title: Birth weight and risk of type 2 diabetes: a systematic review.
abstract: BACKGROUND
  Low birth weight is implicated as a risk factor for type 2 diabetes. However, the strength, consistency, independence, and shape of the association have not been systematically examined.
  
  
  OBJECTIVE
  To conduct a quantitative systematic review examining published evidence on the association of birth weight and type 2 diabetes in adults.
  
  
  METHODS
  Relevant studies published by June 2008 were identified through literature searches using EMBASE (from 1980), MEDLINE (from 1950), and Web of Science (from 1980), with a combination of text words and Medical Subject Headings. Studies with either quantitative or qualitative estimates of the association between birth weight and type 2 diabetes were included.
  
  
  METHODS
  Estimates of association (odds ratio [OR] per kilogram of increase in birth weight) were obtained from authors or from published reports in models that allowed the effects of adjustment (for body mass index and socioeconomic status) and the effects of exclusion (for macrosomia and maternal diabetes) to be examined. Estimates were pooled using random-effects models, allowing for the possibility that true associations differed between populations.
  
  
  RESULTS
  Of 327 reports identified, 31 were found to be relevant. Data were obtained from 30 of these reports (31 populations; 6090 diabetes cases; 152 084 individuals). Inverse birth weight-type 2 diabetes associations were observed in 23 populations (9 of which were statistically significant) and positive associations were found in 8 (2 of which were statistically significant). Appreciable heterogeneity between populations (I(2) = 66%; 95% confidence interval [CI], 51%-77%) was largely explained by positive associations in 2 native North American populations with high prevalences of maternal diabetes and in 1 other population of young adults. In the remaining 28 populations, the pooled OR of type 2 diabetes, adjusted for age and sex, was 0.75 (95% CI, 0.70-0.81) per kilogram. The shape of the birth weight-type 2 diabetes association was strongly graded, particularly at birth weights of 3 kg or less. Adjustment for current body mass index slightly strengthened the association (OR, 0.76 [95% CI, 0.70-0.82] before adjustment and 0.70 [95% CI, 0.65-0.76] after adjustment). Adjustment for socioeconomic status did not materially affect the association (OR, 0.77 [95% CI, 0.70-0.84] before adjustment and 0.78 [95% CI, 0.72-0.84] after adjustment). There was no strong evidence of publication or small study bias.
  
  
  CONCLUSIONS
  In most populations studied, birth weight was inversely related to type 2 diabetes risk.
authors.affiliation: Division of Community Health Sciences, St George's, University of London, Cranmer Terrace, London SW17 0RE, England. p.whincup@sgul.ac.uk
authors.forename: Peter H
authors.initials: PH
authors.lastname: Whincup
authors.forename: Samantha J
authors.initials: SJ
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authors.forename: Christopher G
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authors.lastname: Owen
authors.forename: Rachel
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authors.forename: Derek G
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authors.forename: Sonoko
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authors.forename: Santosh K
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authors.forename: Bryndís E
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authors.forename: Sofia
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authors.lastname: Carlsson
authors.forename: Susanne R
authors.initials: SR
authors.lastname: de Rooij
authors.forename: Roland F
authors.initials: RF
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authors.forename: Johan G
authors.initials: JG
authors.lastname: Eriksson
authors.forename: Bonita
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authors.forename: Caroline
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authors.lastname: Fall
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authors.forename: Valdemar
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authors.lastname: Grill
authors.forename: Vilmundur
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authors.lastname: Gudnason
authors.forename: Sonia
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authors.lastname: Hulman
authors.forename: Elina
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authors.lastname: Hyppönen
authors.forename: Mona
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authors.lastname: Jeffreys
authors.forename: Debbie A
authors.initials: DA
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authors.forename: David A
authors.initials: DA
authors.lastname: Leon
authors.forename: Junichi
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authors.lastname: Minami
authors.forename: Gita
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authors.lastname: Mishra
authors.forename: Clive
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authors.lastname: Osmond
authors.forename: Chris
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authors.lastname: Power
authors.forename: Janet W
authors.initials: JW
authors.lastname: Rich-Edwards
authors.forename: Tessa J
authors.initials: TJ
authors.lastname: Roseboom
authors.forename: Harshpal Singh
authors.initials: HS
authors.lastname: Sachdev
authors.forename: Holly
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authors.lastname: Syddall
authors.forename: Inga
authors.initials: I
authors.lastname: Thorsdottir
authors.forename: Mauno
authors.initials: M
authors.lastname: Vanhala
authors.forename: Michael
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authors.lastname: Wadsworth
authors.forename: Donald E
authors.initials: DE
authors.lastname: Yarbrough
mesh_terms: D000328:Adult; D000368:Aged; D001724:Birth Weight; D003924:Diabetes Mellitus, Type 2 / Q000453:epidemiology*; D006801:Humans; D008875:Middle Aged; D012306:Risk