Researchers published the study covered in this summary on Preprints with The Lancet as a preprint that has not yet been peer reviewed.
Key Takeaways
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In a nationwide Swedish study of more than 3 million people, prenatal exposure to smoking was significantly associated with a reduced risk for developing type 1 diabetes during childhood, but not after the offspring turned 25 years old.
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Young adults who smoked did not have a reduced risk for developing type 1 diabetes, and the evidence showed a signal that the risk for adult-onset type 1 diabetes may have increased in this group.
Why This Matters
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Prenatal exposure to smoking has previously been linked to a reduced risk of type 1 diabetes in children compared with those with nonsmoking mothers, but no prior reports have addressed whether this protection continues into adulthood or applies to adults who themselves smoke.
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This is the first study to investigate maternal smoking during pregnancy in relation to type 1 diabetes incidence in offspring beyond childhood.
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The authors cautioned that the clinical significance of their findings was “difficult to see” considering the many adverse effects from smoking during pregnancy. They instead highlighted that their findings add to understanding the etiology of type 1 diabetes.
Study Design
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The study used data collected by Swedish national registries for 3,176,072 people born from 1983 to 2014, and on all 1,209,618 women who gave birth to a child during this period and had information recorded on their smoking history during pregnancy. The birth cohort included 18,789 people with incident type 1 diabetes before they were 31 years old, including 16,275 people who developed type 1 diabetes by the time they were 18 years old.
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A second analysis focused on incident diabetes and adult smoking among 1,608,291 people 19 to 30 years old and followed until age 30 or the year 2019, of whom 1274 developed type 1 diabetes.
Key Results
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Maternal smoking during pregnancy was significantly associated with a lower incidence of type 1 diabetes in children 0 to 18 years old compared with children born to nonsmoking mothers, with a hazard ratio of 0.76. For offspring 19 to 30 years old, the hazard ratio for incident type 1 diabetes was also significant, 0.88.
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The analysis showed no dose-response relationship between the amount of maternal smoking and diabetes incidence in the offspring, and adjustment for body weight index and smoking by the offspring themselves had no effect on the observed associations.
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The data showed a 22% to 29% lower incidence of type 1 diabetes in the offspring of smoking vs nonsmoking mothers until they were 24 years old, but no difference existed among offspring who were 25 to 30 years old.
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A personal history of smoking was significantly associated with incident type 1 diabetes in people with a family history of diabetes with a significant hazard ratio of 1.34, but no significant association existed for those without this family history.
Limitations
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The study relied on self-reported smoking behavior, which may have especially underestimated maternal smoking during pregnancy.
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The study lacked information on paternal smoking during pregnancy or childhood.
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The study used an exclusively Swedish population, so generalizability to other populations is not clear.
Disclosures
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The study received partial support from the Novo Nordisk Foundations as well as from several noncommercially affiliated sources.
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The authors have disclosed no relevant financial relationships.
This is a summary of a preprint research study “Prenatal and Adult Exposure to Smoking and Incidence of Type 1 Diabetes in Children and Adults — A Nationwide Study with a Family-Based Design,” by researchers at the Karolinska Institute in Stockholm on Preprints with The Lancet and provided to you by Medscape. This study has not yet been peer reviewed. The full text of the study can be found on https://www.ssrn.com/index.cfm/en/the-lancet/.
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