We do not have a clear picture of cause and effect, but microplastics and nanoplastics were found in high concentrations in autopsied brains of patients with dementia.

Visible macroplastics, such as bottles and bags, litter our environment and ultimately break down into invisible microplastics and nanoplastics (MNPs). Levels of MNPs in the environment have been rising exponentially during the past two decades. In 2024, researchers reported that MNPs were present in carotid atheromas with increased inflammation and that this was associated with future risk for adverse cardiovascular events (N Engl J Med 2024; 390: 900-910).

Using mass spectroscopy and electron microscopy to detect the smallest nanoplastics, a team from New Mexico examined autopsy specimens from multiple organs in 2016 and again in 2024. They report the following:

• concentrations of MNPs in multiple organs increased substantially from 2016 to 2024
• concentrations in the brain were seven to 30 times higher than in other organs, including liver and kidneys
• brain samples from people with dementia had higher concentrations of MNPs than did the brains of people without dementia.

Comment: For me, the most striking finding of this study is the rapid rise in the concentration of MNPs in human autopsy tissues in just the eight years between 2016 and 2024. It is time to intensify study of potential health threats associated with MNPs. Higher concentrations of MNPs in people with dementia could reflect a causal role for MNPs, but it could just as easily be a consequence of the pathology of dementia – particularly impairment of both blood-brain barrier integrity and glymphatic clearance of toxins from the brain.

Anthony L. Komaroff, MD, Professor of Medicine, Harvard Medical School, Boston, USA.

Nihart AJ, et al. Bioaccumulation of microplastics in decedent human brains. Nat Med 2025 Feb 3; e-pub (https://doi.org/10.1038/s41591-024-03453-1).

This summary is taken from the following Journal Watch titles: General Medicine, Neurology.