Alzheimer’s disease (AD) is the seventh leading cause of all deaths in the United States and is virtually tied with the sixth leading cause of death – diabetes. AD is the fifth leading cause of death in Americans aged 65 and older. Although other major causes of death have been on the decrease, deaths because of AD have been rising dramatically. Between 2000 and 2006, heart disease deaths decreased 11.1%, stroke deaths decreased 18.2%, and prostate cancer-related deaths decreased 8.7%, whereas deaths because of AD increased 46.1%.
Older African-Americans and Hispanics are more likely than older white Americans to have AD or other dementia. Current estimates are that African-Americans are about 2 times more likely, and Hispanics about 1.5 times more likely, than their white counterparts to have these conditions. However, the relationship of race and ethnicity to the development of AD and other dementias is complex and not fully understood.
In 2009, nearly 11 million family and other unpaid caregivers provided an estimated 12.5 billion hours of care to persons with AD and other dementias; this care is valued at nearly $144 billion. Medicare payments for services to beneficiaries aged 65 years and older with AD and other dementias are three times higher than for beneficiaries without these conditions. Total payments for 2010 for health care and long-term care services for people aged 65 and older with AD and other dementias are expected to be $172 billion (not including the contributions of unpaid caregivers).
An estimated 5.3 million Americans have AD; approximately 200,000 persons under age 65 with AD comprise the younger-onset AD population. Every 70 seconds, someone in America develops AD; by 2050 the time of every 70 seconds is expected to decrease to every 33 seconds. Over the coming decades, the baby boom population is projected to add 10 million people to these numbers. In 2050, the incidence of AD is expected to approach nearly a million people per year, with a total estimated prevalence of 11-16 million people. Dramatic increases in the numbers of “oldest old” (aged 85 years and older) across all racial and ethnic groups will also significantly affect the numbers of people living with AD.
This report provides information to increase understanding of the public health effect of AD, including incidence and prevalence, mortality, costs of care, and effect on caregivers and society in general. This report also sets the stage for better understanding the relationship between race and ethnicity and the development of AD and other dementias.
AD is the most common cause of dementia. Dementia is characterized by the loss of or decline in memory and other cognitive abilities. It is caused by various diseases and conditions that result in damaged brain cells. To be classified as dementia, the following criteria must be met:
- It must include decline in memory and decline in at least one of the following cognitive abilities:
(1)Ability to generate coherent speech or understand spoken or written language;
(2)Ability to recognize or identify objects, assuming intact sensory function;
(3)Ability to execute motor activities, assuming intact motor abilities, sensory function, and comprehension of the required task; and
(4)Ability to think abstractly, make sound judgments, and plan and carry out complex tasks.
- The decline in cognitive abilities must be severe enough to interfere with daily life.
Different types of dementia have been associated with distinct symptom patterns and distinguishing microscopic brain abnormalities. Increasing evidence from long-term epidemiological observation and autopsy studies suggests that many people have brain abnormalities associated with more than one type of dementia. The symptoms of different types of dementia also overlap and can be further complicated by coexisting medical conditions.
In AD, as in other types of dementia, increasing numbers of nerve cells deteriorate and die. A healthy adult brain has 100 billion nerve cells, or neurons, with long branching extensions connected at 100 trillion points. At these connections, called synapses, information flows in tiny chemical pulses released by one neuron and taken up by the receiving cell. Different strengths and patterns of signals move constantly through the brain’s circuits, creating the cellular basis of memories, thoughts, and skills.
In AD, information transfer at the synapses begins to fail, the number of synapses declines, and eventually cells die. Brains with advanced AD show dramatic shrinkage from cell loss and widespread debris from dead and dying neurons.
Symptoms of AD
AD can affect different people in different ways, but the most common symptom pattern begins with gradually worsening difficulty in remembering new information. This is because disruption of brain cells usually begins in regions involved in forming new memories. As damage spreads, individuals experience other difficulties. The following are warning signs of AD:
- Memory loss that disrupts daily life.
- Challenges in planning or solving problems.
- Difficulty completing familiar tasks at home, at work, or at leisure.
- Confusion with time or place.
- Trouble understanding visual images and spatial relationships.
- New problems with words in speaking or writing.
- Misplacing things and losing the ability to retrace steps.
- Decreased or poor judgment.
- Withdrawal from work or social activities.
- Changes in mood and personality.
In advanced AD, people need help with bathing, dressing, using the bathroom, eating, and other daily activities. Those in the final stages of the disease lose their ability to communicate, fail to recognize loved ones, and become bed-bound and reliant on 24/7 care. The inability to move around in late-stage AD can make a person more vulnerable to infections, including pneumonia (infection of the lungs). AD is ultimately fatal, and AD-related pneumonia is often the cause.
Although families generally prefer to keep the person with AD at home as long as possible, most people with the disease eventually move into a nursing home or another residence where professional care is available.
Risk factors for AD
Although the cause or causes of AD are not yet known, most experts agree that AD, like other common chronic conditions, probably develops as a result of multiple factors rather than a single cause.
The greatest risk factor for AD is advancing age, but AD is not a normal part of aging. Most Americans with AD are aged 65 or older, although individuals younger than age 65 can also develop the disease.
When AD or another dementia is recognized in a person under age 65, these conditions are referred to as “younger-onset” or “early-onset” AD or “younger-onset” or “early-onset” dementia.
A small percentage of AD cases, probably less than 1%, are caused by rare genetic variations found in a small number of families worldwide. These variations involve chromosome 21 on the gene for the amyloid precursor protein, chromosome 14 on the gene for the presenilin 1 protein, and chromosome 1 on the gene for presenilin 2. In these inherited forms of AD, the disease tends to develop before age 65, sometimes in individuals as young as 30 years.
A genetic factor in late-onset AD (AD developing at age 65 or older) is apolipoprotein E [4 (APOE [4). APOE [4 is one of the three common forms of the APOE gene, which provides the blueprint for a protein that carries cholesterol in the bloodstream. Everyone inherits one form of the APOE gene from each of his or her parents. Those who inherit one APOE [4 gene have increased risk of developing AD. Those who inherit two APOE [4 genes have an even higher risk. However, inheriting one or two copies of the gene does not guarantee that the individual will develop AD.
A significant portion of people with mild cognitive impairment (MCI), but not all, will later develop AD. MCI is a condition in which a person has problems with memory, language, or another essential cognitive function that are severe enough to be noticeable to others and show up on cognitive tests, but not severe enough to interfere with daily life. Studies indicate that as many as 10%-20% of people aged 65 and older have MCI. People whose MCI symptoms cause them enough concern to visit a physician appear to have a higher risk of developing dementia. It is estimated that as many as 15% of these individuals progress from MCI to dementia each year. From this estimate, nearly half of all people who have visited a physician about MCI symptoms will develop dementia in 3 or 4 years. It is unclear what mechanisms put those with MCI at greater risk for developing AD or other dementia. MCI may, in some cases, represent a transitional state between normal aging and the earliest symptoms of AD.
Treatment and prevention of AD
No treatment is available to slow or stop the deterioration of brain cells in AD. The U.S. Food and Drug Administration has approved five drugs that temporarily slow worsening of symptoms for about 6-12 months, on average, for about half of the individuals who take them. Researchers have identified treatment strategies that may have the potential to change its course. Approximately 90 experimental therapies aimed at slowing or stopping the progression of AD are in clinical testing in human volunteers.
Despite the current lack of disease-modifying therapies, studies have consistently shown that active medical management of AD and other dementias can significantly improve quality of life through all stages of the disease for diagnosed individuals and their caregivers. Active management includes appropriate use of available treatment options, effective integration of coexisting conditions into the treatment plan, coordination of care among physicians and others involved in maximizing quality of life for people with AD or other dementia, and use of supportive services such as counseling, activity and support groups, and adult day center programs.
A growing body of evidence suggests that the health of the brain – one of the body’s most vascular organs – is closely linked to the overall health of the heart and blood vessels. Some data indicate that management of cardiovascular risk factors, such as high cholesterol, Type 2 diabetes, high blood pressure, smoking, obesity and physical inactivity may help avoid or delay cognitive decline. Many of these risk factors are modifiable – that is, they can be changed to decrease the likelihood of developing both cardiovascular disease and the cognitive decline associated with AD and other forms of dementia. More limited data suggest that a low-fat diet rich in fruits and vegetables may support brain health, as may a robust social network and a lifetime of intellectual curiosity and mental stimulation.
Millions of Americans now have AD or other dementia. More women than men have dementia, primarily because women live longer, on average, than men. This longer life expectancy increases the time during which women could develop AD or other dementia.
Estimates from different studies on the prevalence and characteristics of people with AD and other dementias vary, depending on how each study was conducted. Data from several studies are used in this section to describe the prevalence of these conditions and the proportion of people with the conditions by gender and years of education. Data sources and study methods are described, and more detailed information is contained in the End Notes section in the Appendices.
Prevalence of AD and other dementias
An estimated 5.3 million Americans of all ages have AD. This figure includes 5.1 million people aged 65 and older  and 200,000 individuals under age 65 who have younger-onset AD. The Alzheimer’s Association estimates that there are 500,000 Americans younger than 65 with AD and other dementias. Of these, approximately 40% are estimated to have AD.
- One in eight people aged 65 and older (13%) has AD.
- Every 70 seconds, someone in America develops AD. By mid-century, someone will develop AD every 33 seconds.
Prevalence of AD and other dementias in women and men
Women are more likely than men to have AD and other dementias. On the basis of estimates from the Aging, Demographics, and Memory Study (ADAMS), 14% of all people aged 71 and older have dementia. As shown in Fig. 1, women aged 71 and older had higher rates than men: 16% for women and 11% for men.
Estimated percentage of Americans aged 71+ with dementia. by gender, ADAMS, 2002. Created from data from Plassman et al
Further analysis of these data shows that the larger proportion of older women than men who have dementia is primarily explained by the fact that women live longer, on average, than men. Likewise, many studies of the age-specific incidence (new cases) of dementia have found no significant difference by gender.
A similar explanation is believed to be true for AD. The larger proportion of older women than men who have AD is believed to be explained by the fact that women live longer. Again, many studies of the age-specific incidence of AD show no significant difference for women and men. Thus, it appears that gender is not a risk factor for AD and other dementias when age is taken into account.
Prevalence of AD and other dementias by years of education
People with fewer years of education appear to be at higher risk for AD and other dementias than those with more years of education. Prevalence and incidence studies show that having fewer years of education is associated with a greater likelihood of having dementia and a greater risk of developing dementia.
Some researchers believe that having more years of education (compared with those with fewer years) provides a “cognitive reserve” that enables individuals to compensate for symptoms of AD or another dementia. However, others believe that these differences in education attainment and dementia risk reflect factors such as increased risks for disease in general and less access to medical care in lower socioeconomic groups.
Racial and ethnic differences in rates of AD and other dementias have also been reported and are more fully discussed in the Special Report.
Causes of dementia
Although AD is the most common form of dementia, data are emerging to suggest that the attribution of dementia to specific types may not be as clear-cut as previously believed. A study by Schneider et al reports that most older community-dwelling people (mean age at death, approximately 88 years) have changes in the brain suggestive of disease. People with dementia often have evidence of multiple types of brain disease.
Of the first 141 autopsies in this study, 80 examined brain tissue samples from people with intermediate or high likelihood of having AD based on clinical evaluation, which included medical history, neuropsychological tests, and physical examination, with an emphasis on neurologic function. Less than half of the 80 autopsies showed evidence of AD alone. Nearly a third showed evidence of AD and infarcts; 15% showed evidence of AD and Parkinson’s disease/Lewy body disease; 5% showed evidence of all three diseases; and 2.5% showed evidence of AD and a brain disease other than infarcts or Parkinson’s disease/Lewy body disease. Although 50% of participants with little or no likelihood of having AD based on clinical evaluation also had no evidence of dementia on autopsy, approximately one-third showed signs of brain infarcts. Thus, there is reason to believe that the causes of dementia may be much more complicated than originally believed.
Looking to the future
The number of Americans surviving into their 80s and 90s and beyond is expected to grow dramatically as a result of advances in medicine and medical technology, as well as social and environmental conditions. Because the incidence and prevalence of AD and other dementias increase with age, the number of people with these conditions will also grow rapidly.
- In 2000, there were an estimated 411,000 new (incident) cases of AD. For 2010, that number is projected to be 454,000 new cases; by 2030, 615,000; and by 2050, 959,000.
- This year, more than an estimated 5.5 million Americans are 85 years and older; by 2050, that number will nearly quadruple to 19 million.
- Although the number of Americans aged 100 years and older is estimated at 80,000 in 2010, by 2050 there will be more than a half million Americans aged 100 years and older.
- The 85-years-and-older population currently includes about 2.4 million people with AD, or 47% of the AD population aged 65 and older. When the first wave of baby boomers reaches age 85 years (2031), an estimated 3.5 million people aged 85 and older will have AD.
- The number of people aged 65 and older with AD is estimated to reach 7.7 million in 2030 – more than a 50% increase from the 5.1 million aged 65 and older currently affected.
- By 2050, the number of individuals aged 65 and older with AD is projected to number between 11 million and 16 million – unless medical breakthroughs identify ways to prevent or more effectively treat the disease. Barring such developments, by that date, more than 60% of people with AD will be aged 85 or older.
AD was the seventh leading cause of death across all ages in the United States in 2006. It was the fifth leading cause of death for those aged 65 and older. In the final data for 2006, AD was reported as the underlying cause of death for 72,432 people. Of note are the nearly identical numbers of deaths attributed to diabetes (the sixth leading cause of death) and AD. In fact, the preliminary data for 2006 indicated AD was the sixth leading cause of death, and diabetes the seventh; only 17 deaths separated the sixth and seventh rankings.
The underreporting of AD as an underlying cause of death has been well documented, and it occurs in both local communities and in nursing homes. Death rates from the disease can vary a great deal across states, and result from differences in state demographics and reporting practices. Death rates among people with AD dramatically increase with age. From one community-based, 15-year prospective study, the mortality rate for people aged 75-84 years with AD was nearly 2.5 times greater than for those aged 55-74 with the disease. At age 85 and older, the rate was nearly twice that of those aged 75-84 with AD. Two-thirds of those dying of dementia did so in nursing homes, compared with 20% of cancer patients and 28% of people dying from all other conditions.
Deaths from AD
Although other major causes of death continue to experience significant declines, those for AD have continued to rise. In 1991, only 14,112 death certificates recorded AD as the underlying cause . Comparing changes in selected causes of death between final data for 2000 and final data for 2006, deaths attributed to AD increased 46.1%, whereas those attributed to the number one cause of death, heart disease, decreased 11.1%. Patterns of reporting deaths on death certificates change substantially over time, however, for AD and for other causes of death. AD is a major cause of death and is clearly becoming a more common cause as the populations of the United States and other countries age. The increase in the number and proportion of death certificates listing AD may strongly reflect both changes in patterns of reporting deaths on death certificates as well as an increase in the actual number of deaths attributable to AD.
Race, ethnicity, and AD
Older African-Americans and Hispanics are considerably more likely than older whites to have AD and other dementias. Findings from different studies vary, but the available research indicates that older African-Americans are probably about 2 times more likely than older whites to have AD and other dementias. Older Hispanics are probably at least 1.5 times more likely than older whites to have these conditions.
When differences between racial and ethnic groups are found, it is sometimes assumed that the differences must be due to genetic factors, but no known genetic factors can account for the differences in the prevalence of AD and other dementias among older whites, African-Americans, and Hispanics. On the other hand, conditions such as high blood pressure and diabetes, both of which are known risk factors for AD and dementia, are more common in older African-Americans and Hispanics than in older whites and probably account for some of the differences in prevalence of AD and other dementias among these groups. Likewise, lower levels of education and other socioeconomic characteristics that are associated with increased risk for AD and other dementias are more common in older African-Americans and Hispanics than in older whites, and probably also account for some of the differences in prevalence among the groups.
This special report provides information about the prevalence of AD and other dementias by race and ethnicity, and the factors that are associated with and probably account for some of the differences in prevalence among whites, African-Americans, and Hispanics. The report also provides information about the extent to which AD and other dementias are diagnosed in different racial and ethnic groups, the proportion of older Medicare beneficiaries with AD and other dementias by race and ethnicity, and differences in the use and costs of medical services for older white, African-American, Hispanic, and other Medicare beneficiaries with these conditions.
To develop this report, the Alzheimer’s Association convened an Expert PanelA14 and reviewed findings from published studies. The Association also contracted for information from the 2006 Health and Retirement Study (HRS) survey, a large-scale survey of a nationally representative sample of older Americans, and obtained new Medicare data on the proportion of older Medicare beneficiaries with AD and other dementias by race and ethnicity and the use and costs of medical services in different racial and ethnic groups.
Ideally, information about the prevalence of AD and other dementias in different racial and ethnic groups would be based on studies that conducted a standardized diagnostic evaluation to identify people with these conditions and included a nationally representative sample large enough to allow for valid estimates of prevalence by race and ethnicity. The only such study completed to date is ADAMS, which provides information about the prevalence of AD and other dementias in whites and African-Americans aged 71 and older. Findings from ADAMS show that African-Americans aged 71 and older are almost 2 times more likely than whites in the same age group to have AD or other dementia (21.3% of African-Americans compared with 11.2% of whites).
To estimate the prevalence of AD and other dementias in white and African-American people aged < 71 years and Hispanics of any age, this report uses findings from other studies that conducted a standardized diagnostic evaluation to identify people with AD and other dementias and included a sample representative of the population of a given geographic area. The report uses findings from the HRS, which pertain to cognitive impairment rather than AD or dementia specifically, to provide a broad national context and foundation for thinking about the prevalence of cognitive impairment, AD, and other dementias in the United States, and about the health and socioeconomic factors that probably account for some of the differences in prevalence among racial and ethnic groups.
From 2010 to 2050, as the total number of Americans aged 65 and older increases from 40 million to 89 million, the proportion of older Americans in different racial and ethnic groups is expected to change markedly. In 2010, whites constitute about 80% of the U.S. population aged 65 and older, African-Americans about 9%, and Hispanics about 7%. Other racial and ethnic groups, including Asian-Americans, American Indians and Alaskan Natives, and Native Hawaiians and Pacific Islanders, constitute the remaining 4%. In 2050, it is expected that whites will constitute a smaller proportion of the older population (59%), African-Americans a larger proportion (12%), Hispanics a much larger proportion (20%), and other racial and groups the remaining 9%. Improved understanding about the prevalence of AD and other dementias in different racial and ethnic groups and the factors that are associated with and probably account for some of the differences in prevalence among these groups is essential for addressing the needs of people with these conditions and their families now and in the future.
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Source: Alzheimer’s & Dementia: The Journal of the Alzheimer’s Association
Volume 6, Issue 2 , Pages 158-194, March 2010