title: Systematic review and meta-analysis of prevalence studies in transsexualism.
abstract: BACKGROUND
  Over the last 50 years, several studies have provided estimates of the prevalence of transsexualism. The variation in reported prevalence is considerable and may be explained by factors such as the methodology and diagnostic classification used and the year and country in which the studies took place. Taking these into consideration, this study aimed to critically and systematically review the available literature measuring the prevalence of transsexualism as well as performing a meta-analysis using the available data.
  
  
  METHODS
  Databases were systematically searched and 1473 possible studies were identified. After initial scrutiny of the article titles and removal of those not relevant, 250 studies were selected for further appraisal. Of these, 211 were excluded after reading the abstracts and a further 18 after reading the full article. This resulted in 21 studies on which to perform a systematic review, with only 12 having sufficient data for meta-analysis. The primary data of the epidemiological studies were extracted as raw numbers. An aggregate effect size, weighted by sample size, was computed to provide an overall effect size across the studies. Risk ratios and 95% confidence intervals (CIs) were calculated. The relative weighted contribution of each study was also assessed.
  
  
  RESULTS
  The overall meta-analytical prevalence for transsexualism was 4.6 in 100,000 individuals; 6.8 for trans women and 2.6 for trans men. Time analysis found an increase in reported prevalence over the last 50 years.
  
  
  CONCLUSIONS
  The overall prevalence of transsexualism reported in the literature is increasing. However, it is still very low and is mainly based on individuals attending clinical services and so does not provide an overall picture of prevalence in the general population. However, this study should be considered as a starting point and the field would benefit from more rigorous epidemiological studies acknowledging current changes in the classification system and including different locations worldwide.
authors.affiliation: Nottingham Centre for Gender Dysphoria, Nottinghamshire Healthcare NHS Trust, 3 Oxford Street, NG1 5BH Nottingham, United Kingdom; School of Sport, Exercise, and Health Sciences, Loughborough University, Loughborough, United Kingdom.
authors.forename: J
authors.initials: J
authors.lastname: Arcelus
authors.affiliation: Nottingham Centre for Gender Dysphoria, Nottinghamshire Healthcare NHS Trust, 3 Oxford Street, NG1 5BH Nottingham, United Kingdom. Electronic address: walterbouman@doctors.org.uk.
authors.forename: W P
authors.initials: WP
authors.lastname: Bouman
authors.affiliation: Centre for Methodology of Educational Research, Katholieke Universiteit, Leuven, Belgium.
authors.forename: W
authors.initials: W
authors.lastname: Van Den Noortgate
authors.affiliation: Faculty of Psychology and Educational Sciences, KU Leuven, Leuven, Belgium.
authors.forename: L
authors.initials: L
authors.lastname: Claes
authors.affiliation: School of Sport, Exercise, and Health Sciences, Loughborough University, Loughborough, United Kingdom.
authors.forename: G
authors.initials: G
authors.lastname: Witcomb
authors.affiliation: Department of Psychiatry, University Hospital of Bellvitge-IDIBELL, Barcelona, Spain; CIBER Fisiopatología Obesidad y Nutrición (CIBERobn), ISCIII, Barcelona, Spain.
authors.forename: F
authors.initials: F
authors.lastname: Fernandez-Aranda
mesh_terms: D003430:Cross-Sectional Studies; D005260:Female; D006801:Humans; D008297:Male; D015995:Prevalence; D014189:Transsexualism / Q000175:diagnosis / Q000453:epidemiology
keywords: Gender dysphoria; Meta-analysis; Population; Systematic review; Transgender