Alzheimer’s disease is an age-related and irreversible brain disorder that develops over a period of years. Initially, people experience memory loss and confusion. These symptoms gradually lead to behavior and personality changes, a decline in other cognitive abilities (such as thinking, decision-making, and language skills), and ultimately to a severe loss of mental function. These losses are related to the breakdown of the connections between certain nerve cells in the brain and the eventual death of many of these cells. AD is one of a group of disorders, termed dementias, that are characterized by cognitive and behavioral problems.
The course of this disease varies from person to person, as does the rate of decline. In most people with AD, symptoms first appear after age 65. Although the risk of developing AD increases with age, AD and dementia symptoms are not part of normal aging. AD and other dementing disorders are caused by diseases that affect the brain.
The Impact of AD
AD is the most common cause of dementia among people age 65 and older. It presents a major health problem for the United States because of its enormous impact on individuals, families, the health care system, and society as a whole. Scientists estimate that 4.5 million people currently have the disease, and the prevalence (the number of people with the disease at any one time) doubles for every 5-year age group beyond age 65.
These numbers are significant now and will become even more so in the future because of dramatic increases in life expectancy since the turn of the century. Researchers estimate that by 2050, 13.2 million Americans will have AD if current population trends continue and no preventive treatments become available (Hebert et al., 2003). Approximately 4 million Americans are age 85 years or older, and this age group is one of the fastest growing segments of the population. It is also the group with the highest risk of AD. The U.S. Census Bureau estimates that nearly 19 million Americans will be age 85 and older by the year 2050. Some experts who study population trends suggest that the number could be even greater. This trend is not only apparent in the U.S. but also worldwide. As more and more people live longer, the number of people affected by diseases of aging, including AD, will continue to grow. For example, one study showed that nearly half of all people age 85 and older have some form of dementia (Evans et al., 1989).
These prevalence trends translate into a huge impact on people with the disease, their families and friends, and caregivers. Slightly more than half of AD patients receive care at home, while the remainder are cared for in a variety of health care institutions. During their years of AD caregiving, spouses, relatives, and friends experience emotional, physical, and financial stress.
They watch their loved ones become more and more forgetful, frustrated, and confused. Eventually, the person with AD does not even recognize his or her nearest and dearest relatives and friends. Caregivers—most of whom are women—must juggle child care, jobs, and other responsibilities along with caring for relatives with AD who cannot function on their own. As the disease runs its course and the abilities of people with AD steadily decline, family members face difficult decisions about the long-term care of their loved ones. Frequently, they turn to assisted living facilities, then nursing homes, for care and support. The number of caregivers—and their needs—can be expected to escalate rapidly as the population ages and as the number of people with AD grows.
The increasing number of people with AD and the costs associated with the disease mean that AD puts a heavy economic burden on society. The annual national direct and indirect costs of caring for AD patients have been estimated to be as much as $100 billion (Ernst and Hay, 1994; Ernst et al., 1997; Huang et al., 1988).
AD: An Urgent National Research Priority
Given our aging population, the magnitude of AD as a national health problem is steadily increasing. This makes the disease an urgent research priority. Interventions that could delay the onset of AD would have an enormous positive public health impact because they would greatly reduce the number of people with the disease. This in turn would reduce the personal and financial costs associated with caring for them.
AD research supported by the Federal Government is divided into three broad, overlapping areas: causes/risk factors, diagnosis, and treatment/caregiving. Research into the basic biology of the aging nervous system is critical to understanding what goes wrong in the brain of a person with AD. Understanding how nerve cells lose their ability to function and communicate with each other and the reasons why some nerve cells die and others do not is a central part of scientific efforts to discover what causes AD. Assessing factors that may increase or decrease risk of devel-oping AD is a growing component of this research effort.
Many researchers are also looking for better ways to diagnose AD in the early stages and to identify the earliest brain changes that could indicate that the AD process has begun. Investigators are striving to identify markers of early dementia, improve ways to test patient function, improve neuroimaging technologies, and enhance case-finding and sampling methods for population studies.
Other researchers are working to discover and develop interventions that may help treat symptoms, slow the progress of AD, delay its onset, or even prevent the disease. Many of these interventions are now being tested in clinical trials. Finally, scientists and many health care professionals are seeking better ways to help people with AD and their caregivers cope with the decline in mental and physical abilities and the problem behaviors that accompany the disease.
An important complement to the National Institutes of Health’s (NIH) research initiatives in AD are its efforts to educate and inform people with AD, their families, the public, providers, and others interested in the disease. The National Institute on Aging (NIA) Alzheimer’sDisease Education and Referral (ADEAR) Center (www.alzheimers.nia.nih.gov) provides a variety of materials on AD, including information about caregiving, diagnosis and treatment, and results of research findings.For example, NIA’s booklet for the general public, Alzheimer’s Disease: Unraveling the Mystery, uses illustrations and text to explain AD, highlight ongoing research, and describe efforts to support caregivers of people with AD. Another booklet for lay audiences, Genes, Lifestyles, and Crossword Puzzles: Can Alzheimer’s Disease be Prevented?, summarizes the latest research findings on AD risk factors and potential prevention strategies. The ADEAR Center also maintains a database of AD clinical trials, develops recommended reading lists, and provides referrals to local AD resources. In addition, all of the NIA-supported Alzheimer’s Disease Centers (ADCs) have education and information programs that work locally to disseminate information about AD.
We now know a lot about AD — what it is, who can get it, how it develops, and what course it follows. We also have made significant progress in the critical area of early diagnosis and have some promising leads on possible treatments. All of the research has deepened our understanding of this devastating disease. It also has expanded our knowledge about other late-life neurodegenerative diseases, brain function in healthy older people, and ways in which to minimize normal age-related cognitive decline.
The 2004-2005 Progress Report on Alzheimer’s Disease describes this important research effort. It begins with a description of our current knowledge about AD. This provides the foundation for the next section, which highlights recent studies supported by NIA and other NIH Institutes. The report closes with a section called “Outlook for the Future,” which takes a look at some exciting AD research initiatives. These initiatives are designed to accelerate laboratory and clinical research and collaboration across the Federal Government and in association with the private sector so that research findings can be translated expeditiously into real advances for patients, families, and caregivers.
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