A large new study is highlighting a link between mild cognitive impairment, physical disability and psychological symptoms such as anxiety.
As populations in low and middle-income countries are aging, rates of dementia are rising, say Dr. Robert Stewart of King’s College London, UK, and colleagues in the journal PLoS Medicine. Currently, more than 35 million people worldwide have dementia, the majority of which is Alzheimer’s disease. More than 115 million people may have dementia by the year 2050, with much of this rise occurring in low- and middle-income countries.
“Mild cognitive impairment is a construct frequently used to define groups of people who may be at risk of developing dementia,” explain Dr. Stewart and colleagues. “It can be seen as an intermediate state between normal cognitive aging and dementia.”
People with mild cognitive impairment have problems that are more severe than those normally seen in people of a similar age, such as misplacing things and forgetting appointments, but they have no other symptoms of dementia and are able to look after themselves. The condition is currently defined as “a syndrome with impairment of memory or another cognitive deficit that does not interfere substantially with personal affairs nor result in inability to live independently.”
Knowing a country’s rates of mild cognitive impairment is crucial for helping governments plan their future health care and social support needs, but the rates in low- and middle-income countries are largely unknown.
The research team analyzed survey findings on 15,376 people ages 65 years or older without dementia living in Cuba, Dominican Republic, Peru, Mexico, Venezuela, Puerto Rico, China, and India.
Mild cognitive impairment was associated with physical disability, anxiety, apathy, and irritability, but not depression. It was not linked to age or education. Men had a slightly higher rate of mild cognitive impairment than women. This finding contrasts with higher reported rates of dementia among women than to men, but could be explained by the exclusion of confirmed dementia cases. Experts from the Mayo Clinic, Rochester, Minn., say that women may move from normal cognition directly to dementia at a later age but more abruptly.
Rates of mild cognitive impairment varied more than five-fold between countries, from 0.8 percent in China to 4.3 percent in India, but the authors think this mainly reflect difference in the diagnostic tests used.
The authors conclude that mild cognitive impairment “was consistently associated with higher than expected disability and neuropsychiatric symptoms.” But they add that longer-term figures are needed to confirm the findings, in particular, to investigate the factors that may protect against progression to dementia.
“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 write.
They point out that the large numbers of individuals affected “will have significant implications with regard to social support and future health care costs, especially as systems are not in place to cope with increased neurodegenerative disease and health resources at present are already extremely limited.”
Findings such as these are helping “build an evidence base to inform the development and implementation of policies for improving the health and social welfare of older people in low- and middle-income countries.”
A review carried out in 2008 also found that mild cognitive impairment is associated with these symptoms, which the researchers believe are of “potential importance for defining subgroups at higher risk of developing dementia in the future.”
In the review, Liana G. Apostolova, MD, of the University of California-Los Angeles (UCLA), explains that “behavioral abnormalities may prove to be a valuable biomarker for impending dementia.” They looked at the published evidence and found that behavioral abnormalities are reported in 35 to 75 percent of mild cognitive impairment patients, with the most common being apathy, anxiety and irritability. In addition, the researchers found evidence of a link with depression.
“There is a compelling body of evidence that mild cognitive impairment patients with behavioral features are more prone to develop Alzheimer’s disease than patients without these features,” they write in the journal Dementia and Geriatric Cognitive Disorders.
“The behavioral changes observed in mild cognitive impairment are similar to those of Alzheimer’s disease, and may help identify the subgroup of mild cognitive impairment patients with early Alzheimer’s disease,” they conclude.
Some of the risk factors for mild cognitive impairment and dementia are: physical inactivity, infrequent participation in mentally or socially stimulating activities, high blood pressure, diabetes, and smoking.
Sosa, A. L. et al. Prevalence, Distribution, and Impact of Mild Cognitive Impairment in Latin America, China, and India: A 10/66 Population-Based Study. PLoS Medicine February 8, 2012 doi:10.1371/journal.pmed.1001170
Apostolova, L. G. and Cummings, J. L. Neuropsychiatric Manifestations in Mild Cognitive Impairment: A Systematic Review of the Literature. Dementia and Geriatric Cognitive Disorders Vol. 25, No. 2, February 2008, pp. 115-26. doi:10.1159/000112509