Defining Optimal Brain Health in Adults: A Presidential Advisory From the American Heart Association/American Stroke Association

Abstract

Cognitive function is an important component of aging and predicts quality of life, functional independence, and risk of institutionalization. Advances in our understanding of the role of cardiovascular risks have shown them to be closely associated with cognitive impairment and dementia. Because many cardiovascular risks are modifiable, it may be possible to maintain brain health and to prevent dementia in later life. The purpose of this American Heart Association (AHA)/American Stroke Association presidential advisory is to provide an initial definition of optimal brain health in adults and guidance on how to maintain brain health. We identify metrics to define optimal brain health in adults based on inclusion of factors that could be measured, monitored, and modified. From these practical considerations, we identified 7 metrics to define optimal brain health in adults that originated from AHA's Life's Simple 7: 4 ideal health behaviors (nonsmoking, physical activity at goal levels, healthy diet consistent with current guideline levels, and body mass index <25 kg/m²) and 3 ideal health factors (untreated blood pressure <120/<80 mm Hg, untreated total cholesterol <200 mg/dL, and fasting blood glucose <100 mg/dL). In addition, in relation to maintenance of cognitive health, we recommend following previously published guidance from the AHA/American Stroke Association, Institute of Medicine, and Alzheimer's Association that incorporates control of cardiovascular risks and suggest social engagement and other related strategies. We define optimal brain health but recognize that the truly ideal circumstance may be uncommon because there is a continuum of brain health as demonstrated by AHA's Life's Simple 7. Therefore, there is opportunity to improve brain health through primordial prevention and other interventions. Furthermore, although cardiovascular risks align well with brain health, we acknowledge that other factors differing from those related to cardiovascular health may drive cognitive health. Defining optimal brain health in adults and its maintenance is consistent with the AHA's Strategic Impact Goal to improve cardiovascular health of all Americans by 20% and to reduce deaths resulting from cardiovascular disease and stroke by 20% by the year 2020. This work in defining optimal brain health in adults serves to provide the AHA/American Stroke Association with a foundation for a new strategic direction going forward in cardiovascular health promotion and disease prevention.

Keywords: AHA Scientific Statements; aging; brain; cognitive dysfunction; prevention and control; risk factors; stroke.

Figure 1

Major determinants of optimal brain health. Genetic, environmental, and behavioral factors can either promote or hinder optimal brain health. Vascular risk factors negatively influence optimal brain health through cardiovascular and cerebrovascular alterations that produce brain dysfunction and damage, leading to cognitive dysfunction.

Figure 2

The neurovascular unit (NVU): the guardian of the homeostasis of the brain microenvironment. Schematic representation of the NVU at the level of the cerebral microvasculature (arterioles, capillaries). The NVU is constituted by endothelial cells, smooth muscle cells (replaced by pericytes in capillaries), astrocytes, neurons, perivascular cells, and the extracellular matrix, a complex meshwork of proteins and carbohydrates that provides support to the different cellular constituents. The NVU is responsible for maintaining the homeostasis of the cerebral microenvironment, ensuring an optimal milieu for the function of neurons and other brain cells. The NVU regulates the delivery of blood flow to the brain, ensuring that it is well matched to its energetic needs; is the site of the blood-brain barrier (BBB), which controls the bidirectional trafficking of molecules into and out of the brain; is involved in the trafficking of immune cells, promoting immunosurveillance in the normal state and innate and adaptive immune responses after brain injury; produces neuronal, glial, and vascular growth factors that support the reciprocal survival of its cellular constituents and the adjacent brain parenchyma; and is a major conduit for the clearance of potentially deleterious byproducts of brain activity such as β-amyloid and tau through transvascular, perivascular, and paravascular (glymphatic) pathways. CBF indicates cerebral blood flow.