title: Sex differences in insomnia: a meta-analysis.
abstract: OBJECTIVE
  Most but not all epidemiologic evidence suggests a female predisposition of insomnia. We applied meta-analytic methods to investigate sex differences in the risk of insomnia among the published epidemiologic studies.
  
  
  METHODS
  Meta-analysis with Comprehensive Meta-Analysis (Englewood, NJ); 9 different analyses were performed to investigate the sex difference of insomnia among different conditions.
  
  
  METHODS
  A comprehensive search of the medical literature databases was performed to identify epidemiologic studies of insomnia. A rolling snowball method was also used.
  
  
  METHODS
  General population.
  
  
  METHODS
  N/A.
  
  
  RESULTS
  Thirty-one related papers were found, but 2 studies only reported the subtype prevalence of insomnia. All other studies (1,265,015 participants, female/male: 718,828/546,187) were included in the overall analysis of insomnia. A risk ratio of 1.41 [95% confidence interval: 1.28-1.55] for female versus male was found. The female excess in the risk of insomnia in large and quality studies was much higher than that of small and nonquality studies. The trend of female predisposition was consistent and progressive across age, with more significance in the elderly. The use of various criteria and frequency and duration of insomnia did not influence the predisposition of female in the risk of developing insomnia. Although obvious female excess in the risk of insomnia exists among different regions, there was a relatively lower female excess in East Asia.
  
  
  CONCLUSIONS
  This meta-analysis confirmed a female predisposition of insomnia. Further studies will be needed to examine the roles of different factors in leading to the sex difference of insomnia.
authors.affiliation: Department ofPsychiatry, Shatin Hospital, The Chinese University of Hong Kong, Shatin, Hong Kong SAR, Peoples Republic China.
authors.forename: Bin
authors.initials: B
authors.lastname: Zhang
authors.forename: Yun-Kwok
authors.initials: YK
authors.lastname: Wing
mesh_terms: D005260:Female; D006801:Humans; D008297:Male; D011159:Population Surveillance / Q000379:methods; D015995:Prevalence; D017678:Sex Distribution; D007319:Sleep Initiation and Maintenance Disorders / Q000453:epidemiology*