Occupational risk factors in Alzheimers disease: a review assessing the quality of published epidemiological studies

Abstract

Epidemiological evidence of an association between Alzheimers disease AD and the most frequently studied occupational exposurespesticides, solvents, electromagnetic fields EMF, lead and aluminiumis inconsistent. Epidemiological studies published up to June of 2003 were systematically searched through PubMed and Toxline. Twenty-four studies 21 casecontrol and 3 cohort studies were included. Median GQI was 36.6 range 19.562.9. Most of the casecontrol studies had a GQI of <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 arising 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. For the remaining occupational agents, the evidence of association is less consistent for solvents and EMF or absent for lead and aluminium.