School, and her colleagues Grover Hutchins (1933–2010) and G. William Moore, of Johns Hopkins University, performed autopsies on 144 dementia patients and verified that Alzheimer’s disease was 2.6 times more common in White individuals than Black individuals. With vascular dementia, the opposite occurred.
More recently, epidemiologist Teresa Filshtein, of the University of California (UC) in San Francisco, and pathologist Brittany Dugger, of UC Davis, evaluated 435 cases of dementia in three ethnic groups: Black, Hispanic, and White non-Hispanic. According to the results published in 2019 in the Journal of Alzheimer’s Disease, the frequency of vascular dementia was greater in the Black ethnic group (40% had the condition) than in the White ethnic group (28%), and even higher in the Hispanic group (54%)—further studies are necessary to explain this increased occurrence of vascular dementia in the Hispanic group.
In addition to corroborating data from the North American population, the Brazilian study is important for at least three reasons. The first is that, with an increasing population and global life-expectancy, a significant rise in dementia cases is expected, especially in middle- and low-income countries, where prevention and access to diagnosis and treatment are more limited.
A forecast published in 2022 in The Lancet Public Health estimates that the total number of people with dementia globally is likely to increase 2.6-fold by 2050, rising from the current 57 million to 153 million. In Brazil, estimates by the group of psychiatrist and epidemiologist Cleusa Ferri, of the Federal University of São Paulo (UNIFESP), published in 2023 in The Journals of Gerontology – Series A, suggest a proportionally greater increase in cases, of 3.3 times in the next decade and a half, rising from 1.8 million to 5.5 million. More recently, the “Relatório nacional sobre a demência” (National report on dementia), released in September, revised these figures upwards. The result of a partnership between UNIFESP and the Brazilian Ministry of Health, as well as the consensus of specialists in the field, the document suggests that the total number of cases was 2.5 million in 2019 and will reach 8.7 million in 2050.
The second reason is because vascular dementia appears to be more common in Brazil than in other countries. In a study published in 2017 in the journal PLOS Medicine, Suemoto and colleagues examined samples of brain tissue from 1,092 individuals and found that, among the cases of dementia, at least 35% were of vascular origin. The average in other countries is 20%.
The third reason is that, according to some experts, cases of vascular dementia may be largely preventable, even more so than other forms of the condition, which include frontotemporal dementia, Lewy body dementia, and Parkinson’s disease dementia (see Pesquisa FAPESP issue nº 329). For this, it is necessary to adequately control the issues that affect the health of the blood vessels, such as diabetes, obesity, high cholesterol, and high blood pressure, among others.
Maintaining good cardiovascular health helps delay cognitive decline—the reduction of memory, concentration, and mental agility—which is exacerbated in dementia. In a study coordinated by Suemoto, researchers from São Paulo, Minas Gerais, and Rio Grande do Sul evaluated four health habits (diet, physical activity, smoking, and sleep quality) and four health indicators (body-mass index, cholesterol levels, glucose levels, and blood pressure) of 11,390 Brazilians. The participants were monitored for eight years and then grouped by a cardiovascular health score. Those who scored highest (between 80 and 100) on this score presented a 42% slower reduction in memory, verbal fluency, and reasoning capacity than those who scored lowest (between 0 and 49 points), mostly Black and mixed-race individuals (55%). According to the results, published in November 2023 in the European Journal of Neurology, the beneficial effect is mainly due to the control of blood sugar (glucose) levels and blood pressure.
Controlling hypertension and diabetes are not the only two factors that can protect against dementia. In its latest report, published in August in the journal The Lancet, the periodical’s Commission for Dementia Prevention, Intervention, and Care, in which Ferri from UNIFESP participates, listed 12 other risk factors that can be modified and, if totally controlled, could prevent 45% of dementia cases (see infographic to the right). In its third edition, the document, produced under the coordination of psychiatrist Gill Livingston, of University College London, in the UK, contained two novelties compared to the previous ones: the reduction of visual acuity and high cholesterol. The 14 identified risk factors can occur at different stages of life, from childhood to old age.
In the early years of life, the modifiable factor that can help protect against dementia decades later is formal education. It aids in the formation of what is known as cognitive reserve, the brain’s capacity to deal with lesions throughout life, possibly because its cells form more connections with each other, and the overall functioning is less impaired by the loss of part of these connections.
The majority of the factors—10 in total—usually manifest or produce an impact in adulthood. They are problems such as hearing loss, depression, high cholesterol, hypertension, and smoking, among others. In old age, the brain becomes more susceptible to the effects of reduced vision, air pollution, and social isolation.
“Although change is difficult and some associations may be only partially causal, our new synthesis of evidence shows how individuals can reduce the risk of dementia,” wrote the authors of the report for The Lancet. According to the researchers, this potential for risk reduction is greater in middle- and low-income countries—and among minority and lower socioeconomic groups—than in higher-income countries.
“In Latin America, for example, besides dementia being more prevalent, its onset occurs earlier than in other countries,” states neurologist Paulo Caramelli, of the Federal University of Minas Gerais (UFMG). He is a coauthor of a study led by neurologist Ricardo Nitrini, of USP, that analyzed studies carried out in six Latin American countries, including Brazil. Published in 2009 in International Psychogeriatrics, the study revealed that, despite the prevalence of dementia in the region being similar to that of developed countries (7.1% of people over 65 years of age had the condition), the proportion of cases was greater at the beginning of old age. In the age range from 65 to 69 years, 2.4% of individuals had dementia in Latin America, while the global average was 1.2%. “We believe that is related to the lack of diagnosis or adequate treatment and control of cardiovascular problems, besides low educational level, which unfortunately is a characteristic of our population,” explains the researcher from UFMG.
In 2022, Caramelli, Suemoto, Ferri, Livingston, and Nitrini recalculated the impact of the 12 risk factors presented in the first editions of the report in The Lancet for the Brazilian reality. If it were possible to eliminate these factors, there would be a 48.2% reduction in dementia cases. The reduction would be as high as 54% in the poorest regions of the country. In the South and Southeast of Brazil, for example, low educational level is associated with 7.7% of the cases, while it is 9.6% in the North, Northeast, and Central-West. Although the avoidable fraction is almost the same for White and Black people (47.9% and 46.9% of cases, respectively), the weight of each factor differs between these two populations (see the infographic below), according to data included in the Ministry of Health’s report and published in November 2022 in Alzheimer’s & Dementia.
Composed of two volumes, the document provides information about stigma associated with dementia, as well as the financial and psychological burden faced by caregivers. It also presents estimates of underdiagnosis, which is 50% in Europe, 60% in the USA, and 80% to 90% in Brazil. “In addition to underdiagnosis, diagnoses are often made very late here,” says Ferri. “Knowing the reality is essential for thinking about action strategies.”
These and other data from the report should guide the implementation of the National Policy for Comprehensive Care for People with Alzheimer’s Disease and Other Dementias, sanctioned by President Luiz Inácio Lula da Silva. Created in accordance with the World Health Organization’s (WHO) Global Action Plan on Dementia 2017–2025, the policy establishes 10 guidelines, covering themes such as strengthening primary health care and training the professionals of these services, creating a care pathway for dementia within existing health programs and services, promoting healthy lifestyle habits aimed at preventing the condition, and ensuring the use of technologies for the diagnosis, treatment, and monitoring of patients. “Several reasons have made the topic of dementia receive more attention in recent years. Now, it is necessary to create strategies that take into account the particularities of the regions and different populations in the country, using the resources we already have and incorporating new ones, in order to carry out prevention, diagnosis, and care for both people with dementia and their caregivers,” highlights Ferri.
The story above was published with the title “Nuances of dementia” in issue 346 of December/2024.
Projects
1. The role of nitric oxide synthases in Alzheimer’s disease (nº 21/14171-8); Grant Mechanism Postdoctoral Fellowship; Supervisor Claudia Kimie Suemoto (USP); Beneficiary Alberto Fernando Oliveira Justo; Investment R$256,435.75.
2. Nosological diagnosis of dementia in the Brazilian population (nº 06/55318-1); Grant Mechanism Regular Research Grant; Principal Investigator Ricardo Nitrini (USP); Investment R$123,173.15.
3. Cognitive reserve in a population with reduced education (nº 09/09134-4); Grant Mechanism Regular Research Grant; Principal Investigator Wilson Jacob Filho (USP); Investment R$61,876.80.
4. Argyrophilic grain disease (nº 12/07526-5); Grant Mechanism Direct Doctoral Fellowship; Supervisor Léa Tenenholz Grinberg (USP); Beneficiary Roberta Diehl Rodriguez; Investment R$46,896.43.
Scientific articles
SUEMOTO, C. K. et al. Neuropathological lesions and cognitive abilities in black and white older adults in Brazil. JAMA Network Open. July 25, 2024.
DE LA MONTE, S. M. et al. Racial differences in the etiology of dementia and frequency of Alzheimer lesions in the brain. Journal of the National Medical Association. June 1989.
FILSHTEIN, T. J. et al. Neuropathological diagnoses of demented Hispanic, Black and non-Hispanic White decedents seen at an Alzheimer’s disease center. Journal of Alzheimer’s Disease. Mar. 12, 2019.
GBD 2019 DEMENTIA FORECASTING COLLABORATORS. Estimation of the global prevalence of dementia in 2019 and forecasted prevalence in 2050: An analysis for the Global Burden of Disease Study 2019. The Lancet Public Health. Vol. 7, no. 2, e105-25. Feb. 2022.
BERTOLA, L. et al. Prevalence of dementia and cognitive impairment in dementia in a large and diverse nationally representative sample: The ELSI-Brazil study. The Journals of Gerontology – Series A. June 2023.
SUEMOTO, C. K. et al. Neuropathological diagnoses and clinical correlates in older adults in Brazil: A cross-sectional study. PLOS Medicine. Mar. 28, 2017.
FERREIRA, N. V. et al. Optimal cardiovascular health is associated with slower cognitive decline. European Journal of Neurology. Nov. 28, 2023.
LIVINGSTON, G. et al. Dementia prevention, intervention, and care: 2024 report of the Lancet standing commission. The Lancet. Aug. 10, 2024.
SUEMOTO, C. K. et al. Risk factors for dementia in Brazil: Differences by region and race. Alzheimer’s & Dementia. Vol. 19, no. 5, pp. 1849–57. Nov. 3, 2022.
Ministério da Saúde. Relatório nacional sobre a demência: Epidemiologia, (re)conhecimento e projeções futuras. 2024.
