The brain is like a house built too spacious: it's pleasant to live in, but expensive to maintain. Parkinson's disease is usually associated with the brain shrinking and breaking down. But a new study has shown that in people whose genes raise the risk of this disease, the brain is larger from the very start, not smaller.
Researchers examined data from 46,349 healthy people. For each one they calculated a polygenic risk score (the combined contribution of many genetic variants) and measured the brain using MRI. It turned out that people at high risk have a larger cortical surface area, a larger volume of subcortical nuclei, and better-organized white matter fibers. The same features were found in children aged 10-16, which means they appear long before the disease.
Genes that make the brain grow more strongly are more active even before birth. They are responsible for cell division and building the scaffold of neurons. It follows that vulnerability to Parkinson's disease is established in early development, not in old age. For now this knowledge doesn't offer treatments, but it helps explain why some people get sick and others don't.
Polygenic Parkinson's disease risk turned out to be linked to higher levels of education, income, and even less smoking, that is, to traits usually considered protective for brain health.
Not published on arXiv. Here are its page, the PDF and the formalization: you can check it yourself, not only read our account.