title: The association between major depression prevalence and sex becomes weaker with age.
abstract: BACKGROUND
  Women have a higher prevalence of major depressive episodes (MDE) than men, and the annual prevalence of MDE declines with age. Age by sex interactions may occur (a weakening of the sex effect with age), but are easily overlooked since individual studies lack statistical power to detect interactions. The objective of this study was to evaluate age by sex interactions in MDE prevalence.
  
  
  METHODS
  In Canada, a series of 10 national surveys conducted between 1996 and 2013 assessed MDE prevalence in respondents over the age of 14. Treating age as a continuous variable, binomial and linear regression was used to model age by sex interactions in each survey. To increase power, the survey-specific interaction coefficients were then pooled using meta-analytic methods.
  
  
  RESULTS
  The estimated interaction terms were homogeneous. In the binomial regression model I (2) was 31.2 % and was not statistically significant (Q statistic = 13.1, df = 9, p = 0.159). The pooled estimate (-0.004) was significant (z = 3.13, p = 0.002), indicating that the effect of sex became weaker with increasing age. This resulted in near disappearance of the sex difference in the 75+ age group. This finding was also supported by an examination of age- and sex-specific estimates pooled across the surveys.
  
  
  CONCLUSIONS
  The association of MDE prevalence with sex becomes weaker with age. The interaction may reflect biological effect modification. Investigators should test for, and consider inclusion of age by sex interactions in epidemiological analyses of MDE prevalence.
authors.affiliation: Department of Community Health Sciences, University of Calgary, 3280 Hospital Drive NW, Calgary, AB, T2N 4Z6, Canada. patten@ucalgary.ca.|Department of Psychiatry, University of Calgary, 3280 Hospital Drive NW, Calgary, AB, T2N4Z6, Canada. patten@ucalgary.ca.|Mathison Centre for Research and Education in Mental Health, Hotchkiss Brain Institute, 3280 Hospital Drive NW, Calgary, AB, T2N4Z6, Canada. patten@ucalgary.ca.|Alberta Innovates, Health Solutions, 1500, 10104 - 103 Avenue, Edmonton, AB, T5J4A7, Canada. patten@ucalgary.ca.
authors.forename: Scott B
authors.initials: SB
authors.lastname: Patten
authors.affiliation: Department of Community Health Sciences, University of Calgary, 3280 Hospital Drive NW, Calgary, AB, T2N 4Z6, Canada.
authors.forename: Jeanne V A
authors.initials: JV
authors.lastname: Williams
authors.affiliation: Department of Community Health Sciences, University of Calgary, 3280 Hospital Drive NW, Calgary, AB, T2N 4Z6, Canada.
authors.forename: Dina H
authors.initials: DH
authors.lastname: Lavorato
authors.affiliation: Department of Community Health Sciences, University of Calgary, 3280 Hospital Drive NW, Calgary, AB, T2N 4Z6, Canada.|Department of Psychiatry, University of Calgary, 3280 Hospital Drive NW, Calgary, AB, T2N4Z6, Canada.|Mathison Centre for Research and Education in Mental Health, Hotchkiss Brain Institute, 3280 Hospital Drive NW, Calgary, AB, T2N4Z6, Canada.
authors.forename: Jian Li
authors.initials: JL
authors.lastname: Wang
authors.affiliation: Department of Community Health Sciences, University of Calgary, 3280 Hospital Drive NW, Calgary, AB, T2N 4Z6, Canada.|Department of Psychiatry, University of Calgary, 3280 Hospital Drive NW, Calgary, AB, T2N4Z6, Canada.|Mathison Centre for Research and Education in Mental Health, Hotchkiss Brain Institute, 3280 Hospital Drive NW, Calgary, AB, T2N4Z6, Canada.
authors.forename: Andrew G M
authors.initials: AG
authors.lastname: Bulloch
authors.affiliation: Department of Community Health Sciences, University of Calgary, 3280 Hospital Drive NW, Calgary, AB, T2N 4Z6, Canada.|Department of Clinical Neurosciences, University of Calgary, 1403 - 29 Street NW, Calgary, AB, T2N2T9, Canada.
authors.forename: Tolulope
authors.initials: T
authors.lastname: Sajobi
mesh_terms: D000293:Adolescent; D000328:Adult; D017677:Age Distribution; D000368:Aged; D002170:Canada / Q000453:epidemiology; D003430:Cross-Sectional Studies; D003865:Major Depressive Disorder / Q000453:epidemiology*; D005260:Female; D006306:Health Surveys; D006801:Humans; D008297:Male; D008875:Middle Aged; D015995:Prevalence; D017678:Sex Distribution; D055815:Young Adult
keywords: Age effects; Cross-sectional study; Epidemiologic study; Epidemiology; Major depressive episode; Population study; Sex differences