Cognitive reserve moderates decline in information processing speed in multiple sclerosis patients

Abstract

Cognitive reserve is widely recognized as a moderator of cognitive decline in patients with senile dementias such as Alzheimer's disease. The same effect may occur in multiple sclerosis (MS), an immunologic disorder affecting the central nervous system. While MS is traditionally considered an inflammatory, white matter disease, degeneration of gray matter is increasingly recognized as the primary contributor to progressive cognitive decline. Our aim was to determine if individual differences in estimated cognitive reserve protect against the progression of cognitive dysfunction in MS. Ninety-one patients assessed twice roughly 5 years apart were identified retrospectively. Cognitive testing emphasized mental processing speed. Cognitive reserve was estimated by years of education and by performance on the North American Adult Reading Test (NAART). After controlling for baseline characteristics, both years of education (p = .013) and NAART scores (p = .049) significantly improved regression models predicting cognitive decline. Symbol Digit Modalities Test (SDMT) performance showed no significant change in patients with > 14 years of education, whereas it declined significantly in patients with ≤ 14 years of education. We conclude that greater cognitive reserve as indexed by either higher premorbid intelligence or more years of education protects against the progression of cognitive dysfunction in MS.