The goal of the Cognitive and Emotional Health Project: The Healthy Brain is to assess the state of epidemiologic research on demographic, social and biologic determinants of cognitive and emotional health in aging populations, and the pathways by which cognitive and emotional health may reciprocally influence each other. As a first step, a comprehensive review of measures that have been (or could be) used in epidemiologic research was undertaken. Measures in four domains are reviewed: (1) cognitive health, (2) emotional health, (3) demographic/social factors, and (4) biomedical/physiologic factors.
(1) Cognitive health. Significant changes in cognitive function develop with age. These changes are evident in several major aspects of mental ability. However, declines do not develop uniformly, either within or across cognitive domains. The nature of the change that occurs, the point at which changes become apparent, and the magnitude and rate of change vary, depending upon the cognitive function in question. This section reviews available measures of five major areas of cognitive ability, ranked by their sensitivity to variation at the high end of the cognitive spectrum: (a) learning & memory, (b) executive function abilities (e.g. concept formation and abstract thought), (c) language, (d) visuospatial abilities, and (e) sustained attention (the ability to focus and perform a simple task). Highlighted are cognitive tasks that have been employed in epidemiologic studies, with citations to the major studies in which they have been used. This section also provides an overview of the major epidemiologic studies that have examined cognitive change, and some of the predictors of change that have been identified, such as education, physical activity, mood, and a variety of medical conditions.
(2) Emotional health. An emerging body of epidemiologic data links a variety of health outcomes (most notably mortality and cardiovascular disease) to emotions. While there is clearly a reciprocal relationship between health and emotions, this review focuses on the role of emotions in the etiology of disease, rather than as a consequence of disease or as part of the process of disease management. This section reviews available measures of various emotional constructs and highlights data showing that some of these constructs are predictive of cognitive health. For example, self-efficacy, defined as an individual's sense of competence or ability (in general or in particular areas), emerged as one of only four direct predictors of cognitive change in a 2.5-year follow-up study of older community-dwelling residents. Depression has also been linked to cognitive decline among the community-dwelling elderly. Other emotional constructs, such as hostility or psychological stress, may be deleterious to cognitive health, but epidemiologic evidence is lacking.
(3) Demographic and social factors. Demographic and social measures have long been used by epidemiologists to predict health outcomes. Socioeconomic status, which can be measured in multiple ways (e.g. education, income, occupation, wealth, material deprivation, subjective social status, income inequality), is one of the most robust predictors of health, as is social integration, defined as the degree to which an individual is integrated into, connected to, or embedded in society. Religion and spirituality, immigration and acculturation, racism and other types of discrimination, and exposure to violence are receiving increasing attention as factors that may influence health. This section reviews available demographic and social measures and provides detailed discussion of epidemiologic findings on the link between some of these measures and mortality, physical and cognitive health. The demographic and social domains are ordered roughly by of the amount of existing epidemiologic evidence connecting these factors to health.
(4) Biomedical and physiologic factors. This section lists existing biomedical and physiologic measures that have been used as predictors of cognitive or emotional health in large-scale epidemiologic studies. It then provides annotated references for studies that have used and/or discussed these measures. The domains covered include: cardiovascular system, hypothalamic pituitary adrenal axis, use of nonsteroidal anti-inflammatory agents, antioxidants, metabolic system, cholesterol, lung function, physical activity, brain structure, genetics, sympathetic nervous system, immune function, estrogen, and renal function. These domains/measures are also likely to be in the pathway(s) connecting emotional and cognitive health. For example, there are at least three processes by which emotional health could influence cognitive health: (a) emotions influence sympathetic and hypothalamic-pituitary-adrenal axis processes that could directly influence cognitive health; (b) these factors influence cardiovascular health which in turn might affect cognitive health; (c) these factors influence behaviors (e.g. physical activity) that might influence cognitive health.