title: Systematic reviews of factors associated with the onset and progression of neurological conditions in humans: A methodological overview.
abstract: As a component of the National Population Health Study of Neurological conditions, systematic reviews were conducted to identify risk factors associated with the onset and progression of 14 priority neurological conditions. Between 2011 and 2013, electronic databases and grey literature sources were searched to identify systematic reviews and primary studies reporting on the onset and progression of each condition. Inclusion was restricted to studies of humans reported in English or French. Additional condition-specific eligibility criteria were also applied. Titles and abstracts were screened by one reviewer with excluded records verified by a second reviewer. Full-text reports were screened independently by two reviewers. Disagreements were resolved by consensus or third party adjudication. Systematic reviews were quality appraised using the AMSTAR criteria, with only moderate and high quality reviews considered for inclusion. Primary studies were also sought to ensure that evidence from existing systematic reviews was supplemented with recent primary study findings (i.e., those published after the most recent systematic review). Evidence from primary studies was also considered if a systematic review was unavailable or of poor quality. Data were extracted using standardized forms. Where feasible, data were extracted independently by two reviewers. Otherwise, data were extracted by a single reviewer and independent data extraction by a second reviewer was conducted for a randomly selected sample of studies. An updated search was conducted in 2016 to identify systematic reviews published since the initial search in 2011-2013. A summary of the methodology used to conduct the systematic reviews is described. Illustrative results are provided for the risk of amyotrophic lateral sclerosis in relation to occupational exposure to lead and other heavy metals.
authors.affiliation: McLaughlin Centre for Population Health Risk Assessment, University of Ottawa, Ottawa, ON, Canada; School of Epidemiology, Public Health and Preventive Medicine, Faculty of Medicine, University of Ottawa, Ottawa, ON, Canada.
authors.forename: Mona
authors.initials: M
authors.lastname: Hersi
authors.affiliation: McLaughlin Centre for Population Health Risk Assessment, University of Ottawa, Ottawa, ON, Canada; School of Epidemiology, Public Health and Preventive Medicine, Faculty of Medicine, University of Ottawa, Ottawa, ON, Canada.
authors.forename: Pauline
authors.initials: P
authors.lastname: Quach
authors.affiliation: School of Epidemiology, Public Health and Preventive Medicine, Faculty of Medicine, University of Ottawa, Ottawa, ON, Canada; School of Life Science, Changchun Normal University, Changchun, Jilin 130032, China.
authors.forename: Ming-Dong
authors.initials: MD
authors.lastname: Wang
authors.affiliation: McLaughlin Centre for Population Health Risk Assessment, University of Ottawa, Ottawa, ON, Canada; Interdisciplinary School of Health Sciences, Faculty of Health Sciences, University of Ottawa, ON, Canada; Environmental Health Research Unit, University of Ottawa, ON, Canada.
authors.forename: James
authors.initials: J
authors.lastname: Gomes
authors.affiliation: School of Epidemiology, Public Health and Preventive Medicine, Faculty of Medicine, University of Ottawa, Ottawa, ON, Canada.
authors.forename: Janet
authors.initials: J
authors.lastname: Gaskin
authors.affiliation: McLaughlin Centre for Population Health Risk Assessment, University of Ottawa, Ottawa, ON, Canada; School of Epidemiology, Public Health and Preventive Medicine, Faculty of Medicine, University of Ottawa, Ottawa, ON, Canada; Risk Sciences International, Ottawa, ON, Canada.
authors.forename: Daniel
authors.initials: D
authors.lastname: Krewski
mesh_terms: D016206:Databases, Bibliographic / Q000706:statistics & numerical data; D018450:Disease Progression; D006801:Humans; D015201:Meta-Analysis as Topic; D009422:Nervous System Diseases / Q000453:epidemiology* / Q000209:etiology*; D012307:Risk Factors
keywords: AMSTAR; Data extraction; Meta-analyses; Neurological disease; Risk factors; Systematic review