Parental smoking, type 1 diabetes, and islet autoantibody positivity in the offspring: A systematic review and meta‐analysis

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Abstract
Aims: Our aim was to synthesize current evidence on the association between parental smoking and incidence of type 1 diabetes and islet autoantibody positivity (IA) in the offspring by conducting a systematic review and meta‐analysis.Methods: We searched Medline, Embase, and Cochrane Library until January 21, 2021, for human studies with parental tobacco use as exposure, type 1 diabetes or IA as outcome, and hazard, risk, or odds ratios as effect estimates. Summary relative risks (RR) and 95% confidence intervals (CI) were estimated with random‐effects models. Heterogeneity was quantified with the I2 statistic, bias with the ROBINS‐I tool, and the certainty of evidence with the GRADE tool.Results: We identified 535 records of which 23 were eligible including 25 927 cases of type 1 diabetes. Maternal smoking during pregnancy was associated with a reduced risk of type 1 diabetes (n = 22, RR 0.78, CI 0.71–0.86,I2=69%). Including only studies with low to moderate risk of bias indicated similar results with less heterogeneity (n = 14, RR 0.73, CI 0.68–0.79,I2 = 44%). The certainty of evidence was graded as high. There was no clear association between type 1 diabetes and neither maternal (n = 6, RR 0.95, CI 0.78–1.14,I2 = 0%) nor paternal (n = 6, RR 0.90, 0.70–1.17,I2 = 68%) smoking during childhood. Furthermore, the association between maternal smoking during pregnancy and IA was weak (n = 4, RR 0.86, CI 0.44–1.65,I2 = 71%).Conclusions: Maternal smoking during pregnancy may reduce the risk of type 1 diabetes in the offspring. Further studies are needed to elucidate potential mechanisms underlying this association.Registration: Prospero CRD42021236717.
Funding Information
  • Forskningsrådet för hälsa, arbetsliv och välfärd
  • Vetenskapsrådet
  • Novo Nordisk Fonden
  • Diabetesfonden

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