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

Abstract

AimsOur 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.MethodsWe 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.ResultsWe 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, I 2=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, I 2 = 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, I 2 = 0%) nor paternal (n = 6, RR 0.90, 0.70–1.17, I 2 = 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, I 2 = 71%).ConclusionsMaternal 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.RegistrationProspero CRD42021236717.