Blockages in tiny blood vessels in the brain that can’t be detected with modern technology could be responsible for many of the “parkinsonian” signs of aging, such as stooped posture, difficulty balancing, slowed walking and shaky hands, according to a study from Rush University Medical Center in Chicago, USA, reported online in the 1 September issue of Stroke: Journal of the American Heart Association. The researchers said we should not accept parkinsonian signs as a normal part of aging, but should understand what causes them and try to treat them.
Lead author of the study, Dr. Aron S. Buchman, an associate professor of neurological sciences at Rush, said they were very surprised by their findings:
“The public health implications are significant because we are not identifying the 30 percent who have undiagnosed small vessel disease that is not picked up by current technology. We need additional tools in order to identify this population,” he told the press.
Although only about 5% of older people develop Parkison’s disease, mild motor symptoms, including those also seen in Parkinson’s disease, increase with age, so that half of people have them by the time they reach the age of 85, write Buchman and colleagues in their background information.
Yet, despite this high prevalence, we don’t know much about the underlying causes in the brain, so they decided to investigate the idea that blood vessel problems could be a factor.
They studied brain autopsies from dead people who were taking part in the Religious Order Study. This study started in 1994, when researchers began carrying out annual exams looking for signs of aging in 1,100 older nuns and priests who had also consented for their brains to be examined when they died.
The annual exams included evaluation for parkinsonian signs via a modified version of the motor section of the Unified Parkinson’s Disease Rating Scale which assesses things like balance, ability to maintain posture, walking speed, sense of diziness, ability to turn a corner while walking, and ability to get in and out of a chair.
This study reports the results from the first 418 brain autopsies. The participants were on average 88 years old when they died, and 61% of them were women.
The researchers examined the brains for infarcts, areas of brain tissue that have died off because of a blockage in the blood supply. They looked for macroscopic and microinfarcts, that is blockages in large and tiny blood vessels, and they also measured the severity of arteriolosclerosis, or the amount of thickening in the walls of the blood vessels.
Using a statistical method called regression analysis they looked for links between the brain autopsy data and the parkinsonian signs evaluations that the participants had completed in the years up to their death.
The results showed that:
- More than 149 participants (35%) had signs of macroscopic infarcts in their brains.
- In nearly 30% of those who did not show signs of macroscopic infarcts, and who had had no diagnosis of brain disease or stroke during their lives, there was evidence of damage that would not be detected by conventional brain imaging.
- Of these, 33 individuals (7.9%) had microinfarcts, 62 (14.8%) had arteriolosclerosis, while 24 (5.7%) had both.
- Macroscopic infarcts were linked to higher global parkinsonian scores,and while arteriolosclerosis was linked to global parkinsonian score, this effect reduced and became no longer significant after the effect of infarcts was taken out.
- Each of the three types of damage (macroscopic infarct, microscopic infarct, arteriosclerosis) was separately linked with parkinsonian gait.
- Further analysis showed that “subcortical macroscopic and microinfarcts were specifically associated with the severity of parkinsonian gait”.
Parkinsonian gait is a sign of Parkinson’s disease characterized by a number of features to do with the way a person walks, including leaning forward and stooping, and taking small, shuffling steps.
This study shows that the individuals who had the most trouble walking, had multiple undetectable brain lesions.
Buchman and colleagues concluded that:
“Cerebrovascular pathologies, including macroscopic infarcts, microinfarcts, and arteriolosclerosis, are common in older persons and may be unrecognized common etiologies of mild parkinsonian signs, especially parkinsonian gait, in old age.”
Buchman, who is also a member of the Rush Alzheimer’s Disease Center, said:
“Often the mild motor symptoms are considered an expected part of aging,” however he added “we should not accept this as normal aging,” but instead, should try to understand it and fix it.
“If there is an underlying cause, we can intervene and perhaps lessen the impact,” said Buchman.
Written by Catharine Paddock PhD