The association of total cholesterol with processing speed is moderated by age in mid- to late-age healthy adults

Objectives: To investigate the nature of the association of normal levels of total cholesterol with cognitive function and the contribution of age to this association. Methods: A sample of 61 senior executives, who were summoned for an annual medical examination with approximately four measurements of total cholesterol during 4 years, were examined with a computerized cognitive battery assessing mental processing speed as a sensitive measure of cognitive decline. We examined the association of total cholesterol with processing speed and the moderating effect of age on this association. Results: A multiple regression analysis yielded a significant interaction between cholesterol and age for processing speed (p =.045). In order to examine the source of the interaction, simple slope analysis was performed. A significant negative high correlation was found for young subjects (p =.021), while no significant correlation was observed at middle (p =.286) or older (p =.584) age. The difference in slopes was robust to adjustment for potential confounding factors, including body mass index, and fasting glucose. Conclusions: Within the normal range, higher total cholesterol levels were associated with better processing speed in younger ages and this association diminished with increasing age. Our findings highlight the important role of brain cholesterol in good cognitive functioning.