â€œThe 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,â€ he told the press.
Although only about 5% of older people develop Parkisonâ€™s disease, mild motor symptoms, including those also seen in Parkinsonâ€™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 donâ€™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 Parkinsonâ€™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 â€œsubcortical macroscopic and microinfarcts were specifically associated with the severity of parkinsonian gaitâ€.
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