Loud sound exposure & its connection to deadly disease
In this DML Report…
A recent study published in the journal PLOS Biology by researchers in China examined the impact of loud noise exposure on early-stage Parkinson's disease using genetically modified mice that modeled the condition without initial symptoms. The mice were placed in soundproof chambers and exposed to noise levels between 85 and 100 decibels, equivalent to the sound of a lawn mower or blender, delivered in random bursts of 5 to 30 seconds at varying intensities. In one experiment, a single one-hour exposure caused immediate slower movement and reduced balance, with recovery occurring the next day. In another, daily one-hour exposures over seven days resulted in chronic movement difficulties and persistent motor deficits.
The research identified a neural connection between the inferior colliculus, a brainstem region that processes sound, and the substantia nigra pars compacta, where dopamine-producing cells are located and often damaged in Parkinson's. Chronic noise exposure activated the inferior colliculus, reducing levels of vesicular monoamine transporter 2 (VMAT2), a protein essential for transporting neurotransmitters like dopamine into neurons, which led to the death of these dopamine cells and subsequent balance issues. Inhibiting the inferior colliculus increased VMAT2 production and reversed the noise-induced harm. The authors noted that this demonstrates how environmental noise can trigger dopaminergic neurodegeneration and motor deficits, providing insights into non-genetic risk factors for Parkinson's progression.
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Parkinson's disease, a progressive neurological disorder affecting about 1 million Americans with projections of 1.2 million cases by 2030, involves the loss of dopamine-producing nerve cells, leading to symptoms such as tremors, stiffness, balance problems, and speech difficulties, with around 90,000 new diagnoses and 35,000 deaths annually in the U.S.—a 50 percent rise from prior estimates. Experts attribute part of the increase to environmental factors, including a 36 percent higher risk from exposure to PM2.5 pollutants as found in a Minnesota study, and links to consuming at least 11 servings of ultra-processed foods daily, which may damage dopamine neurons. While there is no cure, treatments like Levodopa can cross the blood-brain barrier to replace lost dopamine and manage symptoms.