Reaching age 40 may be a milestone for the mind as well as the body, according to a new study. Researchers have isolated a set of genes in the human brain that don’t quite work as well after age 40 as they used to and may help explain the natural mental decline that occurs with age. In the study, published in the journal Nature, researchers looked at the functioning of genes in brain samples from deceased individuals ranging in age from 26 to 106 and identified a set of genes that are not as active in people over age 40.
