(CBS) Can't put a name to a famous face? It may be an sign of a type of dementia.
Researchers have devised a basic test using photographs of famous people like Albert Einstein, Bill Gates or Oprah Winfrey that they claim may be able to identify early dementia in people 40 to 65 years old.
They tested 30 people with primary progressive aphasia (PPA), a rare kind of early-onset dementia that occurs when parts of the brain degenerate to cause problems in speech and language. The researchers also looked at 27 people without dementia that acted as controls.
PPA is more common in adults under the age of 65, but it can develop any time, according to Northwestern University Feinberg School of Medicine. The participants were around 62 years old on average.
"People with this type of dementia consistently forget names of famous people they once knew -- it's more than forgetting a name or two of a famous person," senior author Emily Rogalski, an assistant research professor at the Cognitive Neurology and Alzheimer's Disease Center at the Northwestern University Feinberg School of Medicine in Chicago, told USA Today.
The subjects were shown 20 black and white pictures of famous faces, including John F. Kennedy, Lucille Ball, Princess Diana, Martin Luther King, Jr. , Liza Minnelli, Pope John Paul II, Bill Clinton, Humphrey Bogart, Ronald Regan and Elvis Presley. They were given a point each time they could give the person's name. If they couldn't remember the name, the subjects were awarded a point if they could describe at least two accurate facts about the person in the picture.
In addition, all the people tested had MRI brain scans completed on them.
The researchers discovered that people with early-onset dementia performed worse on the test, scoring an average of 79 percent when it came to recognizing the people and 46 percent when they were asked to recall their names. Those without dementia remembered 97 percent of the subjects and could name them in 93 percent of the cases.
The MRI scans revealed that people who had a hard time remembering names were more likely to have a loss of brain tissue in the left temporal lobe of the brain. Those who had difficulty recalling who the famous people even were had tissue losses on both sides of their temporal lobes.
"In addition to its practical value in helping us identify people with early dementia, this test also may help us understand how the brain works to remember and retrieve its knowledge of words and objects," study author Tamar Gefen, a clinical psychology doctoral student at Northwestern University Feinberg School of Medicine in Chicago, said in a press release. "These tests also differentiate between recognizing a face and actually naming it, which can help identify the specific type of cognitive impairment a person has," she added.
Dr. Marie Janson, director of development for Alzheimer's Research UK, said to the BBC that it is important to diagnose people with dementia so they can get the proper treatment, but it is often difficult to figure out which type of the disease they have.
"Studies such as this could increase our understanding of the way the brain is affected by different forms of dementia, but we must invest in research if results like these are to be used to move towards better diagnosis," she explained.
Catherine Roe, an instructor in neurology at the Washington University School of Medicine, in St. Louis, was cautious when speaking of the findings to HealthDay.
"To help us know how to use this test as a screening tool," Roe said, "more research needs to be done to figure out whether this test distinguishes all people with dementia from people without dementia or whether it distinguishes only people with one particular type of early-onset dementia from people without dementia."
The study was published in Neurology on Aug. 13.
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