Defining Cognitive Reserve and Implications for Cognitive Aging

Abstract

Purpose of review: The aim of this review is to summarize current conceptual models of cognitive reserve (CR) and related concepts and to discuss evidence for these concepts within the context of aging and Alzheimer's disease.

Recent findings: Evidence to date supports the notion that higher levels of CR, as measured by proxy variables reflective of lifetime experiences, are associated with better cognitive performance, and with a reduced risk of incident mild cognitive impairment/dementia. However, the impact of CR on longitudinal cognitive trajectories is unclear and may be influenced by a number of factors. Although there is promising evidence that some proxy measures of CR may influence structural brain measures, more research is needed. The protective effects of CR may provide an important mechanism for preserving cognitive function and cognitive well-being with age, in part because it can be enhanced throughout the lifespan. However, more research on the mechanisms by which CR is protective is needed.

Keywords: Aging; Alzheimer’s disease; Biomarkers; Cognition; Cognitive reserve; Review.

Fig. 1

Hypothetical models illustrating the possible associations between longitudinal cognitive trajectories and pathology as a function of CR (as measured by proxy variables), based on Stern’s Fig. 1 from [19]. Although the cognitive trajectories of the high and low CR participants are the same before and after onset of cognitive decline in (a–c) (as illustrated by black solid lines), the study results may differ, depending what part of the trajectory was observed (as illustrated by dashed blue horizontal lines, showing linear slopes of cognitive trajectories (a–c)). Conceptual model illustrating the lifespan impact of genetics, cognitive reserve, and age- and disease-related pathology on an individual’s risk of cognitive impairment as a function of age (d). Evidence to date suggests that CR proxy measures impact the level of cognition (as shown by the intercept effect in (a–c)), which might delay the onset of cognitive decline (as shown by the later cognitive trajectory change point among individuals with high CR (a–c)). Evidence also suggests that CR impacts risk of cognitive impairment (as shown by points A vs. C (d)). While protective factors (such as high levels of CR) may move the threshold of cognitive impairment to a later age (thereby reducing risk of cognitive impairment; point C (d)), risk factors (such as low levels of CR, age- and disease-related brain changes, and other factors not discussed here (e.g., psychiatric conditions; poor health)) may move the threshold for cognitive impairment to a younger age (point A (d)). Of note, genetics and lifestyle factors are hypothesized to act throughout the lifespan, whereas the impact of age- and disease-related pathology may not impact cognition until middle age or later. (Reprinted from: Stern, Y, Cognitive reserve. Neuropsychologia. 2009; 47:2015–2028; with permission from Elsevier) [19]