Personality Factors and Social Networks

In addition to the connection with social networks, brain reserve might also be associated with personality factors. Dr. Bennett's studies have suggested that some personality traits, such as how someone reacts to stress, are associated with cognitive function. "Not how much stress you're under, but how you deal with stress, is associated with the loss of episodic memory, which is a hallmark of Alzheimer's disease." Research suggests, for example, that people who worry a lot or have experienced long-term depression or anxiety have twice the risk of cognitive decline.

Loneliness is another factor. It's not just the size of one's social network that is important, but the ease or difficulty one has making social connections. A pattern of unsatisfying relationships correlates with an increased risk of cognitive decline.

Dr. Bennett speculates that a life of stress, depression, and loneliness changes the brain in ways that we don't yet understand. Perhaps such situations create a negative environment in the brain. "This would not directly cause the pathology of Alzheimer's disease, but it may cause some other type of damage that would make Alzheimer's changes more likely to be expressed as memory loss." Dr. Bennett's research also suggests that an extensive social network—not only how many people one knows, but how many people one knows intimately and feels comfortable confiding in—might be protective in its own way. It could be, Bennett says, that "the larger the network, the less likely people are to decline, the less likely they are to experience clinical Alzheimer's disease."

The connections among education, cognitive stimulation, social engagement, and Alzheimer's disease remain unclear. Additional studies will be needed to determine cause-and-effect relationships—to test, for example, whether mental stimulation as an intervention will directly influence the risk of Alzheimer's disease. Without direct evidence, Dr. Hodes explained, "we are not able to conclude with any certainty that pursuing education, keeping your brain active, or developing an extensive social network specifically will prevent Alzheimer's disease." However, he also noted that a body of research—as well as common sense—shows that many of these activities are good for health and aging and their potential benefits for Alzheimer's disease should be active lines of scientific inquiry.

In this vein, cognitive reserve is an important area of AD research. "We know that proper diet and exercise, weight control, lower salt intake, and eating fresh fruits and vegetables can help reduce the likelihood of cardiovascular disease. Similarly, we are trying to determine what people can do in their lives to maintain cognitive health within their genetic constraints," Dr. Bennett told us. "What can we do as young people, as middle-aged people, and even as older people to create brains that would tolerate AD pathology if it developed? As you take your brain into your ninth and tenth decade, it's likely to be assaulted by a variety of insults such as Alzheimer's changes and strokes. You want the most robust, efficient, rapid decision-making, multi-tasking brain you possibly can have, because that may allow you to maintain your cognition, despite all the other things that could happen to it."

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Excerpted from THE ALZHEIMER'S PROJECT: MOMENTUM IN SCIENCE, published by Public Affairs, www.publicaffairsbooks.com.

Alzheimer's Disease (AD)

A progressive degenerative disease of the brain that causes impairment of memory and other cognitive abilities.

Amyloid Precursor Protein (APP)

The larger protein from which beta-amyloid is formed.

ApoE Gene

A gene that codes for a protein that carries cholesterol to and within cells; different forms of the ApoE gene are associated with differing risks for late-onset Alzheimer's disease. This gene may be referred to as a risk factor gene or a "susceptibility gene" because one form of the gene, called APOE4, is associated with the risk of developing late onset AD.

Beta-Amyloid

Derived from the amyloid precursor protein and found in plaques, the insoluble deposits outside neurons. May also be called A-beta.

Beta-Amyloid Plaque

A largely insoluble deposit found in the space between nerve cells in the brain. The plaques in Alzheimer's disease are made of beta-amyloid and other molecules, surrounded by non-nerve cells (glia) and damaged axons and dendrites from nearby neurons.

Cognitive Reserve

The brain's ability to operate effectively even when some damage to cells or brain cell communications has occurred.

Dementia

A broad term referring to a decline in cognitive function that interferes with daily life and activities. Alzheimer's disease is one form of dementia.

Functional MRI (fMRI)

An adaptation of an MRI (see magnetic resonance imaging) technique that measures brain activity during a mental task, such as one involving memory, language, or attention.

Hippocampal Formation

A structure in the brain that plays a major role in learning and memory and is involved in converting short-term to long-term memory. Also called the hippocampus.

Inflammation

The process by which the body responds to cellular injury by attempting to eliminate foreign matter and damaged tissue.

Insulin Resistance

A condition in which the pancreas makes enough insulin, but the cells do not respond properly to it; characterizes and precedes type 2 diabetes.

Magnetic Resonance Imaging (MRI)

A diagnostic and research technique that uses magnetic fields to generate a computer image of internal structures in the body.

Mild Cognitive Impairment (MCI)

A condition in which a person has cognitive problems greater than those expected for his or her age. Amnestic MCI includes memory problems, but not the personality or other cognitive problems that characterize AD.

Neurodegenerative Disease

A disease characterized by a progressive decline in the structure and function of brain tissue. These diseases include AD, Parkinson's disease, frontotemporal lobar degeneration, and dementia with Lewy bodies. They are usually more common in older people.

Oligomers

Clusters of a small number of beta-amyloid peptides.

Oxidative Damage

Damage that can occur to cells when they are exposed to too many free radicals.

Pittsburgh Compound B (PiB)

The radioactive tracer compound used during a PET (see Positron Emission Tomography) scan of the brain to show beta-amyloid deposits.

Pittsburgh Compound B (PiB)

The radioactive tracer compound used during a PET (see Positron Emission Tomography) scan of the brain to show beta-amyloid deposits.

Synapse

The tiny gap between nerve cells across which neurotransmitters and nerve signals pass.

Tau

A protein that helps to maintain the structure of microtubules in normal nerve cells. Abnormal tau is a principal component of the paired helical filaments in neurofibrillary tangles.

Tangles

A protein that helps to maintain the structure of microtubules in normal nerve cells. Abnormal tau is a principal component of the paired helical filaments in neurofibrillary tangles.

Memory

Normal Aging

Genetic Risk Factor

Dominant and Recessive Genes

Genes and Proteins

Protein-Misfolding Disease

Cholesterol

Biomarkers

Disease-Modifying Drug

Transgenic Mice

An animal that has had a gene (such as the human APP gene) inserted into its chromosomes for the purpose of research. Mice carrying a mutated human APP gene often develop plaques in their brains as they age.

Pathology

Microglia

Insulin & Insulin Resistance

Susceptibility Gene

A variant in a cell's DNA that does not cause a disease by itself but may increase the chance that a person will develop a disease.

Susceptibility Genes

A variant in a cell's DNA that does not cause a disease by itself but may increase the chance that a person will develop a disease.

Genome-Wide Association Study

Vascular Disease

Genetics

Genetics

Normal Aging