Causality between noise pollution and Alzheimer disease: A Mendelian randomization analysis

Area of Science:

• Neuroscience
• Environmental Health
• Genetics

Background:

• Observational studies on noise pollution and Alzheimer disease (AD) risk present conflicting results.
• Confounding factors and reverse causality limit the interpretation of existing observational data.
• Clarifying the direct causal relationship between noise exposure and AD is crucial for public health.

Purpose of the Study:

• To investigate the potential causal effect of noise pollution on Alzheimer disease (AD) risk.
• To address limitations of previous observational studies using a robust genetic epidemiology approach.
• To differentiate direct causal links from indirect associations in the noise-AD relationship.

Main Methods:

• A 2-sample Mendelian randomization (MR) study was conducted using large-scale genome-wide association study summary statistics.
• Genetically predicted daytime and evening noise exposure served as instrumental variables for AD risk.
• Inverse-variance weighted methods were employed, with weighted median and MR-Egger as sensitivity analyses.

Main Results:

• No evidence of a causal association was found between genetically predicted daytime noise exposure and AD risk (OR u2005= u20050.999 [0.993-1.006], P u2005= u2005.819).
• Similarly, no causal link was observed for evening noise exposure and AD risk (OR u2005= u20050.999 [0.993-1.005], P u2005= u2005.643).
• Sensitivity analyses confirmed the absence of heterogeneity and directional pleiotropy, supporting the primary findings.

Conclusions:

• This Mendelian randomization study does not support a direct causal relationship between noise pollution and Alzheimer disease.
• The findings suggest that observed associations in observational studies may be influenced by indirect pathways.
• Future research should focus on elucidating indirect mechanisms, such as chronic sleep disruption and cardiovascular stress, linking noise exposure to AD pathogenesis.