Higher levels of education did not delay the onset or modify the progression of dementia in a longitudinal clinical-pathologic cohort study, adding fuel to the discussion about the role of cognitive reserve in aging.
While prior research has suggested that education may provide a “cognitive reserve” that buffers against dementia, this study showed that years of schooling were tied to higher cognition levels at baseline, but not to slower rates of cognitive change in old age, reported Robert Wilson, PhD, of Rush University Medical Center in Chicago, and colleagues in Neurology.
“This finding that education apparently contributes little to cognitive reserve is surprising, given that education affects cognitive growth and changes in brain structure,” Wilson said in a statement. “But formal education typically ends decades before old age begins, so late-life activities involving thinking and memory skills such as learning another language or other experiences such as social activities, cognitively demanding work, and having a purpose in life may also play a role in cognitive reserve that may be more important than remote experiences such as schooling.”
“Of course, even if one declines at the same rate, it is still better to start at a higher level of cognition,” he added.
Level of education has been used widely as an indicator of cognitive reserve. Several studies have shown the protective effects of higher education levels on dementia, but evidence is mixed.
The problem may be with using education as a proxy for cognitive reserve, noted George Rebok, PhD, of Johns Hopkins University in Baltimore, who was not part of the study. “The idea of education being somehow a ‘cognitive vaccine’ you get early in life that confers protective benefit throughout the life course is something we need to examine,” he told MedPage Today.
“There are so many different metrics and ways to think about education,” Rebok added. Most research looks at formal education, but “that doesn’t address aspects like quality of education, continuity of education, or types of education. It also doesn’t say anything about informal education that people might seek out on their own.”
In this study, Wilson and colleagues looked at data collected from 1994 to 2018 in two cohorts: the Religious Orders Study of older Catholic clergy members throughout the U.S. (n=1,239), and the Rush Memory and Aging Project of older people in metropolitan Chicago (n=1,660). In both cohorts, participants had annual cognitive testing and agreed to brain autopsy at death. Cognitive test scores were converted to a standard scale and averaged to produce composite cognition measures.
The 2,899 participants had a mean age of 78 at baseline and an average of 16.3 years of education. They were followed for an average of 8 years; 88.6% were white and 73.9% were women. The researchers evaluated three subgroups: people who developed incident dementia (n=696); people who died and had a neuropathologic examination (n=752); and people in both categories (n=405).
Across all participants, education was associated with initial level of global cognition, but not with slower rates of cognitive change.
Among people who developed dementia, the rate of global cognitive decline accelerated a mean of 1.8 years before dementia diagnosis; among people who had died, it accelerated a mean of 3.4 years before death. In both groups, education was not linked to the onset or to a slower rate of linear cognitive decline.
Higher education was associated with lower likelihood of gross and microscopic cerebral infarcts, but not other postmortem markers. In individuals with neurodegenerative or cerebrovascular conditions, education did not modify their cognitive trajectories.
“This is a thorough and impressive study that is a significant contribution to the literature and supports the notion that intellectual endeavor during early and mid-life produces a life-course advantage, but does not influence the rate of decline in old age,” observed Roger Staff, PhD, of the University of Aberdeen in Scotland, who was not involved with the study.
“These studies are difficult to perform requiring great effort over long periods of time,” Staff told MedPage Today. “This data is about as good as it gets; the analysis is precise and appropriate and the results meaningful.” But while the Religious Order cohort “has produced some significant works over the years, I do have some minor concerns over the generalizability of such a sample,” he said.
One limitation is that participants had a relatively high level of education, Wilson added, and it’s possible that relationships between education and dementia seen in earlier studies were driven by variations at the lower end of the education level spectrum.
The study was supported by the NIH and the Illinois Department of Public Health. The researchers disclosed support from the NIH.