Cognitive reserve, one of the determinants of the progression of Alzheimer's disease

Objective. To appraise the validity of the Yaakov Stern's theory, which postulates that the first cognitive deficits of Alzheimer's disease are delayed in patients with high cognitive reserve, compared to those with low cognitive reserve, but is subsequently associated with faster cognitive decline when cerebral lesions have reached some degree of severity. Methods. A retrospective study of 318 patients with Alzheimer's disease without associated cerebral disorders, was performed in the Memory Clinic of the University Hospital of Strasbourg. The patients were divided into 5 groups according to the degree of cognitive reserve assessed by the level of education (primary, middle school, intermediary, high school and higher education). Cognitive status was assessed by the scores on the Mini Mental Status at the first examination and during a 4-year or more follow-up. Slopes of cognitive decline were computed and compared between groups by beta linear regression. Results. Patients in the higher education group had higher MMSE scores than those in the other groups at the first consultation, but a statistically significant steeper slope during the follow-up. Conclusion. Our results are congruent with the Stern's theoretical model, assuming that high cognitive reserve brings into play compensation mechanisms which hinder the onset of clinical cognitive decline in patients with Alzheimer's disease, but then is associated with a faster decline at a later stage when the reserve is exhausted.