title: Overview of systematic reviews in allergy epidemiology.
abstract: BACKGROUND
  There is a substantial body of evidence on the epidemiology of allergic conditions, which has advanced the understanding of these conditions. We aimed to systematically identify systematic reviews and meta-analyses on the epidemiology of allergic diseases to assess what has been studied comprehensively and what areas might benefit from further research.
  
  
  METHODS
  We searched PubMed and EMBASE up to 12/2014 for systematic reviews on epidemiological research on allergic diseases. We indexed diseases and topics covered and extracted data on the search characteristics of each systematic review.
  
  
  RESULTS
  The search resulted in 3991 entries after removing duplicates, plus 20 other items found via references and conference abstracts; 421 systematic reviews were relevant and included in this overview. The majority contained some evidence on asthma (72.9%). Allergic rhinitis, atopic eczema and food hypersensitivity were covered in 15.7%, 24.5% and 9.0%, respectively. Commonly studied risk factors for atopic eczema included dietary and microbial factors, while for asthma, pollution and genetic factors were often investigated in systematic reviews. There was some indication of differing search characteristics across topics.
  
  
  CONCLUSIONS
  We present a comprehensive overview with an indexed database of published systematic reviews in allergy epidemiology. We believe that this clarifies where most research interest has focussed and which areas could benefit from further research. We propose that this effort is updated every few years to include the most recently published evidence and to extend the search to an even broader list of hypersensitivity/allergic disorders.
authors.affiliation: Institute of Epidemiology and Medical Biometry, Ulm University, Ulm, Germany.
authors.forename: J
authors.identifier: http://orcid.org/0000-0001-5764-1528
authors.initials: J
authors.lastname: Genuneit
authors.affiliation: Institute of Epidemiology and Medical Biometry, Ulm University, Ulm, Germany.
authors.forename: A M
authors.initials: AM
authors.lastname: Seibold
authors.affiliation: Institute of Epidemiology and Preventive Medicine, University of Regensburg, Regensburg, Germany.
authors.forename: C J
authors.identifier: http://orcid.org/0000-0003-3805-8219
authors.initials: CJ
authors.lastname: Apfelbacher
authors.affiliation: Department of Allergy and Clinical Immunology, 424 General Military Training Hospital, Thessaloniki, Greece.
authors.forename: G N
authors.initials: GN
authors.lastname: Konstantinou
authors.affiliation: Murdoch Children's Research Institute, University of Melbourne, Melbourne, VIC, Australia.
authors.forename: J J
authors.initials: JJ
authors.lastname: Koplin
authors.affiliation: National Research Council of Italy, Institute of Biomedicine and Molecular Immunology, Palermo, Italy.
authors.forename: S
authors.initials: S
authors.lastname: La Grutta
authors.affiliation: Children's Allergies Department, Division of Asthma, Allergy and Lung Biology, King's College London, London, UK.
authors.forename: K
authors.initials: K
authors.lastname: Logan
authors.affiliation: Population Health Research Institute, St George's, University of London, London, UK.
authors.forename: M R
authors.initials: MR
authors.lastname: Perkin
authors.affiliation: Unit for Population-Based Dermatology Research, St John's Institute of Dermatology, King's College London and Guy's and St Thomas' NHS Foundation, London, UK.
authors.forename: C
authors.initials: C
authors.lastname: Flohr
mesh_terms: D001249:Asthma / Q000453:epidemiology; D003876:Dermatitis, Atopic / Q000453:epidemiology; D005512:Food Hypersensitivity / Q000453:epidemiology; D006801:Humans; D006967:Hypersensitivity / Q000453:epidemiology*; D012196:Review Literature as Topic; D065631:Rhinitis, Allergic / Q000453:epidemiology
keywords: allergic diseases; epidemiology; meta-analyses; systematic reviews