Alzheimer's Disease Prevention

by National Institute on Aging

These days, it seems that newspapers, magazines, and TV are full of stories about ways to stay healthy, eat right, and keep fit. Lots of people are concerned about staying healthy as they get older. They wonder whether they can do anything to prevent diseases that happen more often with age, such as Alzheimer's disease (AD). AD has no known cure, and the secrets to preventing it are not yet known. But research supported by the National Institute on Aging (NIA) and other public and private agencies offers tantalizing clues about the origins and development of AD. These findings are raising hopes that someday it might be possible to delay the onset of AD, slow its progress, or even prevent it altogether. Delaying by even 5 years the time when AD symptoms begin could greatly reduce the number of people who have the disease.

The National Institute on Aging, part of the Federal Government's National Institutes of Health, has primary responsibility for research on AD and age-related decline in cognitive abilities (such as thinking, decision-making, and language skills). This responsibility is part of a larger mission to understand the nature of aging and find ways to help people stay physically, emotionally, and cognitively healthy for as long as possible.

Several years ago, NIA, the National Institute of Mental Health, and the National Institute of Neurological Disorders and Stroke launched The Cognitive and Emotional Health Project, which has begun to identify and describe the diverse lifestyle factors that possibly affect the emotional health and cognitive abilities of older adults. Further research on the most promising factors will be necessary to determine whether any will result in strategies that can help people remain mentally and emotionally vibrant as they age. The hope is that successful strategies will also contribute to our knowledge of what goes wrong in the brain during the development of neurodegenerative diseases like AD.

Preventing a Complex Disease Like AD is a Challenge

Many diseases, such as diabetes, heart disease, and arthritis, are complex. They develop when genetic, environmental, and lifestyle factors work together to cause a disease process to start and then progress. The importance of these factors may differ for each person. AD is one of these complex diseases. It develops over many years, and it appears to be affected by a number of factors that may increase or decrease a person's risk of developing the disease. We don't have control over some of the risk factors for AD. We can do something about other possible AD risk factors, though. The effect on any particular person of risk factor changes will likely depend on his or her genetic makeup, environment, and lifestyle

AD Risk Factors We Can't Control

Age is the most important known risk factor for AD. The risk of developing the disease doubles every 5 years over age 65. Several studies estimate that up to half the people older than 85 have AD. These facts are significant because of the growing number of people 65 and older. More than 34 million Americans are now 65 or older. Even more significant, the group with the highest risk of AD - those older than 85 - is the fastest growing population group in the country.

Genetics is the other known AD risk factor that a person can't control. Scientists have found genetic links to the two forms of AD. Early-onset AD is a very rare form of the disease that can occur in people between the ages of 30 and 65. In the 1980s and early 1990s, researchers found that mutations (or changes) in certain genes on three chromosomes cause early-onset AD. If a parent has any of these genetic mutations, his or her child has a 50-50 chance of inheriting the mutant gene and developing early-onset AD.

Late-onset AD, the more common form, develops after age 65. In 1992, researchers found that certain forms of the apolipoprotein E (APOE) gene can influence AD risk:

• APOE ε2, a rarely occurring form, may provide some protection;
• APOE ε3, the most common form, plays a neutral role; and
• APOE ε4, which is found in about 40 percent of people with AD; APOE ε4 lowers the age of onset and thus increases risk. (Having this gene form does not mean that a person will definitely develop AD; it only increases risk. Many people who develop AD do not have the APOE ε4 form.)

Researchers are now intensively searching for other risk factor genes that may be linked to late-onset AD. Discovering these genes is essential for understanding the very early biological steps leading to AD and for pinpointing targets for drug development and other prevention or treatment strategies. It's also critical for developing better ways to identify people at risk and determining how AD risk factor genes may interact with other genes or with lifestyle or environmental factors to affect AD risk in any one individual.

In 2003, the NIA announced a major expansion of AD genetics research efforts. The AD Genetics Study is collecting genetic material from individuals in families with two or more living brothers or sisters who have late-onset AD. This valuable resource will allow geneticists to speed up the discovery of additional AD risk factor genes.

The Search for AD Prevention Strategies

Though we can't do much about our age or genetic profile, recent research suggests that maintaining good overall health habits may help lower the chances of developing several serious diseases, including ones affecting the brain. This booklet describes a number of health, lifestyle, and environmental factors that could make a difference in AD and that are being actively studied by scientists.

Many of these potential factors have been identified in observational and animal studies. At present, they are only associated with changes in AD risk. Only further research, including clinical trials, will reveal whether, in fact, these factors can help to prevent AD. It is important to understand that the degree to which a person might be helped by any of these factors may be very slight, especially if the person has inherited a bad form of a risk factor gene. That is why it is so important to also focus on other parts of the AD prevention research mission. At the same time that scientists are examining lifestyle factors, many others are developing drugs that can enhance protective biochemical pathways or block pathways that lead to cognitive decline and AD.

About the Author

www.nia.nih.gov
NIA, one of the 27 Institutes and Centers of NIH, leads a broad scientific effort to understand the nature of aging and to extend the healthy, active years of life. In 1974, Congress granted authority to form NIA to provide leadership in aging research, training, health information dissemination, and other programs relevant to aging and older people.