Researchers at the University of California- Los Angeles (UCLA) have revealed that people in early stages of Alzheimer's disease have trouble focusing on what is important to remember.
"One of the first telltale signs of Alzheimer's disease may be not memory problems, but failure to control attention," said lead researcher Alan Castel, UCLA assistant professor of Psychology.
The study consisted of three groups-109 healthy older adults (68 of them female), with an average age of just under 75; 54 older adults (22 of them female) with very mild Alzheimer's disease, who were functioning fine in their daily lives, with an average age of just under 76; and 35 young adults, with an average age of 19.
All participants were presented with eight lists of 12 words, one word at a time, each paired with a point value from 1 to 12. A new word with its value was presented on a screen every second. The words were common, like "table," "wallet" and "apple."
The participants were given 30 seconds to recall the words, and were told to maximize their scores by focusing on remembering the high-value words.
They found that the young adults were selective, as they remembered more of the high-value words than the low-value words.
They recalled an average of 5.7 words out of 12, while the healthy older adults remembered fewer words, an average of 3.5, but were equally selective in recalling the high-value words.
"It's not surprising that the older adults recalled fewer words. Memory capacity declines with age. However, the older adults were just as selective as the younger adults," said Castel.
The people with very mild Alzheimer's disease recalled an average of just 2.8 words, and had some trouble in focusing on just the high-value words, recalling some lower-value words.
"They recall fewer words and their ability to be selective is worse. They understand that they should attend to the high-value words, but they can't do it as well," said Castel.
He added: "Memory can be a limited resource. If we can recall only so much information, we need to be selective in old age. A trick for successful aging is to know what the important things are and to remember those things. Many older adults learn to be more selective because they know they can't remember everything. The ability to be selective might decline when our attention is divided and in the early stages of Alzheimer's disease."
The research has been published in the journal Neuropsychology.