Environmental noise exposure and a new biomarker of Alzheimer's disease: A pilot study.

BackgroundEnvironmental noise pollution is increasingly recognized as a contributor to neurodegenerative processes, yet its relationship with early Alzheimer's disease biomarkers remains unclear.ObjectiveThis pilot study aimed to assess the feasibility of using gray-to-white matter signal intensity contrast (GWC) as a potential biomarker to explore associations between environmental noise exposure and early neurodegenerative changes.MethodsA total of 106 participants (mean age 35.97 ± 9.21 years, range 20-55), without cognitive impairment or neurological disorders, were included. Environmental noise levels were estimated using spatial interpolation from the National Noise Information System. Based on WHO guidelines (>60 dB daytime or >55 dB nighttime), participants were categorized into high- and low-noise groups. Whole-brain and regional GWC values were derived from 3D T1-weighted MRI using FreeSurfer. Correlations between noise exposure and GWC were analyzed with Pearson's correlation.ResultsThe high-noise group exhibited elevated whole-brain GWC values (20.11 ± 0.93) compared with the low-noise group (19.68 ± 0.96; p = 0.036). Regional analyses revealed higher GWC in the superior frontal gyrus, precentral gyrus, and paracentral lobules (all p < 0.05, FDR corrected). Nighttime noise exposure correlated more strongly with increased GWC (r = 0.203, p = 0.037) than daytime exposure.ConclusionsThis pilot study provides preliminary evidence of an association between environmental noise-particularly nighttime exposure-and subtle structural brain changes, as indicated by elevated GWC values. These findings suggest a potential neurobiological pathway linking noise exposure to early markers of neurodegeneration, warranting validation in larger, longitudinal studies.