In more than 6,000 community dwelling old persons, we examined the relation of education to rate of change in cognitive function during up to 14 years of observation. Level of educational attainment was robustly related to level of cognitive function at study onset. By contrast, we found little evidence that education is associated with cognitive decline. When associations were observed, they were invariably small, with the presence and direction of effects conditional on other variables. In the context of previous work, the findings suggest that education affects risk of late life dementia primarily by virtue of its association with level of cognition and not by an association with rate of cognitive decline.
A simple tally of prior research tends to support an association between higher educational attainment and reduced cognitive decline, with nearly half of published studies reporting the association,5–11,13–15,22,23
and about one quarter finding mixed evidence of it.12,16–21
In the negative studies,25–28,37,38
however, change was more likely to be based on three or more cognitive assessments rather than only two (4/8 vs 2/19, p
= 0.059, Fisher exact test) and on 6 or more years of observation rather than less than 6 (5/11 vs 0/14, p
= 0.003, Fisher exact test). Further, in each of three projects that published two articles on education and cognitive decline, education was related to cognitive decline in the earlier publication,15,21,22
but not in the later publication despite additional data collection.25,26,28
In research with three or more assessments of cognition, evidence linking higher level of education with reduced cognitive decline has been limited, with four studies reporting no association25–28
and four finding it to be conditional on some other variable (e.g., sex,12
). In short, the studies best equipped to assess change in cognitive function, by virtue of measuring it more often during a longer period of time, were the least likely to find an association with education. This is the opposite of the pattern that one would expect if education were truly related to change in cognitive function. Instead, we propose that education has little or no association with change in cognition and that evidence to the contrary mainly reflects difficulty disentangling level of cognition, which is robustly related to education, from change.
Little is known about education and cognitive decline in black persons.39
In this biracial population, the association of education with cognitive decline was comparable in black and white participants.
Repeated administration of cognitive tests leads to improved performance,33,34
and such retest effects might influence the association of education with cognitive change.27
One prior study did find that lower education was associated with greater improvement from the first to second testing and that after controlling for this apparent retest effect, higher education predicted less cognitive decline during the remainder of the study.21
However, cognitive retest effects are known to persist beyond a single retesting34
and education was not related to retest effects across the range of follow-up in this population, consistent with previous research.34
There was a differential effect of the first observation, but deleting it eliminated education’s association with cognitive change rather than enlarging it.
Because education’s association with change in cognitive function may shift as impairment in cognition begins to emerge,40
the presence of cognitive impairment within a cohort might obscure a protective effect of education. In this population, however, excluding persons with low cognitive function at baseline did not have this effect: although higher education was associated with reduced cognitive decline in the early years of follow-up, it was associated with more rapid decline in later years.
Confidence in these findings is strengthened by several factors. First, they are based on a geographically defined and racially diverse population of older persons. Second, the availability of a psychometrically sound composite measure of cognition administered at regular intervals with high follow-up participation in survivors enhanced our ability to reliably assess individual differences in rate of cognitive change and their relation to education. Finally, the long follow-up period enhanced our ability to distinguish initial level of cognition from rate of change, and the large cohort size made it possible to identify even small effects.
This study also has important limitations. Because results are based on a measure of global cognition, we cannot rule out the possibility that education is related to decline in some cognitive domains but not others. In addition, the measure of educational attainment, years of schooling, assumes an equivalence of educational quality across persons and time that is unlikely to be true. Incorporating data on educational quality (e.g., spending per pupil in county) with amount of schooling might provide further insight into the association of education with age-related cognitive decline.