Maternal smoking linked to reduced childhood type 1 diabetes risk, effects fade in adulthood

In a recently published study, Dr Lancet Regional Health-EuropeResearchers have investigated whether smoking during pregnancy or adulthood reduces the risk of developing type 1 diabetes (T1D) later in life.

Prenatal smoking is associated with lower T1D incidence in offspring, possibly due to variables such as low birth weight. It may also reduce the chance of developing T1D later in life. The mechanism underlying the link is unknown; However, this may be due to the immunosuppressive effects of nicotine. If exposure to smoking during the prenatal period reduces or delays the establishment of T1D, this may affect adult-onset diabetes in smokers.

Study: Prenatal and adult smoking exposure 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

About the study

In the current study, researchers examined prenatal smoking exposure and smoking habits during adulthood in relation to T1D incidence in children and adults.

The study examined the prevalence of T1D in Swedish individuals, focusing on maternal smoking during pregnancy and adult smoking. Longitudinal integration databases for Swedish national population, patient, prescription, diabetes, cause of death, medical birth, multigenerational, military register, labor market study (LISA), and health insurance data were analyzed by the researchers. T1D patients were compared with their non-diabetic brothers and sisters when cases were identified using cohort and sibling designs.

Conditional logistic regression models were used to estimate odds ratios (ORs) of T1D related to adult and maternal smoking with eligible sibling groups. In addition, discrete-time proportional hazards regression models were used to determine hazard ratios (HRs). Adjusted covariates were gender, calendar year, family history of diabetes, maternal body mass index (BMI) for maternal smoking exposure, or adult BMI. ORs were sex-adjusted for age-matched siblings. Adult smoking analyzes were adjusted for BMI.

Cohort analysis of smokers versus nonsmokers and T1D incidence from birth (birth cohort) or study initiation (pregnancy and military enlistment cohort) to age 30 years, including diabetes diagnosis, immigration, death, or incident on December 31, 2019. Birth cohorts include individuals born between 1983 and 2014 in the first medical birth register.

Adult smoking analyzes included military cohorts and pregnancy cohorts. The military cohort includes individuals who completed military service from 1997 to 2010 and had smoking data recorded in the Medical Birth Register. The pregnancy cohort included women who conceived before the age of 30 from 1983 to 2014 and had smoking data recorded in the Medical Birth Register. The study population was tracked in patients up to age 30 years, diagnosed with diabetes and T1D in prescribed medication registries.

The researchers identified concomitant instances of T1D using data from diabetes and patient registries. They excluded individuals who received a diagnosis of diabetes and used glucose-lowering medications before baseline. Siblings were linked at birth, military and pregnancy using multigenerational registers. International Classification of Diseases, Tenth Revision (ICD-10) codes were used to diagnose diabetes.

result

The study included 3,170,386 people under 31 years of age with T1D (0.6%) and 1,608,291 adults with diabetes (0.8%). Smoking during pregnancy was associated with a reduced risk of T1D in adolescence and young adulthood (aged 20 to 24 years) but not at older ages. The hazard ratio for smoking in adults was 1.1 overall and 1.3 among individuals with a family history of diabetes. Patients with T1D were more likely to have diabetic parents, be less educated, obese, and smoke at baseline.

Sibling studies have produced comparable results for maternal cigarette smoking and T1D in children, but no reduction in the prevalence of T1D during adulthood. Cohort analysis by age showed a 24% to 30% reduced incidence of T1D in children of mothers who smoked compared with mothers who never smoked by age 24, but no difference between ages 25 and 30. A similar sibling study, which compared individuals exposed to maternal smoking with their unexposed brothers and sisters, found a lower risk between ages 10 and 14, a trend toward lower risk between ages 15 and 19, but no reduction in risk at older ages. .

Prenatal smoking was associated with a lower incidence of juvenile T1D in those with and without a diabetes family history. T1D risk among smokers was 1.2, 1.1, and 1.1, with no evidence of a dose-response association belonging to the pregnancy, military, and combined cohorts, respectively. Results were not affected by adjusting for maternal smoking. Combining data on adult and prenatal smoking exposure demonstrated a lower incidence of T1D in adults only among individuals exposed to maternal smoking but not cigarette smoking as adults. Results from a military cohort did not show increased T1D prevalence among smokers and snus users.

Overall, the study results showed that maternal smoking during pregnancy reduces the risk of developing T1D in childhood; However, the association disappears in adulthood. Smoking in adulthood did not reduce T1D risk, with some results even suggesting conflicting results. Prenatal exposure to smoking was not associated with adult-onset T1D risk.