When you stride into a room only to forget the reason why, you've experienced a lapse in prospective memory-the ability to recall future plans. For most, this is merely an occasional annoyance, but a new study suggests that the problem becomes much worse in older people who carry a genetic risk factor for developing Alzheimer's disease. The work may help physicians identify and treat Alzheimer's at an earlier stage.
Catching Alzheimer's at its beginnings is important for treatment as well as for helping scientists understand how the disease progresses. Studies have shown that people with the ε4 allele of APOE-a gene involved in cholesterol transport—are up to 8 times more likely to develop Alzheimer's disease than noncarriers. However, no one had examined the connection between the allele and loss of prospective memory, a common problem anecdotally reported in the early stages of Alzheimer's.
To test the connection, Mark McDaniel, a psychologist at Washington University in St. Louis, and colleagues asked 16 older, dementia-free carriers and 16 noncarriers to write down a specific word, such as spaghetti, every time they saw another specific word, such as chair. When comparing the results, the researchers discovered that APOE ε4 carriers failed to remember to write down the second word 3 times more often than the noncarriers did.
But had the subjects failed to recall the instructions (i.e. had a lapse in prospective memory) or simply forgotten the second words? To find out, the researchers mentioned the first words and asked the subjects if they remembered the second words. All participants knew them.
According to McDaniel, this confirms that the APOE ε4 carriers failed to remember the instructions, not the word association, and thus had a loss of prospective memory. In the future, physicians may want to target carriers to help them improve their prospective memory, says McDaniel, who reports the findings in the January issue of Neuorpsychology.
George Bartzokis, a neurologist at the University of California, Los Angeles (UCLA), agrees that the work could help catch Alzheimer's early. And "the earlier we can study the process, the earlier we can come up with treatment," he says. But Susan Bookheimer neuropsychologist also at UCLA, questions if the team used the best tests to determine that the subjects were actually dementia-free and wonders if some of them might have already been in the early stages of Alzheimer's disease.