8287737 Occupational exposure to pesticides increases the risk of amyotrophic lateral sclerosis: a meta-analysis

<h3>Objective</h3> To assess the strength of evidence on the association between occupational exposure to pesticides and the risk of amyotrophic lateral sclerosis (ALS). <h3>Material and Methods</h3> A systematic literature search was conducted in nine bibliographic databases for articles published between January 1980 and August 2023. Eligible articles reported on observational studies that presented specific risk estimates for ALS in relation to occupational exposure to pesticides. Evaluation of the quality of studies was carried out using the WHO Risk of bias (RoB) assessment instrument for systematic reviews with the ROBINS-E domains of bias. Adjusted risk estimates were pooled with random-effect models, heterogeneity was assessed using the I² statistic, and publication bias, using funnel plots and Egger’s test. <h3>Results</h3> One cohort and eight case-control studies, published between 1997 and 2022 representing a total of 2600 ALS cases, were retained as relevant for meta-analysis, out of 140 initially identified articles. Ever occupational exposure to pesticides was associated with an increased risk of ALS (n=7 studies, odds ratio [OR]=1.5, 95% confidence interval [CI] 1.1-2.1; I²=60%), for all sex combined. With estimates stratified by type of pesticides, the overall OR was 1.3 (n=6, 95%CI 1.0-1.7; I²=13%), with herbicides and insecticides being associated with higher risks (both ORs=1.4) than fungicides (OR=1.2). The exclusion of the cohort study only marginally increased these risk estimates. Ever exposure to high levels of pesticides was associated with a larger risk than exposure to low levels (n=3, OR=2.7, 1.4-5.0 vs. OR=1.9, 1.0-3.7, I2=0%). There was no obvious funnel plot asymmetry and the heterogeneity between studies appeared to be due to differences in study population and the variety of exposure assessment methods. <h3>Conclusion</h3> Despite inconsistencies between certain results, and remaining problems with the quality of exposure assessment, the available evidence suggests that occupational exposure to pesticides may increase the risk of SLA.