Toxic Environmental Risk Factors for Alzheimer\u27s Disease: A Systematic Review

There is growing evidence of a possible association between toxic environmental factors and Alzheimer’s disease (AD), a disabling neurodegenerative condition with no known cause. Previous reviews of toxic environmental factors for AD either focused on occupational exposures or used a non-systematic methodology. The objective of this systematic review is to assess the evidence on the link between AD and exposure to a variety of toxic environmental risk factors beyond the work environment. Structured database search was used to identify relevant studies. Twenty-nine eligible studies examining the effect of various toxic environmental agents including electromagnetic fields, solvents, pesticides, toxic metals, and air pollutants were identified. Six out of 11 cohort studies and only two out of 18 case-control studies were considered high quality. Eight out of 12 studies found electromagnetic fields exposure to be a significant risk factor for AD. Significant evidence was also found for pesticide, aluminum, and solvent exposures. Evidence is now emerging of a possible association between air pollution and AD. However, more research is needed to substantiate this evidence. Key methodological issues especially those relating to the assessment of exposure(s) need to be addressed in future studies to facilitate interpretation and synthesis of study result