Maternal Smoking During Pregnancy Linked to Decreased Risk of Childhood Type 1 Diabetes, Effects Diminish in Adulthood


In a recent study, researchers have found a potential link between maternal smoking during pregnancy and a decreased incidence of type 1 diabetes (T1D) in children. The study suggests that prenatal smoking may lower the chances of developing T1D later in life. However, the underlying mechanism for this association is still unknown, although researchers speculate that it could be due to the immunosuppressive effects of nicotine. Furthermore, if smoke exposure during pregnancy reduces or delays the onset of T1D, it may have implications for the development of adult-onset diabetes among smokers.

The study focused on examining the prevalence of T1D among individuals in Sweden, specifically looking at maternal smoking during pregnancy and smoking habits during adulthood. The researchers analyzed various databases, including the Swedish National Population, Patient, Prescription, Diabetes, Cause of Death, Medical Birth, Multigeneration, Military Registers, Labor Market Studies (LISA), and the longitudinal Integration Database for Health Insurance data. They compared T1D patients to their non-diabetic siblings using cohort and sibling designs.

Through conditional logistic regression models, the researchers estimated the odds ratios (ORs) of T1D in relation to adult and maternal smoking, taking into account sibling groups. Discrete-time proportional hazard regression models were also used to determine the hazard ratios (HRs). The analyses adjusted for variables such as sex, calendar year, family history of diabetes, and maternal or adult body mass index (BMI). Additionally, the ORs were age-matched for siblings of the same sex and the adult smoking analysis adjusted for BMI.

The cohort analyses included individuals from birth or study initiation until 30 years of age, diabetes diagnosis, migration, death, or December 31, 2019, whichever came first. The Birth Cohort consisted of individuals born between 1983 and 2014, while the Military Cohort comprised individuals who completed military conscription from 1997 to 2010 with smoking data records. The Pregnancy Cohort included women who conceived before 30 years of age from 1983 to 2014 with smoking data recorded. The researchers tracked these study populations in the Patient, Diabetes, and Prescribed Drug Registers for T1D diagnosis until 30 years of age.

The researchers identified cases of T1D using data from the Diabetes and Patient Registers, excluding individuals who had already received diabetes diagnoses or used glucose-lowering medications before the start of the study. Siblings in the Birth, Military, and Pregnancy Cohorts were linked using the Multigeneration Register, and the International Classification of Diseases, tenth revision (ICD-10) codes were used to diagnose diabetes.

The study included a total of 3,170,386 individuals under 31 years with T1D (0.6%) and 1,608,291 adults with diabetes (0.8%). The findings showed that smoking during pregnancy was associated with a decreased risk of T1D during childhood and young adulthood (20 to 24 years of age), but not at older ages. The hazard ratio for adult smoking was 1.1 overall and 1.3 among individuals with a family history of diabetes. Other factors associated with T1D included having diabetic parents, lower education levels, obesity, and smoking at baseline.

Sibling studies confirmed the association between maternal smoking and decreased T1D risk in children but did not show a reduction in T1D incidence during adulthood. Cohort analyses by age demonstrated a 24% to 30% lower incidence of T1D in children of smoking mothers compared to non-smoking mothers until 24 years of age, but no difference between the ages of 25 and 30. Similarly, the sibling study showed a lower risk until ages 10 and 14, and a trend toward lower risk between ages 15 and 19, but no reduction in risk at older ages.

The study also found that prenatal smoking was associated with a lower incidence of juvenile T1D, regardless of whether there was a family history of diabetes. The T1D risks among smokers were consistent across the Pregnancy and Military Cohorts. However, there was no evidence of dose-response relationships. Combining data on prenatal and adult smoking exposure showed a lower incidence of T1D during adulthood only among individuals with prenatal smoke exposure but no smoking habits as adults. The Military Cohort analysis showed no increase in T1D incidence among smokers and snus users.

In conclusion, the study suggests that maternal smoking during pregnancy is linked to a reduced risk of T1D development in childhood. However, this association diminishes in adulthood. Smoking during adulthood does not appear to lower the risk of T1D, with some findings even suggesting contradictory results. Prenatal smoking does not seem to influence the risk of adult-onset T1D.



  1. Source: Coherent Market Insights, Public sources, Desk research
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