The trend of an increasing population over 65 years of age in both developed and developing countries leads to an increase in the incidence and prevalence of cognitive disorders, including dementia. Epidemiological studies have estimated the prevalence of dementia in the world population at between 5% and 7%, which is higher in developing countries.

The Declaration made by the United Nations on the Rights of Indigenous Peoples is little known, although it is of great importance from the legal, cultural, and social perspectives [1], which led us to conduct this review of the few studies that exist so far on cognitive disorders and dementia in the indigenous population.

The term "Amerindian" has been named as a translation of the word "Amerindian," which is a compound word that designates all existing populations on the American continent from the Bering Strait to Patagonia before the arrival of the Spaniards.

It has been calculated that approximately 5% of the world's population is represented by the indigenous population, or approximately 370 million people; where more than 70 countries have indigenous populations, such as the United States, Canada, Guam, and Australia, intergenerational difficulties have been described as secondary to colonization, the loss of their culture and traditions, and racial discrimination. It has been found in the literature that there are only 15 studies in which it speaks of the incidence or prevalence of cognitive disorders in the indigenous population; due to the small number of studies, coupled with the high degree of heterogeneity in the sample size of the population studied, geographic location, diagnostic methods, and source of data, as well as the registration of the same, the prevalence range fluctuates between 5 and 20% [2]. 

As the United States becomes a majority-minority nation by 2050, increases in the number of non-Hispanic whites will begin to level off around 2030, while the number of minority populations will continue to grow, particularly among Hispanics, while being lower in the American Indian population [3].

In illiterate older persons, the prevalence is twice as high as in literate persons; in addition, persons with cognitive impairment but no dementia, defined as persons with lower-than-expected cognitive performance but who do not meet the criteria for dementia, are at high risk of developing dementia, showing an annual conversion rate of about 5% to 10%. However, these percentages in ethnically diverse populations, such as indigenous people, are unclear [4].

Pathologies such as hypertension, diabetes, metabolic syndrome, and inactivity have been shown to be risk factors for dementia. A study conducted in a population of 50 Amerindians in Brazil showed a higher prevalence of these pathologies among the indigenous ethnic group studied [5].

Several protective factors for dementia have been described, including cognitive reserve and genetics, among others.

Cognitive reserve (CR) is a construct that is used as an indicator to determine the protective factors in reducing the presentation of neurocognitive disorders, either minor or major. To calculate the CR, multiple measurements have been used for quantification [6]. Culture has been considered an important factor involved in the development and potentiation of cognitive reserve [7], and therefore indigenous culture may have a significant and differential influence on the function Object() { [native code] } of cognitive reserve [8].

Within the literature, an exploratory study of the cognitive reserve was found in the Camentsa Biya community, Sibundoy Valley, Putumayo (Colombia), which documented the prevalence of female gender, most with basic schooling and illiteracy, a moderate correlation was evidenced with the Minimental test and photo test, also their main comorbidities were chronic obstructive pulmonary disease and depression [9].

Fragility syndrome of multiple etiologies, which is characterised by decreased strength, muscular endurance, and reduced physiological function, has been linked to the risk of cognitive impairment [10]. A cross-sectional study with 540 Amerindians over 60 years old in 13 sub-regions of Nario Colombia found a prevalence of 32.4% and a prevalence of 58.7%, respectively, associated with depression and joint pathology [11].

There have been discussions among Amerindians about a protective configuration that may prevent the onset of late-onset Alzheimer's disease (AD), and a possible explanation in the genetic mappings of the Amerindian population could be linked to cultural admixture [12]. Apo-lipoprotein E (ApoE) 4 is the most significant genetic risk factor for late-onset AD; it is elevated in populations such as East Asians, followed by non-Hispanic whites; variation in 4 risk correlates with an ancestral genetic background in an admixture analysis of African American and Puerto Rican populations; Native American populations are underrepresented in genetic studies of AD; in the Peruvian population, approximately 80 percent have Amerindian ancestry.

In a study including 4183 Latin Americans in centers in Bronx, New York, Chicago, Illinois, Miami, Florida, San Diego, and California, the (ApoE) ε4 was documented with a higher incidence in Cubans and Puerto Ricans associated with mild cognitive impairment and AD, in contrast in those of Amerindian genetic ancestry were protected for significant cognitive impairment [14].

For front temporal degeneration (FTD) a study was conducted in Colombia with 132 patients, in which the search for the expansion of the C9ORF72 gene was performed, which presented high frequency in Amerindian genetic markers. [15]. Alzheimer's disease and related dementias are characterized by a decline in memory leading to loss of independence; these diseases have a great impact on patients, families, communities, and health care systems. Alzheimer's disease is the sixth leading cause of death in the U.S. population and the fifth leading cause of death among adults aged 65 years and older, although the primary risk factor for the development of these diseases is age, it appears that race and ethnicity are also important demographic risk factors [16]. Research on dementia disparities is limited by the lack of large, diverse, and representative samples with systematic ascertainment of dementia [3].

In a study conducted on 336 indigenous people over 60 years of age in Kimberly, Western Australia, they found a prevalence of dementia 3–5 times higher than the population living In Australia, in the study group, 45 patients had dementia, and 27 patients in this group had possible AD. Alcohol consumption, head trauma with loss of consciousness, documented depression, high alcohol consumption, social isolation, and reduced physical activity were identified as risk factors for presentation in middle age in the univariate logistic regression analysis [17].

A systematic review of racial and ethnic estimates of Alzheimer's disease and related dementias in the United States (2015-2060) in adults aged 65 years or older who were Medicare fee-for-service beneficiaries discovered that by 2014, 11.5% of patients 65 years had a dementia diagnosis, with the prevalence being higher for women (13.3%) than men (9.2%), increasing as study subjects aged (65 to 74 years at 3.6%, and 75 and older at 5.9%) between 75 and 84 years at 13.6% and  85 years at 34.6%). African Americans had the highest prevalence of related dementias (14.7%), followed by Hispanics (12.9%), non-Hispanic whites (11.3%), Alaska Native American Indians (10.5%), and Asians and Pacific Islanders (10.1%). This review predicts that, in the U.S. population, from 2014 to 2060, cases of Alzheimer's disease and related dementias will see an increase in their total number, reflecting the growth of the ageing population. The Hispanic population will have the largest increase in dementia cases during the projection period. Given the size of the population relative to the other subgroups, the non-Hispanic white population will have the largest total number of cases in all years.

Another systematic review of the literature was conducted to estimate the prevalence and incidence of dementia in U.S. racial and ethnic populations; a total of 1215 studies were examined, of which 114 were included. The reported prevalence rates of dementia for those 65 years and older were 6.3% in Japanese Americans, 12.9% in Caribbean Hispanic Americans, 12.2% in Guamanian Chamorros, and varied widely in African Americans from 7.2% to 20.9% [18]. However, there are no reliable data on the prevalence or incidence of dementia among populations identifying as American Indian or Alaska Native in the United States. The widely dispersed residences of the 180,000 American elders from more than 500 federally recognised tribes on small reservations and villages or integrated into cities across the country make epidemiologic research very challenging. As a result, only a few investigators have attempted to study cognitive status among small samples of American Indian elders, none of which provided prevalence or incidence estimates [19].

Finally, another systematic review of the prevalence of dementia in indigenous populations between 45 and 94 years of age around the world (Indigenous Australians, North Americans, Brazilians, and Canadians) found that it ranged from 0.5% to 26.8% for those over 60 years of age, while prevalence figures for non-dementia cognitive impairment varied in a significant range from 4.4% to 17.7%. Alzheimer's disease was the most common subtype of dementia reported in three of the selected studies. The authors showed that 27.4% of the indigenous sample showed cognitive performance is below cutoff scores on the neuropsychological assessment. Among the non-modifiable factors, age, sex, and genotype were the variables investigated as factors associated with dementia in indigenous peoples. Five of the selected studies showed that high prevalence rates or low cognitive performance were associated with increased age. More than half of the studies reported early onset of cognitive impairment (not dementia but cognitive impairment, not dementia), i.e., before age 65. One study showed an effect of sex on cognitive-performance.

Women performed better than men even when education and health conditions were controlled for in the analysis. In terms of modifiable factors, lower educational attainment and health conditions were associated with high rates of dementia. Poor mobility, head trauma, analgesics, and low body mass index (BMI), measured after the 6.7-year follow-up period, and were associated with cognitive impairment (for dementia as well as non-dementia) in indigenous peoples. During this period, 77% of participants who were initially diagnosed with dementia and 43% of those with non-dementia cognitive impairment died. Another study showed that 38% of American Indians died after an average follow-up period of 2.4 years [4].

Overall, researchers have come to suggest that providing dementia care and support services to ethnic minority service users is challenging, making strategies to overcome cultural and linguistic barriers generally scarce. Communication difficulties, poor knowledge about dementia among ethnic minority service users, inadequate cultural sensitivity of caregivers, and a lack of adequate dementia services for ethnic minority communities are some of the main barriers to be overcome [20]. Ethnic group differences in dementia knowledge and the likelihood of having normalising and stigmatising views of Alzheimer's disease may help explain why some ethnic minority groups are underrepresented in dementia services [21].

Given the literature on cognitive disorders in the Amerindian population, we are currently developing a cognitive profile study in the Wayuu population, an indigenous group in Colombia's northern region.

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