A novel risk factor for dementia: chronic microplastic exposure.

Abstract

Recent advances in dementia research have expanded our understanding of modifiable risk factors, with air pollution being a well-established contributor. However, microplastics-plastic particles smaller than 5 mm-represent an understudied component of environmental pollution that may significantly impact neurological health. This review examines emerging evidence linking chronic microplastic exposure to increased dementia risk. Microplastics enter the human body through multiple routes, including ingestion of contaminated food and water, inhalation, and dermal absorption, with demonstrated ability to cross the blood-brain barrier and initiate several pathogenic pathways. Four primary mechanisms appear to mediate microplastic-induced neurodegeneration: increased oxidative stress through reactive oxygen species (ROS) production; neuroinflammation via microglial activation and chronic inflammatory responses; neurotoxicity from transported persistent organic pollutants (POPs) and heavy metals; and accelerated amyloid-beta pathology through enhanced Aβ40 and Aβ42 nucleation. Recent bioaccumulation studies have revealed significantly elevated microplastic concentrations in the brains of dementia patients compared to non-dementia controls, supporting a potential dose-dependent relationship. Sources of environmental microplastics include industrial waste, synthetic textiles, plastic degradation products, and tire wear particles, creating a ubiquitous exposure risk through contaminated air, food, and water. While preliminary evidence supports a mechanistic link between microplastics and neurodegeneration, comprehensive epidemiological studies with larger datasets are needed to quantify this relationship and establish dose-response patterns. Future research should focus on identifying which microplastic types pose the greatest neurological risks, determining threshold exposure levels, and developing interventions to mitigate exposure.