Effects of demographic factors on cortical thickness in Alzheimer's disease.

The aim of this study was to investigate the effect of demographic factors (age of onset, sex and years of education) on the distribution of cortical thickness in a large sample of patients with Alzheimer's disease (AD). The study participants consisted of 193 AD patients and 142 controls with no cognitive impairment (NCI) that were measured with cortical thickness across the entire brain. The effects of demographic factors on cortical thickness were analyzed by applying linear regression after controlling confounding factors. Older individuals in NCI group showed more cortical thinning in frontal, temporal association cortices and insula than younger participants. Early onset AD was associated with cortical thinning in the parietal lobe, whereas late onset AD was associated with cortical thinning in the medial temporal region. The NCI group demonstrated sex-related differences in cortical thickness, although those differences were not present in the AD group. While the education effect was absent in NCI individuals, high levels of education in the AD group correlated with cortical thinning in the frontal and temporoparietal association cortices. Our results show that AD with earlier onset and higher education had suffered more pronounced cortical atrophy in specific parts of the brain than their counterparts, which may be related to cognitive reserve theory.