06.02.01. What is the estimated prevalence and incidence of dementia and the source of these estimates? | Mexico

06.02.01. What is the estimated prevalence and incidence of dementia and the source of these estimates? | Mexico

13 Jul 2022

Since 2003, two national health surveys and two dementia specific surveys have documented the prevalence of dementia and cognitive impairment in Mexico.

1. Mexican Health and Aging Study, MHAS (Encuesta Nacional de Salud y Envejecimiento en México, ENASEM, mhasweb.org).

The initiative is funded by the National Institute of Health and the National Institute of Aging of the United States. This is the first large scale longitudinal study in Mexico with data collected in 2001 (baseline study) with follow-up interviews in 2003, 2012, 2015 and 2018 (Wong et al., 2015). The objective of this longitudinal study is to prospectively evaluate the impact of diseases, functioning and mortality of adults 50 years of age and older (or adults born in 1951 or earlier at the time of the baseline survey), in more and less urban areas of Mexico. In MHAS, the identification of cases of dementia was made using an algorithm based on a cognitive evaluation (performed with a battery of instruments) and another on functional ability. The prevalence of dementia estimated in a report of 2011 was 5.2%, adjusted for age and schooling (Mejía-Arango et al., 2011).

2. National Health and Nutrition Survey ENSANUT 2012 (Encuesta Nacional de Salud y Nutrición, https://ensanut.insp.mx/).

The National Survey of Health and Nutrition (ENSANUT) is a probabilistic, multi-phase survey designed to estimate the prevalence of health conditions, nutrition, and its determinants, in nationally representative samples of children 0 to 11 years of age, adolescents 12 to 19 years old, adults 20 to 59, and older adults (60+ years). It has a representative sample design at the national, state, urban and rural stratum (Romero-Martinez et al., 2013). The module for the evaluation of older adults was first added in 2012 and included a sample of 8,874 adults aged 60 or older. Two instruments were used for dementia diagnosis: a battery to assess cognitive functioning (semantic verbal fluency the Mini-cog) and the evaluation of functional ability. These were used to construct a diagnostic algorithm. People who presented alteration in both cognitive ability and functional ability were considered to have dementia. This resulted in an estimated dementia prevalence of 7.9% for the total of older adults’ sample (Manrique Espinoza et al., 2013). In relation to distribution of dementia across the country, Acosta-Castillo et al., (2017) report the prevalence of dementia by state and level of deprivation, and report adjusted prevalence of dementia (by sex, age and education) of 8.0% at national level, ranging from 3.3% in Querétaro to 12.5% in Jalisco, and from 3.9% in people between 60-69 years and 20.6% in the group aged 80 years or more. The prevalence is similar in some levels of deprivation (around 8.0%), except in those areas with high and very high deprivation (11.1%). They report that of the almost 900,000 people living with dementia in Mexico, more than half have experienced food insecurity and about 200 thousand live in localities with high and very high levels of deprivation. This demonstrates great variability in the prevalence of dementia by state and suggests that many people affected by dementia experience high levels of vulnerability.

3. Dementia Research Group 10/66 study (https://www.alz.co.uk/1066/).

The 10/66 Dementia Research Group research programme was developed to address the dementia prevalence, incidence, and impact across Latin American countries, China and India, using a validated and common methodology in a multi-centric population of adults aged 65 years and over (Prina et al., 2017). Data have been obtained on the prevalence and impact of dementia, and on incidence (phase 2007-2010), which evaluated the incidence of dementia and some associated risk factors, as well as mortality, with a median follow-up of 3 years (Prince et al., 2012). The case identification of dementia is carried out using two algorithms, one that operationalizes the criteria for dementia of the DSM-IV, and another that is developed by the 10/66 group (Prince et al., 2003). A case is considered positive for dementia if either of the two criteria is positive. The prevalence of dementia is of 8.6% in the urban area, compared to 7.4 in the rural area. However, the standardised prevalence (95% CI) using the 10/66 algorithm is 7.4% (5.9-8.9) in Mexico in urban areas, and 7.3% (5.7-8.9) in rural areas. The standardised prevalence according to DSM-IV criteria is 3.2% (2.2-4.2) in Mexico urban, and 2.4% (1.2-3.6) (Llibre et al., 2008).

4. Survey of the Metropolitan Area of Guadalajara.

In 2014, a cross-sectional study was conducted on a population aged 60 years or above, living in the state of Jalisco (in the Western region of the country). A total of 1,142 people participated. Participants were selected through multiple probability random sampling and door-to-door interviewing. All participants were evaluated for their cognitive function, emotional state, and physical performance. Cognitive function, depression and functional disability were assessed using the Mini-Mental State Examination (Folstein et al., 1975), the geriatric depression scale and the Katz index, respectively. The diagnosis of dementia was made according to the DSM-IV criteria. The prevalence of dementia was 9.5% (63.35% of women and 36.7% of men) (Velázquez-Brizuela et al., 2014).

Table 11 shows prevalence data of dementia. Variations may be due to the use of different classifications, forms and extensions of cognitive assessments and assessment of limitations in functionality. For example, while ENSANUT and MHAS/ENASEM only assess dementia with cognition and loss of function (assessed through altered activities of daily living); in 1066 DSM-IV criteria are operationalised and the algorithm is tested against these criteria, not only against the sum of cognitive impairment and loss of functionality. 

Table 11. Population studies, prevalence data of dementia.

Study Evaluation criteria Sample size Adjusted prevalence, total or subgroups

(Mejía- Arango et al., 2011)

Cognitive evaluation and functional limitations (CCCE, difficulty in performing daily activities 7,166 community-dwelling adults, 60 years and older 6.1
Dementia Research Group 10/66

(Llibre et al., 2008)

10/66 Algorithm and DSM IV Criteria 1,003 urban and 1,000 rural community-dwelling adults, 65 years and older Urban 8.6

Rural 8.5

Survey of the Metropolitan Area of Guadalajara (Encuesta del Área Metropolitana de Guadalajara)

(Velázquez-Brizuela et al., 2014)

DSM-IV 1,142 older adults, 60 years and older 9.5
National Health and Nutrition Survey ENSANUT 2012

(Manrique Espinoza et al., 2013)

Cognitive evaluation and functional limitations 8,874 older adults, 60 years and older 7.9

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