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Alzheimer's Disease Health Center

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More Than 3 Million Have Dementia

Nearly 1 in 7 Adults Aged 71 and Older Have Dementia; Alzheimer's Is the Most Common Type of Dementia
WebMD Health News
Reviewed by Louise Chang, MD

Oct. 31, 2007 -- Almost one in seven U.S. adults aged 71 and older -- about 3.4 million people -- have dementia, a new study shows

Most of those elders with dementia -- 2.4 million people -- have Alzheimer's disease, according to Duke University's Brenda Plassman, PhD, and colleagues.

They reviewed data on a nationally representative group of 856 people aged 71 and older, including people in nursing homes.

The elders took tests of mental skills including memory, language, and attention to screen for dementia. They also provided blood samples and noted their depression, medications, medical history, and family history of memory problems.

The findings:

  • Almost 14% of the participants had dementia.
  • About 10% had Alzheimer's disease.
  • Dementia became more likely with age.

Dementia was more likely for people with a gene glitch linked to Alzheimer's disease, less likely for highly educated people, and equally likely for men and women.

Plassman and colleagues also combined their findings with results from previous dementia and Alzheimer's disease statistics in people as young as 60.

"This resulted in an estimated total of 3.8 million individuals with dementia and just over 2.5 million with Alzheimer's disease in the USA," write the researchers.

They note that the only previous national estimate of dementia prevalence was 2.9 million people with dementia.

As the U.S. population ages, dementia will likely become more common, Plassman's team predicts. However, dementia isn't a normal part of aging.

The dementia statistics study appears online in Neuroepidemiology.

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