|One in Seven Americans Age 71 and Older Has
Some Type of Dementia, NIH-Funded Study Estimates
A new analysis suggests that about 3.4 million Americans age 71
and older — one in seven people in that age group — have
dementia, and 2.4 million of them have Alzheimer's disease (AD).
The study, supported by the National Institutes of Health (NIH),
is the latest in a series of analyses attempting to assess the
prevalence of dementia and AD, the most common form of dementia.
Published online this week in Neuroepidemiology, the study
is the first to estimate rates of dementia and AD using a nationally
representative sample of older adults across the United States.
Brenda L. Plassman, Ph.D., of Duke University Medical Center,
with Kenneth M. Langa, M.D., Ph.D., and David R. Weir, Ph.D., of
the University of Michigan, Robert B. Wallace, Ph.D., of the University
of Iowa, and others, conducted the analysis as part of the Aging,
Demographics and Memory Study (ADAMS). ADAMS is a sub-study of
the larger Health and Retirement Study (HRS), the leading resource
for data on the combined health and economic circumstances of Americans
over age 50. ADAMS and the HRS are sponsored by the National Institute
on Aging, a component of NIH, under a cooperative agreement with
the University of Michigan.
The study highlights the nationwide reach of dementia, which affects
not only those with the disease, but their families and communities
as well. "As the population ages during the next few decades,
the prevalence of Alzheimer's disease will increase several-fold
unless effective interventions are discovered and implemented," said
NIA Director Richard J. Hodes, M.D. "These data underscore
the urgency of research in this area."
The study included 856 HRS participants age 71 and older from
42 states in 2001-2003. ADAMS interviewers from Duke University
Medical School conducted at-home evaluations to gather information
about each participant's cognitive and functional status and symptoms,
neuropsychiatric symptoms, current medications, medical history
and family history of memory problems. Prior neuroimaging and laboratory
results were also obtained.
A team of clinicians reviewed the evaluation information and made
a preliminary assessment of each person's cognitive status. A consensus
panel of other medical experts then used well-accepted diagnostic
criteria to determine if the participant had normal cognitive function,
cognitive impairment without dementia, or dementia. Such criteria
further were used to discern the type of dementia, including AD
or vascular dementia, the second most common cause of dementia
in older adults.
Based on the experts' classifications, Drs. Plassman and Langa
and co-authors estimated the national prevalence and total numbers
of people age 71 and older, by age group, with any dementia and
with AD or vascular dementia in 2002. According to their calculations,
13.9 percent of Americans age 71 and older have some type of dementia,
9.7 percent of Americans in that age group have AD, and 2.4 percent
have vascular dementia. AD accounted for about 70 percent of all
dementia cases among people 71 and older.
As in other studies, the ADAMS analysis showed that the prevalence
of dementia increases significantly with age. Five percent of people
ages 71 to 79, 24.2 percent of people 80 to 89, and 37.4 percent
of those 90 years or older were estimated to have some type of
dementia. The estimated rate of Alzheimer's also rose greatly with
older age — from 2.3 percent of people ages 71 to 79 to 18.1
percent of people 80 to 89 to 29.7 percent of those age 90 and
older. The ADAMS investigators found fewer years of education and
the presence of at least one APOE e4 allele, a genetic risk factor
for AD, to be strong predictors of AD and other dementias.
Richard Suzman, Ph.D., director of NIA's Behavioral and Social
Research Program, which jointly directs the HRS, said the ADAMS
data will prove particularly valuable not only in assessing the
prevalence of dementia, but also its impact. "ADAMS, with
its link to the data about the health, economic, and family resources
of individuals in the study, will help us to characterize more
fully the burden of dementia on individuals, caregivers and the
nation's health care system," he says.
The ADAMS report is the latest published study to estimate the
prevalence of dementia and AD among older Americans. "These
assessments have provided a range of estimates, based on differing
methodologies and approaches," explains Dallas Anderson, Ph.D.,
program director for population studies in NIA's Dementias of Aging
Branch. For example, some studies have included lower age ranges
than ADAMS or broader characterizations of dementia, or have sampled
participants in a specific community as a base for national extrapolations.
A study reported in 1998 (Brookmeyer et al., 1998) combined incidence
data from four community-based studies, estimating that national
Alzheimer's prevalence among individuals age 60 years or older
would rise from 2.3 million in 1997 to 8.6 million in 2047. Widely
cited estimates based on the prevalence of Alzheimer's disease
in a Chicago-based community (Hebert et al., 2003), and an earlier
comparable study using data from East Boston (Evans et al., 1990)
forecast the number of those age 65 or older with AD to be 5.1
million in 2010.
Despite the varied approaches and findings, however, NIA experts
point out, the numbers of people with dementia, and Alzheimer's
specifically, will certainly increase until ways to delay the progression
or prevent the dementia are found. Advancing age is the most common
known risk factor for Alzheimer's disease.
The HRS is an ongoing national survey of 22,000 adults age 51
and older that began in 1992, providing data that helps researchers,
policy makers and others understand the life circumstances of older
adults and help address the challenges of the nation's rapidly
aging population. The ADAMS and HRS data are made publicly available
to researchers seeking to conduct studies about the older U.S.
population. For further information about the HRS and ADAMS, visit hrsonline.isr.umich.edu or www.nia.nih.gov/ResearchInformation/HRS.htm.
To reach the investigators, contact Diane Swanbrow, Institute
for Social Research, University of Michigan, at 734-647-9069 or firstname.lastname@example.org.
NIA leads the federal effort supporting and conducting research
on aging and the medical, social and behavioral issues of older
people, including AD and age-related cognitive change. For information
on dementia and aging, please visit NIA's Alzheimer's Disease Education
and Referral Center at www.nia.nih.gov/alzheimers,
or call 1-800-438-4380. For more general information on research
and aging, go to www.nia.nih.gov.
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new information and publications about aging and about age-related
The National Institutes of Health (NIH) — The Nation's
Medical Research Agency — includes 27 Institutes and
Centers and is a component of the U.S. Department of Health and
Human Services. It is the primary federal agency for conducting
and supporting basic, clinical and translational medical research,
and it investigates the causes, treatments, and cures for both
common and rare diseases. For more information about NIH and
its programs, visit www.nih.gov.