New estimates state that the incidence of dementia in middle-income countries may be the same as in higher-income countries, according to researchers in the UK.
In addition, the team found that just like in developed countries, education offers substantial protection against dementia in less developed nations. The study is published Online First in The Lancet.
Lead study author Martin Prince from King’s College London said:
“Our studies provide supportive evidence for the cognitive reserve hypothesis that better brain development can mitigate the effects of neurodegeneration in later-life.
Our findings suggest that early life influences, education and learning to read and write, may be particularly important for reducing the risk of dementia in late life. We need to understand more about cognitive reserve, how to measure it, and how it is stimulated across cultures.
The high incidence of dementia in less developed countries remind us that we are facing a global epidemic, and there needs to be more focus on prevention.”
Using conventional western diagnostic approaches, such as the Diagnostic and Statistical Manual of Mental Disorders (DSM) IV criteria, earlier studies have suggested that the incidence of dementia might be significantly lower in low- and middle-income countries vs. high-income nations.
However, the new 10/66 Dementia Diagnosis approach uses methods developed and validated in 25 low and middle-income countries. The new approach has been demonstrated to provide accurate diagnoses even in individuals with little or no education.
In order to the compare the incidence of dementia, and to determine whether education and literacy, among other factors are protective against the development of dementia, the team applied both the standard DSM-IV criteria and the 10/66 approach to around 12,800 individuals aged 65+, across 9 urban and rural sites in Mexico, Cuba, Peru, Venezuela, the Dominican Republic, and China.
The researchers found that the 10/66 dementia incidence is 1.5 – 2.5 times higher than the standard DSM-IV criteria calculated. In addition, 10/66 dementia incidence was consistently comparable to, or high than, dementia incidence reported by earlier studies.
People with dementia at baseline were nearly three times more likely to die than individuals who were dementia-free.
In addition, the team found that 10/66 dementia incidence was linked with low education, being female, and older age.
The researchers conclude, “The protective effects of education seem to extend to settings where many older people have little or no formal education, and literacy confers an additional independent benefit. These findings support the notion that cognitive reserve might counter the effects of neurodegeneration later in life.”
In a joint comment, Kathleen Hall and Hugh Hendrie from Indiana University School of Medicine in the USA, explained:
“The most vexing question posed by Prince and colleagues is that, if the link is substantial, why is incidence of dementia not higher in middle-income countries and even higher in low-income countries than in the high-income countries?
One explanation they suggest is that the high case of mortality associated with dementia in middle-income countries results in an underestimate of incident cases. [But there is another possible explanation] – that low education may simply be a marker for socioeconomic deprivation including poverty, malnutrition, and toxic environmental exposures. These factors, incidentally, have also been implicated as risk factors for dementia.”
Written By Grace Rattue