Education delays accelerated decline on a memory test in persons who develop dementia

OBJECTIVE: To test the cognitive reserve hypothesis by examining the effect of education on memory decline during the preclinical course of dementia. BACKGROUND: Low education is a well known risk factor for Alzheimer disease (AD). Persons destined to develop AD experience an accelerated rate of decline in cognitive ability, particularly in memory. The cognitive reserve hypothesis predicts that persons with greater education begin to experience acceleration in cognitive decline closer to the time of diagnosis than persons with lower reserve, but that their rate of decline is more rapid after the time of acceleration due to increased disease burden. METHODS: We studied the influence of education on rates of memory decline as measured by the Buschke Selective Reminding Test in 117 participants with incident dementia in the Bronx Aging Study. Subjects had detailed cognitive assessments at entry and at annual follow-up visits. We estimated the time at which the rate of decline begins to accelerate (the change point), and the pre- and post-acceleration rates of decline, from the longitudinal data using a change point model. RESULTS: Each additional year of formal education delayed the time of accelerated decline on the Buschke Selective Reminding Test by 0.21 years. Post-acceleration, the rate of memory decline was increased by 0.10 points per year for each year of additional formal education. CONCLUSIONS: As predicted by the cognitive reserve hypothesis, higher education delays the onset of accelerated cognitive decline; once it begins it is more rapid in persons with more education.