More Than 3 Million Americans Have Dementia

December 2007 - Research from the University of Michigan and Duke University Medical Center published in Neuroepidemiology has found that about 3.4 million Americans over the age of 70 (13.9 per cent) suffer from some form of dementia of whom about 2.4 million (9.7 per cent) have Alzheimer's disease. The study confirmed the increased prevalence of dementia with age, from 5 per cent of people aged between 71 and 79 to 37.4 per cent of those aged 90 and older.

Funded by the National Institute on Aging, the research was based on data from 856 men and women who participated in the Aging, Demographics and Memory Study conducted in 2002 as part of the larger University of Michigan Institute for Social Research (ISR) Health and Retirement Study, a nationally representative survey of Americans aged 51 and older.

Lead author Brenda Plassman said:

"These conditions affect millions of older Americans and touch nearly every family in some way, and the situation is only going to get worse as the population ages."

Researchers explain that this study is believed to be the first to draw on a nationally representative sample, thus allowing policymakers and care providers to improve care plans for patients with dementia and their families and assisting in assessment of treatment advances.

Richard Suzman, director of the Behavioral and Social Research Program at the National Institute on Aging commented:

"These data about dementia are linked to an enormous wealth of economic, health, psychological, and other information about these same individuals and their families over time. We can now track the impact and costs of dementia on society, the economy, and families in ways we never could before."

Participants were assessed at home by a specialist nurse and neuropsychology technician, using a protocol similar to memory evaluation studies conducted in clinical settings. Information was provided about a participant's daily functioning by someone close to them, usually a family member or friend. Neuropsychological tests were administered including assessments of memory, orientation, language, attention and problem solving ability. Cheek swabs provided DNA samples to test for the APOE e4 allele, linked to an increased risk of developing Alzheimer's disease. Data were reviewed by Duke clinicians and final diagnoses made by a independent expert panel.

Researchers found that Alzheimer's disease accounted for approximately 69.9 per cent of all cases of dementia, with vascular dementia (often caused by stroke) accounting for 17.4 per cent. The prevalence of Alzheimer's disease increased with age comprising 79.5 per cent of dementia cases in people over 90 compared to 46.7 per cent among those in their 70s. The study found that the more years of education completed, the lower the risk of dementia. After controlling for education and age, they found no significant gender difference in dementia risk. The study confirmed that the presence of one or two APOE e4 alleles was associated with a significantly higher risk of developing dementia.

Current findings were combined with earlier studies using 60 as a minimum age resulting in an estimated total of 3.8 million people with dementia, including just over 2.5 million with Alzheimer's disease. A previous national prevalence estimate (obtained by extrapolating from regional samples) was 2.9 million.

Co-author Kenneth Langa explained:

"Our study finds that the prevalence of dementia is about 30 per cent higher than this estimate."

William Thies, vice president of Medical and Scientific Relations at the Alzheimer's Association commented:

"What this study and others before it confirm is that there are millions of Americans living with Alzheimer's and dementia, and that number is estimated to grow at an epidemic rate if we don't do something about it. The nation's leaders need to act now to advance research for effective treatments and provide care and support to those living with Alzheimer's."

David Weir, director of the ISR Health and Retirement Study added:

"As the elderly population in the United States grows, the number of individuals with dementia will certainly increase tremendously. Planning for the long-term care needs of this vulnerable population will become increasingly important. This new data, used along with related data from the Health and Retirement Study, should increase our nation's ability to successfully meet the needs of an aging U.S. population and those who love them."

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