Rural environment, pesticide exposure and the risk of amyotrophic lateral sclerosis: a meta analysis

Abstract

Objective To explore the relationship between the risk of amyotrophic lateral sclerosis (ALS) and exposure to rural environments and pesticide. Methods Studies relevant to rural residence, farmer occupation, pesticide exposure and ALS were identified from the databases including Embase, Ovid Medline, Pubmed, Cochrane Library, Wanfang data, Chinese BioMedical Literature Database, Chinese National Knowledge Infrastructure, China Science and Technology Journal Database up to March 2015.Quality of studies was assessed according to the Newcastle-Ottawa Scale (NOS). Analysis of data and publication bias was performed with software Revman 5.3. Results A total of 24 case-control studies and 3 cohort studies were included into the analysis.The NOS scores of all studies were ≥6. The risk of ALS was associated with pesticide exposure (OR=1.41, 95% CI 1.28-1.56) and farmer occupation (OR=1.42, 95% CI 1.29-1.57), but not associated with rural residence (OR=1.21, 95% CI 0.97-1.51). Subgroup analysis of pesticide exposure and ALS revealed that males (OR=1.75, 95% CI 1.39-2.21) had a higher risk than females (OR=1.53, 95% CI 1.13-2.08), and the risk estimate was higher in studies using El Escorial standard (OR=1.68, 95% CI 1.45-1.95) than studies not (OR=1.23, 95% CI 1.08-1.40). The meta analysis had a slight publication bias. Conclusions Our findings support pesticide exposure might increase the risk of ALS. Given that farmers always have high levels of pesticide exposure in their work, they should decrease their exposure level or take proper precautions to lower the risk of ALS. Key words: Amyotrophic lateral sclerosis; Pesticide residues; Risk factors; Environmental exposure; Meta-analysis