March 24, 2010
Seniors who feel drowsy much of the time, or who have periods when they stare into space or their thinking seems illogical or disorganized, may be at increased risk of Alzheimer's disease, a new study reports. The findings were published in Neurology, the medical journal of the American Academy of Neurology.
"If you have these lapses, they don't by themselves mean that you have Alzheimer's," said James Galvin, M.D., a Washington University neurologist at Barnes-Jewish Hospital and a senior author of the study. "Such lapses do occur in healthy older adults. But our results suggest that they are something your doctor needs to consider if he or she is evaluating you for problems with thinking and memory."
''These mental lapses, or cognitive fluctuations, are common in a type of dementia called dementia with Lewy bodies, but researchers previously did not know how frequently they occurred in people with Alzheimer's disease.
The study involved 511 people with memory problems whose average age was 78. Researchers interviewed each participant and a family member, evaluated the participants for dementia and tested their memory and thinking skills.
People with three or four of the following symptoms met the criteria for having mental lapses:
* Feeling drowsy or lethargic most of the time, or several times per day, despite getting enough sleep the night before.
* Sleeping two or more hours before 7 p.m.
* Having times when the person's flow of ideas seems disorganized, unclear or not logical.
* Staring into space for long periods.
About one in eight, or 12 percent, of the participants had at least three of these symptoms, meeting the criteria for cognitive fluctuations. Those with mental lapses were 4.6 times more likely to be diagnosed with Alzheimer's.
Of 216 of those diagnosed with very mild dementia, 25 had mental lapses; of the 295 with no dementia, only two had mental lapses. In addition, participants with mental lapses did worse on tests of memory and thinking than people without mental lapses.
"When older people are evaluated for problems with their thinking and memory, doctors should consider also assessing them for these mental lapses," Dr. Galvin said. "We have some ideas about why the biology of dementia with Lewy bodies causes these mental lapses, but nothing comparable for Alzheimer's. It's possible that some of the patients who were diagnosed with Alzheimer's disease in this study will go on to develop dementia with Lewy bodies, but at the time of the study, they weren't showing any of the Lewy body dementia's core features."
''Lewy body disease is a form of dementia that causes clumps of proteins known as Lewy bodies to form in brain cells. It is less common than Alzheimer's, but some people have features of both diseases, as well as other neurologic ailments like Parkinson's disease. Pronounced mental fluctuations are a hallmark of Lewy body dementia, as are visual hallucinations. A doctor can help to distinguish between features of these diseases.
Adriana Escandon, MD, Noor Al-Hammadi, Mb, ChB, MPH James E. Galvin, MD, "Effect of cognitive fluctuation on neuropsychological performance in aging and dementia." Neurology, Vol. 74, Jan. 18, 2010; pages 210-217. Washington University School of Medicine, press office.