Objectives. Epidemiological evidence of the association between Alzheimers disease (AD) and most frequently studied occupational exposures -pesticides, solvents, electromagnetic fields (EMF), lead and aluminium- is inconsistent. The aim of this study is to assess the associations between AD and these exposures based on the evaluation of published studies with a standardised and systematic approach. Methods. Epidemiological studies published up to June of 2003 were systematically searched through PubMed and Toxline. Selected studies were independently evaluated by two blind expert epidemiologists through specific questionnaires. According to scores in the questionnaires a global quality index (GQI) was calculated (percent, range 0-100) for each study. The presence of potential biases was also estimated. Results. Twenty four studies (21 case-control and 3 cohort studies) were included. Median GQI was 36.6% (range 19.5%-62.9%). Most of the case-control studies showed GQI below 50%. The study with the highest score was a cohort study. Likelihood of exposure misclassification bias affected 18 of the 24 studies. Opportunity for bias arose too from the use of surrogate informants affected 17 studies, followed by disease misclassification (11 studies) and selection bias (10 studies). Eleven studies explored the relationship of AD with solvents, seven with EMF, six with pesticides, six with lead and three with aluminium. For pesticides, studies of greater quality and prospective design found increased and statistically significant associations. Regarding the remaining occupational agents, the evidence of association is less consistent (for solvents and EMF) or absent (for lead and aluminium). Conclusions. According to our assessment, quality of epidemiological studies on Alzheimers disease and occupational exposures is generally low, with high probability for bias. Considering only higher quality studies, pesticides are the agents for which there is greater evidence of association with the disease.
- Alzheimer disease
- electromagnetic fields
- occupational exposure
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