November 26, 2007
A new survey found that one in seven Americans over 70 have Alzheimer's or another form of dementia. And the older you are, the more likely you are to have dementia. The findings highlight the growing prevalence of a disease that afflicts more and more seniors in an aging population and the urgent need to find effective treatments and a cure.
The survey results, from researchers at the University of Michigan and Duke University in North Carolina, come from a nationwide sampling of 856 men and women from across the United States. The results indicate that about 3.4 million men and women aged 71 and up have some type of dementia.
The prevalence of Alzheimer's and other forms of dementia increased dramatically with age. About five percent of those 71 to 79 had dementia, compared to 37.4 percent, or more than one in three, of those age 90 and older. This differs somewhat from previous estimates of about 50 percent for those over 85. Alzheimer's is by far the most common form of dementia, accounting for 2.4 million cases in the seniors surveyed. That accounts for almost one in ten seniors in their 70s, 80s, and older and amounts to nearly 5 million nationwide. The next most frequent cause of dementia was memory loss due to strokes and vascular disease.
"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," said Duke University researcher Brenda Plassman, the lead author of the article, which appeared in the November 2007 issue of Neuroepidemiology.
"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," said Richard Suzman, director of the Behavioral and Social Research Program at the National Institute on Aging. "We can now track the impact and costs of dementia on society, the economy, and families in ways we never could before."
In the study, nurses and technicians assessed study participants in their homes using tests of memory, language and problem solving skills. Close friends and family members were also questioned about participants' memory and ability to perform everyday tasks. In addition, DNA samples were collected from a cheek swab to test for the presence of the APO-E4 gene, which has been linked to an increased risk of developing Alzheimer's disease.
Overall, the researchers found that Alzheimer's disease accounted for almost 70 percent of all dementias. The percentage of cases due to Alzheimer's increased from almost half of dementia cases among people in their 70s to almost 80 percent among those in their 90s. Vascular dementia accounted for 17.4 percent of cases overall. The researchers also examined how education, gender, and the presence of the APOE-E4 gene were related to dementia. They found that the more years of education, the lower the risk of dementia. After controlling for education levels and age, they found no significant difference in dementia risk between males and females. As expected, they found that the presence of one or two APOE-E4 genes was linked with significantly higher risk of developing dementia.
The findings are consistent with earlier estimates that the prevalence of Alzheimer's is rising rapidly as the population grows older. Unless an effective treatment is found, up to 16 million people will suffer from Alzheimer's by 2050. Current treatments for Alzheimer's may provide temporary relief of symptoms, but they do nothing to stop the relentless downward progression of disease.
The Fisher Center for Alzheimer's Research Foundation continues to fund vital research into the underlying causes of Alzheimer's and the search for a cure. To learn more or to make a donation, visit www.ALZinfo.org.
University of Michigan. November 2007 issue of Neuroepidemiology.