Forgetting first words on a list may signal mental decline

A reduced ability to remember words at the start of a list may be an early sign of mental decline, a new study suggests.

During the study, older adults who had trouble remembering the first four of 15 words on a list were more likely to score worse on a test of cognition four years later than people who had less trouble remembering the words.

In general, people remember words at the beginning of a list (known as primacy words) better than those in the middle. This so-called primacy effect may be due to the fact that people tend to go over words at the beginning of a list more frequently, and better commit them to memory, than they do middle words. Previous studies have found that damage to a part of the brain called the hippocampus dampens the primacy effect. (The hippocampus is thought to be involved in memory formation.) People generally remember words at the end of the list better than words in the middle as well — a phenomenon called the recency effect.

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The new findings suggest that a person's inability to remember words at the beginning of a list may be a red flag for the risk of later mental decline, the researchers said.

If the findings are confirmed by future studies, such a test could be a non-invasive way to identify older adults at risk for subsequent cognitive decline, said study researcher Dr. Nunzio Pomara, director of the geriatric psychiatry division at the Nathan S. Kline Institute for Psychiatric Research, in Orangeburg, N.Y. People in the earliest stages of cognitive decline may be able to benefit from treatments to prevent the condition, which are being tested now, Pomara said.

The study involved about 200 people ages 60 to 91 who showed no signs of dementia or psychiatric illness at the study's start. The study participants were read a list of 15 words five times, and then asked to remember the words immediately after hearing them. Twenty minutes later, they were again asked to remember the words. Everyone also took a test to assess cognitive function, and returned several times during the following years to complete the same test.

Nearly 70 people experienced a decline in their cognitive test scores during the course of the four-year study. Those who initially had trouble remembering primacy words after the 20-minute wait were more likely to have a drop in their scores.

There was no link between the ability to remember words at the end of a list and scores on cognitive tests,  Pomara said.

The researchers note that the mental decline experienced by the people in this study was subtle, which might be expected considering that no one had serious cognitive problems when the study began and participants were followed for a short time. Larger studies of people with a greater degree of cognitive impairment are needed, the researchers said.

The new study is published  in the March issue of the journal Archives of Clinical Neuropsychology.

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