BACKGROUND: The pathogenesis of amyotrophic lateral sclerosis (ALS) involves both environmental and genetic factors. Our study aimed at summarising the environmental risk factors for ALS, assessing the evidence for diverse biases, and pinpointing risk factors with high epidemiological credibility. METHODS: We searched PubMed from inception to August 20, 2015, to identify systematic reviews and meta-analyses of observational studies examining associations between environmental factors and ALS. For each meta-analysis, we estimated the summary effect size by the use of random-effects and fixed-effects models, the 95% CI, the 95% prediction interval (PI), and the between-study heterogeneity. We assessed the evidence of small-study effects and excess significance bias. RESULTS: Sixteen unique meta-analyses of different risk factors and ALS were considered. Of them, 5 were statistically significant at p < 0.001 under the random-effects model. Only one factor presented robust evidence for a convincing association. This association pertained to chronic occupational exposure to lead (random-effects OR 1.81, 95% CI 1.39-2.35). CONCLUSIONS: A small number of published meta-analyses on environmental factors and risk of ALS was identified, a phenomenon that could be attributed to the challenges in studying a rare neurological disease. More observational studies with adequate sample size and study design are needed to clarify the environmental component of ALS pathogenesis.
BACKGROUND: The pathogenesis of amyotrophic lateral sclerosis (ALS) involves both environmental and genetic factors. Our study aimed at summarising the environmental risk factors for ALS, assessing the evidence for diverse biases, and pinpointing risk factors with high epidemiological credibility. METHODS: We searched PubMed from inception to August 20, 2015, to identify systematic reviews and meta-analyses of observational studies examining associations between environmental factors and ALS. For each meta-analysis, we estimated the summary effect size by the use of random-effects and fixed-effects models, the 95% CI, the 95% prediction interval (PI), and the between-study heterogeneity. We assessed the evidence of small-study effects and excess significance bias. RESULTS: Sixteen unique meta-analyses of different risk factors and ALS were considered. Of them, 5 were statistically significant at p < 0.001 under the random-effects model. Only one factor presented robust evidence for a convincing association. This association pertained to chronic occupational exposure to lead (random-effects OR 1.81, 95% CI 1.39-2.35). CONCLUSIONS: A small number of published meta-analyses on environmental factors and risk of ALS was identified, a phenomenon that could be attributed to the challenges in studying a rare neurological disease. More observational studies with adequate sample size and study design are needed to clarify the environmental component of ALS pathogenesis.
Authors: Joaquim Radua; Valentina Ramella-Cravaro; John P A Ioannidis; Abraham Reichenberg; Nacharin Phiphopthatsanee; Taha Amir; Hyi Yenn Thoo; Dominic Oliver; Cathy Davies; Craig Morgan; Philip McGuire; Robin M Murray; Paolo Fusar-Poli Journal: World Psychiatry Date: 2018-02 Impact factor: 49.548
Authors: Angeline S Andrew; Tracie A Caller; Rup Tandan; Eric J Duell; Patricia L Henegan; Nicholas C Field; Walter G Bradley; Elijah W Stommel Journal: Neurodegener Dis Date: 2017-01-26 Impact factor: 2.977
Authors: Anna Freydenzon; Marta F Nabais; Tian Lin; Kelly L Williams; Leanne Wallace; Anjali K Henders; Ian P Blair; Naomi R Wray; Roger Pamphlett; Allan F McRae Journal: Sci Rep Date: 2022-06-22 Impact factor: 4.996
Authors: Perrine Janiaud; Arnav Agarwal; Ioanna Tzoulaki; Evropi Theodoratou; Konstantinos K Tsilidis; Evangelos Evangelou; John P A Ioannidis Journal: BMC Med Date: 2021-07-06 Impact factor: 11.150