BOSTON—Higher education is associated with a slower rate of functional decline in patients with mild functional impairment, researchers reported at the 2012 Annual Meeting of the American Neurological Association. However, after a patient reaches a particular threshold in the disease process, education loses its protective effects.
“These results support the potential protective effects of education to facilitate a functional reserve that is above and beyond cognitive ability and may be particularly effective in earlier stages of Alzheimer’s disease,” said Meghan B. Mitchell, PhD, Research Fellow in Neurology at the Massachusetts General Hospital in Boston, and colleagues.
Cognitive Reserve Revisited
The effect of education on the rate of dementia progression has been widely debated, as some studies have suggested that education is associated with concurrent level of cognitive function but does not affect the rate of decline. Proponents of the cognitive reserve hypothesis argue that persons with greater educational achievement have better cognitive function than those with less education in the presence of elevated fibrillar brain amyloid levels.
A total of 1,026 patients with probable Alzheimer’s disease underwent multiple evaluations and treatment for dementia. All participants had five or more years of education, a Hachinski Ischemia Scale score of 4 or lower, a final diagnosis of probable Alzheimer’s disease at last study visit, and they were not taking antipsychotic medications. Using mixed effects modeling, the researchers examined the effect of education level on the trajectory of functional decline, per score on the Weintraub Activities of Daily Living scale. Models were adjusted for baseline levels of cognitive performance and activities of daily living function and their interactions with time.
The mean baseline age of participants was 73.5, and the mean education level was 13.7 years. About 62% were women, and the average age of disease onset was 70.2.
Higher Education Linked to Slower Functional Decline
The researchers found an overall relationship between education level and activities of daily living function, both cross-sectionally and longitudinally. Within models that accounted for the level of baseline functional impairment, higher education was associated with a slower rate of decline in patients with mild functional impairment.
“The relationship between education and functional decline varies by baseline level of functional impairment,” commented Dr. Mitchell. “In individuals with low functional impairment, education appears to be protective. However, in individuals with more functional impairment at baseline, higher education is no longer protective.”
In advanced stages of Alzheimer’s disease, according to the cognitive reserve hypothesis, patients with a high education level will reach a tipping point, “after which they have a more precipitous decline than their less educated counterparts,” noted Dr. Mitchell. “While our models were not designed to test the threshold of a late dominating nonlinear effect, our model did predict a slightly faster decline in individuals with higher education who have significant levels of functional impairment at baseline.”
Dr. Mitchell said that her team’s findings extend the reserve hypothesis by introducing the concept of functional reserve and “suggest that education has a protective effect on daily function that may be sustained for a longer period of time relative to its effect on cognitive performance.”