Scientists have long debated why there seems to be an association between higher levels of education and lower rates of Alzheimer's disease in later life. New research from Johns Hopkins Medicine is suggesting neurodegenerative disease is just as prevalent in more-educated individuals but a greater cognitive reserve can temporarily mitigate the impact of Alzheimer's pathology in one's senior years.

Prior studies have consistently uncovered a correlation between higher education and lower rates of dementia, however it has been unclear whether this link was related to actual structural differences in the brain, or if it simply was a case of more education giving individuals a kind of cognitive head start. To investigate this distinction researchers looked at data from a study following thousands of subjects for several decades, from mid-life to later-life.

The study homed in on 331 subjects who all underwent brain imaging to evaluate levels of amyloid beta in the brain, the main pathological characteristic associated with the onset of Alzheimer's disease. Alongside this, the subjects were cognitively tested several times over a 20-year period to track any decline.

Interestingly, the research revealed that education level has no association with the rate of pathological progression in Alzheimer's disease. So, regardless of a person's level of education, be it less than high school or all the way up to college, the progression of amyloid beta were the same. However, cognitive testing revealed a distinct correlation between education levels and intellectual function, despite amyloid beta accumulations in the brain. This means college educated subjects performed better on cognitive tests in later years compared to subjects with lower levels of education, even though both groups displayed similar amyloid beta levels.

"Our study was designed to look for trends, not prove cause and effect, but the major implication of our study is that exposure to education and better cognitive performance when you're younger can help preserve cognitive function for a while even if it's unlikely to change the course of the disease," says Rebecca Gottesman, corresponding author on the new study.

The distinction is particularly important for researchers trialing experimental treatments and evaluating the efficacy of potential new drugs. It suggests cognitive tests may not be a useful way to objectively evaluate how effective a new treatment may be, as individuals with similar levels of Alzheimer's pathology could demonstrate different cognitive scores depending on education levels.

"Our data suggest that more education seems to play a role as a form of cognitive reserve that helps people do better at baseline, but it doesn't affect one's actual level of decline," explains Gottesman. "This makes studies tricky because someone who has good education may be less likely to show a benefit of an experimental treatment because they are already doing well."

Gottesman suggests to overcome this problem in future studies cognitive performance must be evaluated in individuals over time instead of measured at a single point. This would hopefully account for the variations in individual cognitive responses to prospective treatments. The research also suggests while higher levels of eduction may keep one's brain cognitively functional, at least temporarily, it doesn't fundamentally alter the pathological course of the disease.

The new study was published in the Journal of Alzheimer's Disease.