new research shows.
The investigators found individuals with these factors, which are all markers of cognitive reserve, had a significantly greater chance of reversion from MCI to normal cognition (NC) than progression from MCI to dementia.
In a cohort study of more than 600 women aged 75 years or older, about a third of those with MCI reverted to NC at some point during follow-up, which sends “an encouraging message,” study author Suzanne Tyas, PhD, associate professor, University of Waterloo (Ont.), said in an interview.
“That’s a positive thing for people to keep in mind when they’re thinking about prognosis. Some of these novel characteristics we’ve identified might be useful in thinking about how likely a particular patient might be to improve versus decline cognitively,” Dr. Tyas added.
The findings were published online Feb. 4, 2022, in the journal Neurology.
Highly educated cohort
As the population ages, the number of individuals experiencing age-related conditions, including dementia, increases. There is no cure for most dementia types so prevention is key – and preventing dementia requires understanding its risk factors, Dr. Tyas noted.
The analysis included participants from the Nun Study, a longitudinal study of aging and cognition among members of the School Sisters of Notre Dame in the United States. All were 75 and older at baseline, which was from 1991 to 1993; about 14.5% were older than 90 years.
Participants were generally highly educated, with 84.5% attaining an undergraduate or graduate degree. They also had a similar socioeconomic status, level of social supports, marital and reproductive history, and alcohol and tobacco use.
Researchers examined cognitive function at baseline and then about annually until death or end of the 12th round of assessments. They used five measures from the Consortium to Establish a Registry for Alzheimer’s Disease neuropsychological battery to categorize subjects into NC, MCI, or dementia: Delayed Word Recall, Verbal Fluency, Boston Naming, Constructional Praxis, and the Mini-Mental State Exam.
The current analysis focused on the 619 participants with data on apolipoprotein E (apo E) epsilon-4 genotyping and education. From convent archives, investigators also had access to the nuns’ early high school academic performance in English, Latin, algebra, and geometry.
“Typically we only have data for [overall] education. But I know from teaching that there’s a difference between people who just pass my courses and graduate with a university degree versus those who really excel,” Dr. Tyas said.
The researchers also assessed handwriting samples from before the participants entered the religious order. From these, they scored “idea density,” which is the number of ideas contained in the writing and “grammatical complexity,” which includes structure, use of clauses, subclauses, and so on.
Dementia not inevitable
Results showed 472 of the 619 participants had MCI during the study period. About 30.3% of these showed at least one reverse transition from MCI to NC during a mean follow-up of 8.6 years; 83.9% went on to develop dementia.
This shows converting from MCI to NC occurs relatively frequently, Dr. Tyas noted.
“This is encouraging because some people think that if they have a diagnosis of MCI they are inevitably going to decline to dementia,” she added.
The researchers also used complicated modeling of transition rates over time between NC, MCI, and dementia and adjusted for participants who died. They estimated relative risk of reversion versus progression for age, apo E, and potential cognitive reserve indicators.
Not surprisingly, younger age (90 years or less) and absence of apo E epsilon-4 allele contributed to a significantly higher rate for reversion from MCI to NC versus progression from MCI to dementia.
However, although age and apo E are known risk factors for dementia, these have not been examined in the context of whether individuals with MCI are more likely to improve or decline, said Dr. Tyas.
Higher educational attainment, the traditional indicator of cognitive reserve, was associated with a significantly higher relative risk for reversion from MCI to NC versus progression from MCI to dementia (RR, 2.6) for a bachelor’s degree versus less education.
There was a greater RR for even higher education after adjusting for age and apo E epsilon-4 status.
Language skills key
Interestingly, the investigators also found a significant association with good grades in high school English but not other subjects (RR for higher vs. lower English grades, 1.83; 95% confidence interval, 1.07-3.14).
In addition, they found both characteristics of written language skills (idea density and grammatical complexity) were significant predictors of conversion to NC.
“Those with high levels of idea density were four times more likely to improve to normal cognition than progress to dementia, and the effect was even stronger for grammatical structure. Those individuals with higher levels were almost six times more likely to improve than decline,” Dr. Tyas reported.
The RR for higher versus lower idea density was 3.93 (95% CI, 1.3-11.9) and the RR for higher versus lower grammatical complexity was 5.78 (95% CI, 1.56-21.42).
These new results could be useful when planning future clinical trials, Dr. Tyas noted. “MCI in some people is going to improve even without any treatment, and this should be taken into consideration when recruiting participants to a study and when interpreting the results.
“You don’t want something to look like it’s a benefit of the treatment when in fact these individuals would have just reverted on their own,” she added.
Research implications
Commenting on the findings, Claire Sexton, DPhil, director of scientific programs and outreach at the Alzheimer’s Association, noted that, in “this study of highly educated, older women,” transitions from MCI to NC “were about equally common” as transitions from MCI to dementia.
“As advances are made in early detection of dementia, and treatments are developed and marketed for people living with MCI, this article’s findings are important to inform discussions of prognosis with patients and [to the] design of clinical trials,” Dr. Sexton said.
The study was funded by the Canadian Institutes of Health Research and the Natural Sciences and Engineering Research Council of Canada. Funding for the Nun Study at the University of Kentucky was provided by the U.S. National Institute of Aging and the Kleberg Foundation. Dr. Tyas has disclosed no relevant financial relationships.
A version of this article first appeared on Medscape.com.