Association of microplastics in human cerebrospinal fluid with Alzheimer's disease-related changes

To investigate potential associations between cerebrospinal fluid (CSF) microplastics and Alzheimer's disease (AD) pathology or cognitive function. The study included two cohorts: Cohort 1 comprised 17 amyloid-positive and 15 amyloid-negative subjects, while Cohort 2 consisted of 11 amyloid-positive subjects. All amyloid-positive participants in Cohort 1 completed one-year follow-up. CSF amyloid-β(Aβ)42, Aβ40, p-tau181, and t-tau were measured. Amyloid status defined by CSF Aβ42/40 ratio (positive: < 0.1; negative: ≥ 0.1). Four types of microplastics, namely polypropylene, polyvinyl chloride (PVC), polyethylene (PE), and polystyrene, were detected in human CSF. Bottled water consumption frequency and CSF/serum albumin ratio significantly correlated with CSF microplastic abundance. In Cohort 1, amyloid-positive subjects exhibited significantly elevated CSF levels of PE and PVC as compared to amyloid-negative subjects. In amyloid-positive subjects (Cohort 1 and 2), CSF PE levels showed significant inverse correlations with both CSF Aβ42 levels and Mini-Mental State Examination (MMSE) scores. In amyloid-positive individuals of Cohort 1, elevated PE levels positively correlated with MMSE decline rate over one year. The levels of CSF Aβ42 served as an intermediary factor, significantly affecting the relationship between CSF PE and MMSE scores in amyloid-positive subjects of cohort 1. In Cohort 1, the CSF levels of PE and PVC demonstrated an area under the curve value of greater than 0.8, indicating their strong potential to differentiate between amyloid-positive and amyloid-negative individuals. These discoveries suggested that the gradual accumulation of microplastics in the CSF were associated with cognitive decline among AD individuals.