Mental lapses among older people occur more often in those developing Alzheimer’s disease than in their healthy peers, according to new research.

Cognitive fluctuations like excessive daytime sleepiness, staring into space and disorganized or illogical thinking are mental fluctuations that often precede Alzheimer’s, say researchers at Washington University School of Medicine in St. Louis.

"If you have these lapses, they don't by themselves mean that you have Alzheimer's," says senior author James Galvin. "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."

Researchers evaluated more than 500 older adults with memory problems. They were given standard tests of thinking and memory skills, and researchers interviewed participants and family members.

Those with mental lapses were 4.6 times more likely to be diagnosed with Alzheimer's. Of 216 diagnosed with very mild or mild dementia, 25 had mental lapses; of the 295 with no dementia, only two had mental lapses.

Galvin said further study is needed to determine the best way to include mental lapses in diagnostic procedures for Alzheimer's.