“Tiny clots in the brain may be the cause of some signs of old age such as stooped posture and restricted movement,” reports the BBC.
This story is based on a study that assessed movement problems in older people and then carried out an in-depth examination of their brains after death to look for any small areas of brain damage. It found that there was a relationship between small areas of brain tissue death (possibly due to small blood clots) and the level of movement problems a person had.
Importantly, this study only looked at people’s brains after they died. This means it is not possible to be certain that these changes occurred before the person’s problems with movement began and not afterwards. This means we cannot be certain that these brain changes caused the movement problems in older people. Further studies using brain imaging during a person’s life, followed by examination of their brain after death might help clarify the link further. However, some of the changes would not be detectable with the currently available brain imaging techniques.
For now, this association should be considered to be a tentative one, until further research in larger numbers of brains can be carried out.
Where did the story come from?
The study was carried out by researchers from Rush University Medical Center in Chicago. Funding was provided by grants from the National Institutes of Health and the Illinois Department of Public Health. The study was published in the peer-reviewed medical journal Stroke.
The BBC provides good coverage of this story.
What kind of research was this?
This was a cross sectional analysis in which researchers looked at brain autopsies to see whether any changes in the brain were related to the movement problems experienced by older people.
The researchers were particularly interested in a group of problems called “parkinsonian signs”, which are commonly seen in older people. These include slowing of movement, problems with posture and walking stride, as well as tremor and rigidity (stiffness). They are called parkinsonian signs because they are similar to the problems seen in Parkinson’s disease, but their presence does not necessarily mean that an older person has this disease. Older people without any known nervous system or brain problems often develop mild parkinsonian signs.
The researchers wanted to see whether there were any brain changes that might account for these signs, by carrying out a detailed look at the brains of older people after they died and relating this to any parkinsonian signs they showed while alive.
This method can identify links between brain changes and level of parkinsonian symptoms, but cannot say for certain that these brain changes caused the signs.
What did the research involve?
The researchers used participants from an ongoing cohort study called the Religious Order Study, who had agreed to allow their brains to be dissected after they died. The participants had had their level of parkinsonian signs assessed while they were alive, and after they died the researchers looked at their brains. They then looked at whether there was a relationship between level of parkinsonian signs and any brain changes seen.
The Religious Order Study is a study primarily aimed at investigating potential causes of dementia and cognitive impairment. The study recruited older members of the religious clergy who had not been diagnosed with dementia when they enrolled. The participants were assessed every year. This included an assessment measuring their levels of parkinsonian signs. This assessment provided an overall parkinsonian sign score, as well as individual scores for walking stride (gait), slowness of movement, rigidity and tremor.
At the time of the study write up, 418 people had died (average age 88.5 years) and had their brains examined. Almost half (45%) had dementia. The researchers examined the brain tissue for small areas where the brain tissue had died, called infarcts. These occur when blood clots block a small blood vessel in the brain cutting off blood supply to a small area of the brain. If the infarct is large enough, a person would be said to have had a stroke. They also looked for thickening of the walls of the small blood vessels in the brain that could lead to blockages.
The researchers then looked at whether there was a relationship between a person’s level of parkinsonian signs at the last assessment before they died and the level of brain changes seen. The researchers took into account a person’s age and gender, level of education, whether their brain showed signs of Parkinson’s disease, body mass index, depressive symptoms and the presence of seven chronic conditions including stroke and head injury. The analyses also took into account the presence of each of the other types of brain changes assessed.
Because both infarcts and parkinsonian signs are associated with an increased risk of dementia, the researchers also tested the data to see if the association could be explained by the presence of dementia.
What were the basic results?
The researchers found that problems with walking stride were the most common parkinsonian sign. The overall level of parkinsonian signs was higher in those people who also had dementia.
On post-mortem, almost 36% of participants had areas of brain tissue death that were visible to the naked eye. An additional 29% did not have these larger, more visible areas of damage, but did have areas of brain tissue death visible under the microscope, or thickening of the walls of the small blood vessels in the brain. These smaller changes would not be visible with the conventional brain imaging techniques that can be used while a person is alive.
People with areas of brain tissue death visible to the naked eye were more likely to have had higher levels of parkinsonian signs in life. This relationship was strongest in people with three or more areas of brain tissue death visible to the naked eye. Whether or not a person had dementia did not affect this relationship.
The relationship between small areas of brain damage only visible under the microscope and level of parkinsonian signs was only statistically significant in people with more than one such area of damage. There was no significant relationship between the thickening of the walls of the small blood vessels in the brain and level of parkinsonian signs.
Each of the three different types of brain changes was related to changes in walking stride (gait). These relationships did not differ in those with or without dementia.
How did the researchers interpret the results?
The researchers concluded that the types of brain changes they looked at are common in older people. They say that these changes may be previously unrecognised common causes of mild parkinsonian signs in older age, particularly changes in walking stride. If this is the case, then they say that these problems might be alleviated by more prevention and treatment of risk factors for this sort of damage (blood clots and blood vessel narrowing).
This research suggests that the changes in people’s movements seen as they get older may be related to small areas of damage in the brain. Importantly, as this study only looked at people’s brains after they died it is not possible to be certain that these changes did occur before they started having problems with movement and not afterwards. This means we cannot be certain that these brain changes caused the movement problems in older people.
The researchers suggest that studies using brain imaging during a person’s life, followed by examination of their brain after death might help clarify the link further. However, some of the changes would not be detectable with the currently available brain imaging techniques. The researchers also say that their findings should be confirmed in larger numbers of brains.
For now this association between small brain changes and the movement problems associated with ageing remains tentative.
- Buchman AS, Leurgans SE, Nag S, et al. Cerebrovascular disease pathology and Parkinsonian signs in old age. Stroke Sept 2011. Advance online publication.