In low- and middle-income countries, mild cognitive impairment -- an intermediate state between normal signs of cognitive aging, such as becoming increasingly forgetful, and dementia, which may or may not progress -- is consistently associated with higher disability and with neuropsychiatric symptoms but not with most socio-demographic factors, according to a large study published in this week's PLoS Medicine.
The established 10/66 Dementia Research Group interviewed approximately 15 000 people over 65 years of age who did not have dementia in eight low- and middle-incomes countries: Cuba, Dominican Republic, Peru, Mexico, Venezuela, Puerto Rico, China, and India.
Participants also completed standardized assessments of their mental and physical health and cognitive function and the researchers also interviewed relatives and carers for further details about any memory loss or other declines in cognitive function or the presence of any neuropsychiatric symptoms.
Then, using a clinical framework and a statistical model, the authors found that mild cognitive impairment with related memory problems was associated with disability, anxiety, apathy, and irritability but not with depression.
Increasing age or former education level did not seem to be linked but the authors found that men had a slightly higher prevalence of mild cognitive impairment than women. Furthermore, the prevalence of this type of mild cognitive impairment ranged from 0.8% in China to 4.3% in India.
The authors say: "This is one of the first studies, to our knowledge, to investigate the prevalence of [mild cognitive impairment with related memory problems] in [low- and middle-income countries], where the large majority of older people and people with dementia currently live."
They continue: "Differences in prevalence between countries were marked and ranged from 0.8% (China) to 4.3% (India), that is, greater than fivefold variation. After direct standardization for age, gender, and education, using the whole population as the reference, these differences were not markedly attenuated."
The authors conclude: "Further evaluation is needed of the associations with disability and neuropsychiatric symptoms since our findings do suggest higher than expected comorbidity and there are large absolute numbers of older people with [mild cognitive impairment with related memory problems] in these rapidly ageing and populous world regions."
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