Air pollution speeds up Parkinson’s via the gut
Air pollution raises the risk of Parkinson’s disease. But the mechanism doesn’t run only through the lungs. A new analysis points to the gut as a key intermediary.
Fine particles and other air pollutants have long been linked to neurodegenerative diseases. Less well known is how that connection works. The researchers describe several routes in their review article, of which the gut is a striking one.
It starts in the gut
In Parkinson’s disease, a clumped protein plays a central role: alpha-synuclein. This protein can appear in the gut’s nervous system years before the first brain symptoms. It then spreads to the brain via the vagus nerve, the large nerve connecting gut and brain.
Exposure to air pollution disrupts the composition of the gut microbiome (the community of bacteria in your intestines). Bacteria that produce short-chain fatty acids, substances that suppress inflammation, decrease in number. At the same time, the permeability of the gut wall increases. This promotes inflammation throughout the body, including in the brain.
Inflammation as an accelerator
The broader effect of air pollution largely operates via chronic low-grade inflammation (inflammaging): a persistent, mild activation of the immune system that increases with age. Fine particles and nitrogen oxides irritate cells in the airways, which then release inflammatory signals that reach the entire body. These signals accelerate the accumulation of alpha-synuclein in the brain, supporting the progression of Parkinson’s disease.
Studies in the Puget Sound region showed that higher exposure to air pollution also raises dementia risk. The magnitude of this effect varies by region: areas where wood and coal are used for heating and cooking have higher particulate concentrations, and therefore higher risks. But measurable effects have also been demonstrated in wealthier countries.
This is a review study summarizing existing research. Causal links in humans have not yet been fully established. For those concerned about brain health in later life, reducing exposure to fine particulate matter is a starting point that enjoys broad scientific support.
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