Who develops mild cognitive impairment? What predicts who then develops dementia?

A new study looks at factors that may help predict who will develop thinking and memory problems called mild cognitive impairment, and who will develop dementia among those with mild cognitive impairment. The study is published in the December 1, 2021, online issue of Neurology®, the medical journal of the American Academy of Neurology. Of those who were diagnosed with mild cognitive impairment during the study, researchers found that nearly half were later classified as cognitively normal at their follow-up visit an average of 2.4 years later.

“These results will help us to better understand who is at high risk for dementia so we can identify people for prevention strategies or intervention methods,” said study author Jennifer J. Manly PhD, of Columbia University in New York, NY. “Especially where risk factors can be modified, these results could be important for public health initiatives. The results highlight that mild cognitive impairment is a classification associated with increased risk for progression, but not everyone goes on to develop dementia.”

The study found that having more years of education, taking part in more leisure activities such as reading, visiting a friend or going for a walk as well as having a higher income were predictors of a lower risk of developing mild cognitive impairment. Having a higher number of other medical conditions and having a gene that increases the risk of dementia were predictors of a higher risk of developing mild cognitive impairment.

Among the people with mild cognitive impairment, factors that increased the risk of developing dementia were use of antidepressants, having symptoms of depression, having the gene that increases risk, and having mild cognitive impairment that affects several aspects of thinking skills, such as memory, language, and spatial skills.

The study involved 2,903 people with no thinking or memory problems. Of the group, 31% identified as Black or African American, 43% as Hispanic or Latino, and 27% as White. Also, 40% were evaluated in Spanish.

Participants had an average age of 76 and were followed for an average of 6 years. During that time, 480 people were diagnosed with mild cognitive impairment. To be diagnosed with mild cognitive impairment, people had to meet criteria including: they themselves report that they are having problems with memory or thinking skills; a test shows that they have cognitive impairment; and they are still able to maintain their daily activities, with problems with fewer than three activities such as shopping or handling medications.

Of the people diagnosed with mild cognitive impairment, at a follow-up visit an average of 2 years later, 13% had developed dementia, 30% still met the criteria for mild cognitive impairment and 10% declined in their functioning but did not meet the criteria for mild cognitive impairment or dementia. Another 48% no longer met the criteria for mild cognitive impairment. Of those, people may have had one or two of the three criteria, but not all three. For example, they may have reported memory problems that did not show up on tests or vice versa.

In looking at who was likely to develop mild cognitive impairment, people with more years of education were about 5% less likely to develop mild cognitive impairment. Those with no mild cognitive impairment had an average of 11.5 years of education, compared to 9.9 years for those who developed mild cognitive impairment and 7 years for those who developed dementia.

People who took part in more leisure activities were about 5% less likely to develop mild cognitive impairment. Those with no mild cognitive impairment took part in an average of 7.5 of 13 leisure activities, compared to 7.4 for those who developed mild cognitive impairment and 5.8 for those who developed dementia.

In looking at who with mild cognitive impairment was likely to develop dementia, people who used antidepressants were more likely to develop dementia, with 18% of those who developed dementia using antidepressants, compared to 7% of those who continued with a mild cognitive impairment diagnosis and 6% of those who no longer met the criteria for mild cognitive impairment. Similarly, 21% of those who developed dementia had symptoms of depression, compared to 12% of those who continued with a mild cognitive impairment diagnosis and 10% of those who no longer met the mild cognitive impairment criteria.

Limitations of the study were that the number of people who developed mild cognitive impairment and were available for follow-up was relatively small and the follow-up time was relatively short.

“Future research should investigate the course of mild cognitive impairment across a longer period of time to further dissect which factors can best help us understand the development of dementia,” Manly said. “It should also be noted that these results do not mean that these risk factors cause dementia or will always lead to dementia; they just show an association.”

The study was supported by the Washington Heights-Inwood Columbia Aging Project, National Institute on Aging, National Center for Advancing Translational Sciences and National Institutes of Health.

Source: News Release
American Academy of Neurology
December 1, 2021