Friday July 5 2013
Activities such as reading may slow cognitive decline
“Reading keeps your brain fit and helps fight off dementia,” the Daily Express reports.
The claim is based on a small US study in which older adults had annual tests of brain function during the last six years of their lives and completed questionnaires on their cognitive activities throughout their life.
Examples of cognitive activities listed in the study included:
- writing letters
- visiting a library
- seeking or processing information
After death, all participants had brain autopsies to look for signs that they had any of the different forms of dementia.
The research found that self-reported cognitive activity, both in later life and in early life, were associated with a slower rate of cognitive decline in each year prior to death.
Several factors affect the conclusions we can draw from this research, including its small size, reliance on self-reporting and failure to account for other confounders that could influence dementia risk.
Nevertheless, seeing that activities such as reading books are cheap, risk-free and can bring a great deal of enjoyment to your life, we recommend you pick up a library card if you haven’t done so already.
Where did the story come from?
The study was carried out by researchers from Rush University Medical Center, Chicago, US and was funded by the National Institute on Aging and the Illinois Department of Public Health.
The study was published in the peer-reviewed medical journal Neurology.
The media fairly reflects the findings of this research, but fails to note its limitations, including the small, selected sample and possibilities of inaccurate cognitive activity recall.
What kind of research was this?
This was a cohort study which aimed to test the theory that cognitive activity over a person’s lifetime is associated with the rate of decline in cognitive function in later life.
This involved looking at a sample of older adults, and prospectively giving them cognitive function tests each year to look at the rate of decline.
After they died, the researchers examined their brains to look for physical signs of dementia, such as areas of “infarcts” (where the brain had been starved of oxygen) which are often associated with vascular dementia. They also looked for the abnormal ‘clumps’ of protein (amyloid plaques) and fibres (tau tangles) associated with Alzheimer’s disease.
The researchers then compared the association between participants’ cognitive decline in later years and brain changes after death, to their recall of cognitive tasks earlier in life.
This study can show associations, but cannot prove conclusively whether cognitive activity can directly preserve your cognitive function. Aside from the small sample size and the problems with self-reporting, there could be other confounding effects from other unmeasured factors.
What did the research involve?
This research used data from people taking part in the Rush Memory and Aging [sic] Project who did not have dementia study start. Eligible participants were those aged over 55 years who agreed to have clinical examinations (including cognitive testing) every year from 1997 onwards, and who agreed to have a brain autopsy when they died.
The sample for this study included 294 people who, by October 2012, had died and undergone brain autopsy and who had annual cognitive function information available. The average age at death was 89 years, and 68% were women. At the time of enrolment in the study, 37% had mild cognitive impairment. The average follow-up for each person from enrolment to death was 5.8 years.
Lifetime cognitive activity was assessed at the time of enrolment using a 37-item questionnaire. This covered activities such as reading books, visiting a library, and writing letters, and activities that involved seeking or processing information with response categories from 1 (once a year or less) to 5 (every day or about every day). Seven later-life activities were assessed (at the time of enrolment), plus:
- 11 childhood activities (age 6–12 years)
- 10 activities around young adulthood (age 18 years)
- nine activities around middle age (age 40 years)
Cognitive testing was performed every year though 19 tests of cognitive performance, including measures of different types of memory, speed of perception, and of visuospatial activity (the ability to analyse and understand physical space, such as using a map to navigate through a foreign city).
A decline in cognitive function was classified as either one of two outcomes:
- a confirmed diagnosis of dementia – which was defined as a history of cognitive decline and impairment in at least two cognitive domains
- mild cognitive impairment (MCI) – no previous history of cognitive impairment but current impairment in one or more cognitive domains
The last examination had been performed on average 7.7 months before the person’s death.
The brain autopsy after each person’s death included examining for signs of infarcts and the classic protein plaques or tangles associated with Alzheimer’s disease. They also looked for Lewy bodies, which are a distinctive type of protein deposit inside brain cells. People who have dementia with Lewy bodies (DLB) tend to have both Alzheimer’s and Parkinson’s disease-like symptoms.
What were the basic results?
Self-reported cognitive activity in both earlier and later life were associated with higher educational achievement, but were not related to age at death or to gender.
During follow up, 102 people developed dementia (35%), and 51 developed MCI (17%).
On brain autopsy after death:
- a third had one or more larger areas of infarct in their brain
- just under a quarter had one or more tiny areas of infarct
- a tenth had Lewy bodies
In models adjusted for brain autopsy findings, age at time of death, gender and educational level, a higher level of later-life cognitive activity (assessed at the time of enrolment) was associated with a higher level of cognitive function and a slower rate of cognitive decline.
Results were similar for earlier-life cognitive activity: those with more frequent early life cognitive activity had a slower rate of cognitive decline.
However, unlike later life cognitive activity, early life cognitive activity was not associated with cognitive function at the time of enrolment.
The researchers estimate that just under 15% of the variability in cognitive decline is not attributable to brain autopsy findings and could be due to previous cognitive activity.
How did the researchers interpret the results?
The researchers say that, independently of brain changes on autopsy, more frequent lifetime cognitive activity is associated with a slower rate of cognitive decline in later life.
This research in 294 adults in the latter six years of their life, shows that self-reported cognitive activity, both in later life (at the time of enrolment) and in early life, were associated with a slower rate of cognitive decline each year.
The cohort study has various strengths:
- it used numerous validated tests to assess cognitive function prospectively on an annual basis
- it used an extensive questionnaire to assess levels of cognitive activity (such as reading and writing)
- it carried out brain autopsies after death to confirm clinical diagnoses of dementia
However, it does also have limitations. It was relatively small, including just under 300 people, all of whom had responded to recruitment calls within the Chicago area and had to agree to have a brain autopsy. The sample may have been distorted by selection bias. People motivated enough to volunteer to take part in a clinical trial may not be generalisable to the whole population
The study also relied on retrospective self-reports of cognitive activity. This required the elderly participants to recall their levels of activity as far back as childhood, which may not be entirely accurate. Those with poorer cognitive abilities may have had more problems remembering their past cognitive activity, and this would bias results. There is also the possibility that other health lifestyle and socioeconomic factors, besides educational level, that have not been taken into account are influencing the results.
Overall, this study cannot provide conclusive proof that greater cognitive activity directly prevents development of mild cognitive impairment or diagnoses of dementia. Nevertheless, the findings that more frequent cognitive activity may slow the rate of cognitive decline is consistent with prior research findings, as the authors say.
Even if frequent cognitive activity cannot slow the rate of cognitive decline, activities such as reading, writing and visiting the library may help to improve quality of life.
Analysis by Bazian. Edited by NHS Choices. Follow Behind the Headlines on Twitter.