Cognitive Aging

 The number of Americans over the age of 65 is projected to more than double in the next forty years, increasing from 40.2 million in 2010 to 88.5 million in 2050.1 It will become increasingly important to understand the cognitive changes that accompany aging, both normal and pathologic. Although dementia and mild cognitive impairment are both common, even those who do not experience these conditions may experience subtle cognitive changes associated with aging. These normal cognitive changes are important to understand because, first, they can affect an older adult’s day to day function and, second, they can help us distinguish normal from disease states. In this paper, we first describe the neurocognitive changes observed in normal aging. This is followed by a description of the structural and functional alterations seen in aging brains that may explain observed cognitive changes. We will then discuss some of the practical implications of normal cognitive aging. We will conclude with a discussion of what is known about factors that may mitigate age-associated cognitive decline.   Before discussing normal age-related changes, it is necessary to mention a few common methodological challenges that plague the study of normal brain aging. As with all studies of aging, selection bias is a challenge- many potential study participants decline enrollment because they are either too healthy (and busy) or too ill. Additionally, people with limited social or financial support and functional limitations may be less likely to enroll in studies. This results in study findings that may not be generalizable to all older adults.