In a follow-up study of 399 AD cases and controls, elevated serum BDNF was found to be specifically related to poorer memory performance among AD cases [14] whereas Komulainen and colleagues [15] found that lower plasma BDNF levels were significantly related to poorer scores on tests of language and memory among women in a population based sample of aging men and women (n = 1389). This evidence concerns the gene BDNF and Alzheimer disease.