In a recent study published in The Lancet Regional Health-Europe, researchers investigated whether smoking while pregnant or maturity reduces the likelihood of developing type 1 diabetes (T1D) later in life.

Prenatal smoking is expounded to a lower T1D incidence in offspring, possibly on account of variables resembling low birth weight. It may lower the prospect of developing T1D later in life. The mechanism underlying the link is unknown; nevertheless, it might be on account of the immunosuppressive effects of nicotine. If smoke exposure in the course of the prenatal period reduces or delays T1D establishment, it might potentially influence adult-onset diabetes amongst smokers.

Study: Prenatal and adult exposure to smoking and incidence of type 1 diabetes in children and adults–a nationwide cohort study with a family-based design. Image Credit: Monkey Business Images / Shutterstock

Concerning the study

In the current study, researchers examined prenatal smoking exposure and smoking habits during maturity concerning T1D incidence in children and adults.

The study examined T1D prevalence amongst Swedish individuals, concentrating on mother smoking while pregnant and adult smoking. The Swedish National Population, Patient, Prescription, Diabetes, Explanation for Death, Medical Birth, Multigeneration, Military Registers, Labor Market Studies (LISA), and the longitudinal Integration Database for Health Insurance data were analyzed by the researchers. T1D patients were in comparison with their non-diabetic brothers and sisters on the time the cases were detected using cohort and sibling designs.

Conditional logistic regression models were used to estimate the percentages ratios (ORs) of T1D concerning adult and maternal smoking with qualifying sibling groups. As well as, discrete-time proportional hazard regression models were used to find out the hazard ratios (HRs). Covariates adjusted were sex, calendar 12 months, family history of diabetes, maternal body mass index (BMI) for exposure to maternal smoking, or adult BMI. The ORs were sex-adjusted for the age-matched siblings. Adult smoking evaluation adjustments were made for BMI.

The cohort analyses of smokers versus non-smokers and T1D incidence covered individuals from birth (Birth Cohort) or study initiation (Pregnancy and Military Conscription Cohorts) until 30 years of age, diabetes diagnosis, migration, death, or 31 December 2019, whichever occurred first. Individuals born between 1983 and 2014 reported within the Medical Birth Register comprised the Birth Cohort.

The adult smoking analyses included the Military Cohort and the Pregnancy Cohort. The Military Cohort comprised individuals completing military conscription from 1997 to 2010 and having smoking data records within the Medical Birth Register. The Pregnancy Cohort included women who conceived before 30 years of age from 1983 to 2014 and had smoking data recorded within the Medical Birth Register. The study populations were tracked within the Patient, Diabetes, and Prescribed Drug Registers for T1D diagnosis until 30 years of age.

The researchers identified incidental instances of T1D using data from the Diabetes and Patient Registers. They excluded individuals who received diabetes diagnoses and used glucose-lowering medications before baseline. Siblings within the Birth, Military, and Pregnancy Cohorts were linked using the Multigeneration Register. The International Classification of Diseases, tenth revision (ICD-10) codes were used to diagnose diabetes.

Results

The research included 3,170,386 individuals under 31 years with T1D (0.6%) and 1,608,291 adults with diabetes (0.8%). Smoking while pregnant was related to a decreased risk of T1D during youth and young maturity (20 to 24 years of age) but not at an older age. The hazard ratio for adult smoking was 1.1 overall and 1.3 amongst individuals with a history of diabetes within the family. T1D patients showed an increased likelihood of getting diabetic parents, being less educated, obese, and smoking at baseline.

Sibling studies produced comparable findings for maternal cigarette smoking and T1D amongst children, but there was no reduction within the incidence of T1D during maturity. Cohort analyses by age found a 24% to 30% reduced T1D incidence in the kids of smoking moms in comparison with moms who didn’t smoke till 24 years of age, but no difference between the ages of 25 and 30. A corresponding sibling study, which compared individuals with maternal smoke exposure with their unexposed brothers and sisters, found a lower risk until the ages of 10 and 14, a trend toward a lower risk between 15 and 19 years, but no reduction in risk at older ages.

Prenatal smoking was related to a lower incidence of juvenile T1D in those with and and not using a diabetes family history. T1D risks amongst smokers were 1.2, 1.1, and 1.1, belonging to the Pregnancy, Military, and combined cohorts, respectively, with none evidence of dosage-response connections. The outcomes were unaffected by adjusting for maternal smoke. Combining data on maturity and prenatal smoking exposure demonstrated a lower incidence of T1D during maturity only in individuals with maternal smoke exposure but no cigarette smoking habits as adults. The Military Cohort results showed no increase in T1D incidence amongst smokers and snus users.

Overall, the study findings showed that maternal smoking while pregnant reduced T1D development risk in childhood; nevertheless, the association disappeared in maturity. Smoking during maturity didn’t lower T1D risk, with a number of findings even indicating contradictory results. Prenatal exposure to smoking was unrelated to adult-onset T1D risk.