Monday July 26 2010
Symptoms but not brain changes were reduced by education
“Education ‘helps brain compensate for dementia changes,’” BBC News reported today, saying that people who stay in education longer appear to be less affected by the brain changes that occur during dementia. According to the newstory, European researchers have found that those with more education were as likely to show biological dementia signs in their brains at death but less likely to have displayed symptoms of the disease while alive.
The underlying study compared education, symptoms of dementia and post-mortem brain samples in about 900 people who donated their brains for research after death. It demonstrated that greater education was linked to reduced clinical dementia but did not have any bearing on changes in brain biology. It seems the brain will change with age regardless of education but that people with more education are more likely to compensate and therefore stave off the symptoms of dementia.
This study has some shortcomings, including how representative the small sample of people who agreed to post-mortem brain examination were to the general population. However, it will be of interest to neurologists, who must now unpick why more education can reduce clinical symptoms of dementia, but not the brain signs of dementia.
Where did the story come from?
The study was carried out by doctors and scientists from a number of research institutes; the University of Cambridge, the University of Sheffield, the University of Newcastle, the Institute of Public Health and the University of Kuopio in Finland. It was funded through several research grants, including a BUPA Foundation grant and the Marie Curie International Incoming Fellowship programme. It was published in the peer-reviewed medical journal Brain.
BBC News has covered this research in a balanced way and has sought feedback from the researchers and other experts in this field, who say this is an important study and that further research is needed to find out why an education can protect the brain from dementia.
What kind of research was this?
This cohort study was set up to determine whether more time in education reduces dementia risk by examining any potential link between time in education during earlier life, symptoms of dementia while alive and brain pathology at death.
Some studies have shown that people with higher levels of education in earlier life are at lower risk of clinical dementia during ageing. There are two theories for this observation: either that education protects against dementia-related pathology (changes in the brain), or that more-educated people may have the same brain pathology but may somehow compensate for it.
The researchers used a large sample of individuals followed over time to investigate these theories.
What did the research involve?
The data for the study is from a source called EClipSE (Epidemiological Clinicopathological Studies in Europe) that brings together data from three observational studies that started between 1985 and 1991. Upon entry to the study, the researchers recorded the participants’ number of years of education earlier in life, with some participants also providing consent for post-mortem brain donation. The total combined sample in the three studies was 20,944 people, but the EClipSE study includes only those 970 people who agreed to donate their brains after death.
As part of their original studies all participants in the final EClipSE sample were given further interviews at intervals of one to seven years to collect demographic and cognitive information and to establish the presence of dementia and other health-related conditions. Some patients were not included in the final analyses because the data about education, dementia diagnosis or age was missing.
Different aspects of brain pathology were assessed through autopsy after death and were generally scored in each study as none, mild, moderate or severe. The length of education was classed as either 0-3 years, 4-7 years, 8-11 years or 12 years and above. A statistical technique called logistic regression analysis was then used to assess whether there was a link between dementia and years in education.
As all of the people in one of the studies were over 85 years, and therefore had less education on average than those in the others studies, the researchers excluded this group from some of their analyses to see whether this made a difference to their results.
What were the basic results?
The study found that greater time in education was associated with a reduced risk of clinical dementia (that is, dementia symptoms) at death (odds ratio [OR] 0.89, 95% confidence interval [CI] 0.83 to 0.94). Brain pathology was not dependent on the amount of education received. The brains of people who had more education seemed in general to weigh more than those from people who had less education, even after adjusting for the influence of age, sex and the original study of participation.
When the researchers analysed by subgroups of different brain weights they found that, compared to those with less education, education was protective for brains of low to medium weight. This protective effect was not seen in high-weight brains.
How did the researchers interpret the results?
The researchers conclude that greater time in education did not protect individuals from developing neural degeneration or vascular neuropathology by the time they died, but that it did seem to prevent or mitigate the effect of that these biological changes had on the clinical symptoms of dementia before death.
They say the findings suggest that an understanding of the mechanisms that protect brain function in the presence of biological changes to the brain “may be of considerable value to society”.
This cohort study has assessed how time spent in education was linked to both brain pathology (that is, biological changes) and symptoms of dementia before death. These are some of the points to consider when interpreting these results:
- The three studies that combined data for the EClipSE sample had different methodologies, including different ways of determining status of clinical dementia at death. For example, one relied on interviews in the last years of life, informant interviews after death and death certificates, while another study relied on assessments by neurologists.
- Brain samples were also analysed in different ways, and in two of the three studies, those who agreed to donate their brains were older and more cognitively impaired than those who did not consent. It is difficult to anticipate how these differences may affect the overall results, but it may have introduced bias in the analysis of results.
- Education was only assessed at entry into the studies while follow up occurred many years into the future. This study is making a comment on education in early life and may not account for further or tertiary education that the participants received during the course of follow up.
- The researchers highlight some other shortcomings with their research including the fact that they did a number of subgroup analyses and did not adjust for these multiple comparisons. This may increase the likelihood of finding false positive associations.
This study will be of interest to neurologists as it supports what other studies have found, a link between education and reduced risk of clinical dementia. It furthers the understanding of how this protection may be occurring by also finding no association between education and brain pathology.