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CDC Brain Health Initiative Focuses On Emerging Research on Cognitive VitalityMarch 20, 2006
MEDIA CONTACTS: Anyone who has not yet heeded the public health message to get off the couch needs to know that there is another good reason to listen to the experts. Reducing your cardiovascular risk factors and staying physically active may help preserve your mind as well as your body. And there may be other things you can do to preserve cognitive health. For years people believed that a decline in mental abilities was an inevitable part of aging. That view is now proving to be incorrect. A reexamination of available research has begun to focus public health attention on lifestyle changes to help maintain cognitive performance. Although much more research is needed in this area, the good news is that many of these approaches -- controlling weight and blood pressure, staying physically active, and being involved in the community -- are the same behaviors that many people have already adopted for their physical and emotional health. "All the things that we know are bad for your heart turn out to be bad for your brain," said Marilyn S. Albert, Ph.D., director of the Division of Cognitive Neuroscience at Johns Hopkins University School of Medicine. Recent findings take on even more importance when looking at the projected growth in the older population, which is the group most at risk for cognitive decline. The number of adults aged 65 years and older (35 million in 2000) is expected to double by 2030, based on census estimates. These older adults, who now make up 12 percent of the U.S. population, will comprise almost 20 percent by 2030. Maintaining cognitive health will not only improve the quality of life for many of these older adults, but it also will allow them to continue to participate in society, to contribute to the economy, and to reduce the costs of their care. COGNITIVE HEALTH"If we maintain cognitive function over time, then we are more likely to be functionally independent." -- Dr. Marilyn Albert Because there is no uniform definition of cognitive health, researchers are still struggling to describe all the aspects of cognitive health. Clearly, cognitive health includes the absence of cognitive decline, but the term goes well beyond that to include optimal mental functioning. A 2001 workshop on the healthy brain conducted by the National Institutes of Health concluded that cognition "should not be defined simply as the absence of diseases such as Alzheimer's disease. While the study of cognitive health cannot ignore dementia, the definition of cognitive health should be multidimensional and focus on successful aging instead of normal aging." The concept of successful aging embraces the more positive aspects of aging, whereas "normal aging" is frequently used to describe declines associated with the aging process. A recent literature review by the Cognitive and Emotional Health Project (CEHP), an initiative involving researchers from the National Institutes of Health and several universities, used a global approach to defining cognitive health. "We said cognitive health shouldn't just be the absence of disease, but rather the development and preservation of a multidimensional cognitive structure," said Hugh C. Hendrie, M.B., Ch.B., D.Sc., who chairs the CEHP Critical Analysis Committee. "That structure allows elderly people to maintain social connectedness, an ongoing sense of purpose, and the ability to function independently and to permit functional recovery," explained Hendrie, who is also a psychiatry professor and scientist at the Indiana University Center for Aging Research. The CEHP team expects to publish its review in Alzheimer's & Dementia: The Journal of the Alzheimer's Association in the spring of 2006. Cognitive function "has to do with memory, basic cognitive skills, and trying to extend the length of time that people function normally," said Steve McConnell, senior vice president of public policy at the Alzheimer's Association. Dr. Albert added that, "Even if we have physical disabilities, we can use our mental faculties to figure out how to get around them, how to get the help we need, how to organize our environment so that we are maximally independent." The components of cognitive health that most experts agree on include language, thought, memory, executive function (the ability to plan and carry out tasks), judgment, attention, perception, remembered skills such as driving, and the ability to live a purposeful life (National Research Council, 2000, The Aging Mind). Good cognition is essential to a person's sense of being human. It involves having a good quality of life; feeling positive about one's self; staying connected with others; being able to adapt to life; maintaining skills in task- specific, decision-making, and computational areas; and maintaining independent living. Some researchers believe that certain aspects of cognition actually improve with aging, such as wisdom and the ability to exercise good judgment on important life decisions (Baltes, 1990). "So if a young woman is considering marrying, she probably would get better advice from her grandparents than anyone else," Dr. Hendrie said. In The Aging Mind, the National Research Council described wisdom as "the coordinated use in making life choices of factual and procedural knowledge about life; knowledge about life conflicts, contexts, and priorities; and knowledge about recognizing and managing uncertainty." COGNITIVE DECLINE Cognitive impairment involves problems with memory, understanding or using words, and identifying objects. Declining cognition leads to a loss of sense of self and of lifelong memories; a decreased ability to cope with the normal demands of living; problems accessing health care systems; greater vulnerability to disease, injury, malnutrition, crime, and possibly elder abuse; and eventually a loss of independence. That loss of independence often becomes a burden on families and society, as the individual requires more intensive care and often institutionalization. Cognitive decline can range from the normal changes associated with the aging brain, to mild cognitive impairment, to dementia. These are different conditions, not necessarily a progression of one disease. Many people never develop any serious decline in their cognitive performance, and those who develop mild cognitive problems do not necessarily develop dementia. Normal Changes. Many people retain their cognitive capabilities into very old age. Some age-related cognitive decline -- slower information processing and mild memory impairment -- does occur. This normal decline is attributed to a decrease in brain size and changes in the way that neurons (nerve cells) function. This is not considered dementia and does not interfere with a person's ability to perform activities of daily living or to maintain social connections. Many people adapt or develop ways to compensate for these slight losses, thus maintaining their ability to function reasonably well in their daily routines and social lives. Most studies suggest that "there is some cognitive decline that occurs in the elderly, but it is specific to particular parts of the cognitive process," Dr. Hendrie said. "Some parts of cognition, such as language, are left quite intact, while other parts, such as the ability to recall a list of words, decline a little bit, even in healthy elderly," he said. "In some areas of cognitive function there is no difference at all between the old and young." Mild Cognitive Impairment. Some people develop further cognitive and memory problems -- called mild cognitive impairment or MCI -- as neurons die. Those with MCI have more memory impairment for their age than their peers, yet certain skills -- such as language, reasoning, problem solving, driving -- may still be essentially intact. MCI does not interfere with their ability to perform daily activities. Cognitive impairment may involve things like difficulties balancing a checkbook, organizing activities, or making decisions. According to Dr. Hendrie, sequential neuropsychological testing can help to determine that a person has MCI. Testing will show decline over time. Having mild cognitive impairment does not mean dementia. Finding ways to prevent people with MCI from developing dementia is a key goal of researchers and public health experts. While not all people with MCI also develop dementia, those with this condition do have a higher risk for dementia compared to other adults. One study found that approximately 40 percent of people over age 65 who were diagnosed with mild cognitive impairment developed dementia within three years. MCI is three to four times as common as Alzheimer's disease, Dr. Hendrie noted. Dementia. Dementia results in much more significant disability and a lower quality of life than MCI. It is not until many nerve cells die that a person develops dementia. Dementia is not a single disease, but rather a collective term for numerous brain disorders that affect intellectual and social function and interfere with activities of daily living. A diagnosis of dementia generally centers on the loss of two or more brain functions, such as memory, language, perception, reasoning, or judgment. Advanced forms of dementia may include the inability to control emotions, agitation, delusions, and hallucinations. Dementias such as Alzheimer's disease (AD) and Lewy body dementia are accompanied by abnormal changes in the microscopic structure of the brain. AD, the most prevalent form of dementia, is characterized by two abnormalities in the brain -- amyloid (protein fragment) plaques in brain tissue between nerve cells and neurofibrillary tangles found within neurons. Researchers are still struggling to understand why these develop, whether they are the cause or the result of the disease, and how to prevent dementia. AD comprises 70 percent to 75 percent of all dementias. Vascular dementia, which accounts for 20 percent of all dementias, is caused by brain damage such as stroke arising from cerebrovascular or cardiovascular diseases that restrict blood flow to areas of the brain. Interestingly, autopsy examinations of older people who were not demented sometimes show brain pathology similar to AD or other dementias. Why the same microscopic brain changes affect some people less than others is not yet understood. Some researchers believe there is a "cognitive reserve" related to higher education, literacy, or involvement in social and leisure activities. This reserve appears to protect people against cognitive decline despite pathologic changes associated with dementia (Scarmeas, 2004). However, it is also possible that education levels are tied to the fact that mental stimulation is likely to be higher among people with more education, Dr. Albert of Johns Hopkins noted. Therefore, staying mentally active throughout life may be a more important factor than being well educated. Research by the National Institute on Aging indicated that there are more than 10 reversible conditions that cause or mimic cognitive impairment. These conditions are related to emotional distress, physical illness, medications, nutrition deficiencies, social and cultural restraints, or alcohol abuse. Some of these conditions can be treated. Reversible causes of dementia include an accumulation of cerebrospinal fluid in the brain (normal-pressure hydrocephalus), thyroid dysfunction, and certain vitamin deficiencies. Depression in older people can mimic cognitive decline. "Thus it is important to screen people with early dementia for such treatable causes," said David Thurman, M.D., M.P.H., with the Centers for Disease Control and Prevention's Health Care and Aging Studies Branch, Division of Adult and Community Health, National Center for Chronic Disease Prevention and Health Promotion. Prevalence of Dementia. "Among all seniors 65 years and older, the prevalence of dementia is roughly seven to eight per 100, while the incidence [new cases] is roughly three to four per 100 per year," Thurman said. Those numbers are based on 17 studies of dementia in seniors, all published since 1990. "The incidence is much higher as age increases," he added. The Alzheimer's Association estimates there are 4.5 million people with Alzheimer's disease. It predicts that number will reach 12 million to 16 million by 2050, based on census population projections. Costs of Dementia Care. Not only does dementia create difficulties for families and friends of the person with dementia, but it also increases the cost of care. One study found that annual health care costs were more than $4,000 higher for older patients with dementia than for their unaffected peers. About 75 percent of the higher cost was due to hospitalization and skilled nursing facility care (Hill, 2002). In a 2004 report prepared by the Lewin Group for the Alzheimer's Association, analysis of Medicare claims data showed that beneficiaries with dementia cost Medicare three times more than other older beneficiaries (Saving Lives. Saving Money: Dividends for Americans Investing in Alzheimer Research). Currently, people with Alzheimer's account for 34 percent of Medicare spending even though they constitute less than 13 percent of the population aged 65 and older, according to the association. The annual cost of Alzheimer's disease for businesses is estimated at $61 billion, the Alzheimer's Association reports (Alzheimer's Disease: The Costs to U.S. Businesses in 2002). The costs include $36.5 billion in lost productivity due to employee caregiving and $24.6 billion as the business share of health and long-term care expenditures for people with Alzheimer's disease. These data make it clear that delaying or preventing the onset of disease could save money and relieve human suffering. "The holy grail would be something to interrupt the course of the disease," according to the association's McConnell. "Delaying onset and slowing progression of Alzheimer's would save billions of dollars for America's health programs." MAINTAINING COGNITIVE HEALTH: WHAT THE SCIENCE SAYS Many scientists agree that cerebrovascular disease (and frequently associated conditions such as diabetes, high blood pressure, and the metabolic syndrome, which is a group of risk factors that include abdominal obesity and insulin resistance) and physical activity appear to be most clearly linked to cognitive function. "There is growing evidence that high blood pressure and diabetes are important factors that appear to increase the risk of later developing dementing disease. In addition, it appears that other related factors like inactivity (both physical and social), high cholesterol, and perhaps smoking may contribute to this risk as well," Dr. Thurman explained. Researchers also give credence to the importance of socialization and staying involved in the community, although more research is needed in that area. "There is a great deal of evidence suggesting that physical activity and social engagement play a big role, along with diet as it relates to cardiovascular risk," said James N. Laditka, D.A., Ph.D., M.P.A., director of research at the University of South Carolina Office for the Study of Aging. Those are the key elements of a draft of the Cognitive and Emotional Health Project review that was presented at the June 2005 International Conference on Prevention of Dementia, sponsored by the Alzheimer's Association, Dr. Laditka said. There is also a "lot of evidence that risk factors that are involved in heart disease seem also to be the risk factors for cognitive decline," Dr. Hendrie of Indiana University said. "So hypertension increases the probability of cognitive decline, and treatment of hypertension protects against getting cognitive decline." The same appears to be true for diabetes. Dr. Hendrie suggested that, "Of all the lifestyle factors that were analyzed in our review, perhaps the strongest evidence identified physical activity as a protective factor against cognitive decline." But other scientists say there is not enough data at this point to make a definitive link. The studies reviewed by CEHP also indicate a possible interaction between depression and psychosocial factors in cognitive decline, Dr. Hendrie said. Preventing or mitigating depression and stress through emotional supports or social networks seem to be protective against cognitive decline. Dr. Hendrie cautioned, however, that these associations do not mean that if you adopt all these positive lifestyle factors, you will not ever have cognitive decline. "You could follow a healthy lifestyle and still get cognitive decline." According to Laditka, the strength of the CEHP review -- undertaken at the behest of the National Institute on Aging, National Institute of Mental Health, and National Institute of Neurological Disorders and Stroke -- lies in its focus on studies with the strongest scientific evidence. Dr. Hendrie described the survey and its recommendations as "cautious," looking only at large- cohort (more than 500 subjects) studies conducted over a long period of time. The goal was to "identify common themes that many studies have reported and to indicate where there is a need for more research," said Dr. Albert, who is a member of the CEHP review panel. The CEHP review team found more research in the area of cognitive and emotional health than it expected, Dr. Hendrie added, including a large amount of information on risk factors for cognitive health that has not as yet been published. The CEHP team would like to see methods developed to encourage investigators from these large studies to analyze and publish this information, Dr. Hendrie commented. Beyond consuming a diet that protects the heart, and thus possibly the brain, the link between good nutrition and cognition is so complex that there are no firm conclusions in this area, scientists indicate. "The role of nutrition is unclear in many ways, except for the role of overnutrition that causes obesity. This, of course, contributes to diabetes and hypertension, which are risk factors for dementia," Dr. Thurman pointed out. The epidemiological studies to link diet and cognition would be time-consuming and costly, Dr. Albert added. "So, generally, a lifestyle and diet that promotes heart health is probably the best that we can say about nutrition links," Dr. Laditka said. Scientists also can cite animal studies as plausible explanations for why lifestyle factors might work in humans. Animal models show, for example, that physical activity produces cellular, molecular, and neurochemical changes, and improves blood flow to the brain. Here are some highlights from other recent research:
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