Memory lapses and dementia

Posted on: 24 October 2013 by Olderiswiser Editorial

NHS Choices 'Behind the Headlines' news analysis service responds to claims that memory lapses do not mean you are at risk of dementia

Memory loss and dementia'Tip-of-the-tongue' lapses aren't signs of dementia risk'," reports the Mail Online website, after a US study claims to have found no association between "tip-of-the-tongue" experiences and other symptoms often associated with dementia.

Researchers conducted a fairly complex series of analyses involving more than 700 US adults, chiefly looking at what they termed "tip-of-the-tongue" (TOT) lapses. These lapses are the frustrating feeling when you know an answer to a question but you can't think of the word. The researchers compared TOT lapses with scores on a memory test and age to see how they correlated with each other.

In general, the study found that increasing age was associated with an increased number of TOT responses. Increasing age was also associated with poorer memory scores. However, memory scores had no effect on the link between increasing age and increasing TOT responses.

The researchers' main conclusion is that the relationship between increasing age and increasing TOTs is separate from the relationship between increasing age and poorer memory scores.

Despite the headlines, this study did not assess diagnostic criteria for mild cognitive impairment or dementia, or look at future risk of these conditions. It therefore cannot prove that older adults who increasingly find they cannot immediately recall the names of places, people or things are not at an increased risk of dementia. 

Where did the story come from?

The study was carried out by two researchers from the University of Virginia in the US and was funded by the National Institute on Aging. It was published in the peer-reviewed journal, Psychological Science.

The Mail's coverage of the findings of the study was accurate, but its headline was a little optimistic. Because of the inherent limitations of this study and its brief, subjective measure of TOT experiences, it cannot reliably prove that there is no link between TOTs and dementia risk.

What kind of research was this?

Tip-of-the-tongue experiences (TOTs) is the name used in this research for those moments when the name of something, such as an object or a person's face, is known but cannot be immediately retrieved from memory. An example would be when you "know" who the hero of the Indiana Jones films is, but you just can't remember his name (it's Harrison Ford, for the record). It is often wondered whether such experiences could be a sign of memory decline.

This cross-sectional study aimed to look at a sample of adults of different ages to see whether the frequency of TOTs was associated with tests of memory, and how this correlated with age. The researchers looked at different types of TOT trigger; for example, when people were asked to name a face or a place, they were asked whether they knew the answer, didn't know, or whether it was on the tip-of-the-tongue.

But the main limitation of this study is that with its cross-sectional design, it can't reliably tell us whether TOT moments were associated with dementia or the risk of developing dementia. Researchers didn't look at whether participants currently met diagnostic criteria for mild cognitive impairment or dementia. In addition, they also did not check to see whether TOTs were correlated with current diagnoses, or follow people up over time to see whether frequency of TOTs was associated with future risk. 

What did the research involve?

The study included people taking part in the Virginia Cognitive Aging Project (VCAP). VCAP is an ongoing study where an extensive battery of cognitive tests are given to a large sample of adults between the ages of 18 and 99, and is designed to assess the effects of ageing on cognition. For the purposes of this study, TOT questions were added to the 2012 data collection of this project.

Participants performed a series of 16 cognitive tests spread across three test sessions. This included various tests of vocabulary, logical memory, word recall and paired associates. 

At the end of each session they were given a TOT task, though it was reported that participants were not presented with the TOT task if they did not complete the other tests in less than two hours:

  • In session one, the TOT stimuli were written definitions of 40 nouns and 10 verbs. An example question is: "What is the name of the building where one can view projected images of celestial bodies on the inner surface of a dome?" The researchers split these questions into what were considered to be easy and hard questions.
  • In session two, the stimuli were written descriptions of 25 people and 25 places; for example: "What is the name of the large waterfall in Zambia that is one of the seven wonders of the world?"
  • In session three, the stimuli were the faces of 25 politicians and 25 celebrities obtained from the Internet.

A varying number of participants completed each of the three sessions, but 718 adults completed at least one of the three and are therefore the sample used in this study.

For the TOT tasks, definitions of nouns and verbs, written descriptions of people and places, and pictures of the faces of politicians and celebrities were displayed on a computer. Participants were asked to provide the names of the target items.

After an attempt at identifying the item, they were asked to reply "know" if they knew the name of the item, "don't know" if they didn't, and "TOT" if they felt they knew the name but couldn't say it at that moment in time.

This was then followed by a multiple choice recognition test for each item where the correct answer was given along with three others. A TOT was scored if the participant had reported "TOT" and then picked the correct answer on the multiple choice.

What were the basic results?

The average age of the participants was 56 years and two-thirds were female. Each age decade was reported to be represented by between 32 and 208 participants, with the concentration of participants greatest for people in their 50s and 60s.

On vocabulary and memory tests (a standardised test known as the Wechsler Adult Intelligence Scale and Memory Scale), the full study sample had scores distributed just slightly above the national norm.

Overall, between 17% and 30% of items displayed in the TOT task were said to be associated with a TOT response.

There was a trend for people of increasing age to give a higher number of "know" and "TOT" responses and a lower number of "don't know" responses. However, perhaps unsurprisingly, older people gave a higher number of "don't know" responses to the faces of celebrities.

When looking at the multiple choice answers after the TOT task, as would be expected, people who said they "know" the answer were most likely to have also picked the correct answer from the four options, while people who had said they "don't know" were least likely to pick out the correct answer. People who had said "TOT" were inbetween the two: less accurate than the "know" responders, but more accurate than the "don't know" responders.

They then looked at how scores on memory tests were associated with the number of TOT responses and how this was influenced by age. Increasing age was associated with poorer memory scores. Increasing age was also associated with an increasing number of TOT responses. However, adjusting for memory score had no effect on the relationship between TOTs and age.

How did the researchers interpret the results?

As the researchers found that adjusting their analyses for memory score had no effect on the relationship between increasing age and increasing number of TOTs, their main conclusion is that "age-related increases in TOTs and age-related decreases in memory appear to be at least partially independent phenomena".

Conclusion

This study used a large sample of adults from Virginia in the US and conducted a fairly complex series of analyses looking at how scores on a memory test, a test of "tip-of-the-tongue" (TOT) lapses, and participants' age correlated with each other.

In general, it found that increasing age was generally associated with an increased number of TOT responses and poorer memory scores. However, memory scores had no effect on the link between increasing age and increasing TOT responses, which the researchers suggest means that the age-related influences upon TOT and memory are separate.

Although the study is of interest in terms of the effects of age on cognitive function, it is difficult to draw many firm conclusions from the results. The main limitation of this study is that its method of analysis and cross-sectional design can't reliably tell us whether TOT moments were associated with dementia or the risk of developing dementia.

Researchers gave people memory tests, but failed to look at whether participants already met diagnostic criteria for mild cognitive impairment or dementia. It therefore has not looked at whether TOTs were correlated with current diagnoses of dementia.

The researchers also didn't follow people up over time to see whether frequency of TOTs was associated with a future risk of developing dementia.

Importantly, although the researchers have made the best possible attempts to obtain a valid indication of TOTs, such experiences are likely to be highly subjective and vary from person to person and situation to situation. It is not known whether performance in the TOT test gave a clear indication of how frequently a person was experiencing TOTs in everyday life.

Also, despite the inclusion of a large sample of people, they all come from one geographical location. A sample of participants from outside Virginia or the US may give different results.

Dementia – in particular Alzheimer's, the most common form – is often not a preventable condition. However, from the little we do know, the following steps may help reduce your risk:

  • eating a healthy diet
  • maintaining a healthy weight
  • exercising regularly
  • not drinking too much alcohol
  • stopping smoking (if you smoke)
  • making sure you keep your blood pressure at a healthy level

There is also some evidence that people who keep their minds active may have a reduced risk. Although this has not been proven to be conclusive, picking up a book or tackling a crossword puzzle certainly can't hurt.

 

Analysis by Bazian. Edited by NHS Choices.

This content was originally published on Behind the Headlines. Behind the Headlines is an excellent resource for understanding how the media reports on health issues.

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