Tobacco smoke exposure early in life ups paediatric IBD risk

A Scandinavian population-based birth cohort study reveals that children who were exposed to tobacco smoke during their early childhood have an increased risk of developing inflammatory bowel disease (IBD) later in life.

“Using questionnaire data from two similar large-scale prospective cohorts, we saw that children of mothers who had a high level of smoking during their pregnancy and being exposed to environmental tobacco smoke during the first year of life increased the risk of IBD in children,” said Ida Sigvardsson, a PhD student from the University of Gothenburg in Sweden, during her presentation at ESPGHAN 2024.

Having a mum who smoked ≥6 cigarettes per day on average during her pregnancy increased the risk of IBD in the child (pooled adjusted hazard ratio [adjHR], 1.6, 95 percent confidence interval [CI], 1.06–2.38). This finding, according to Sigvardsson, implies that numbers do matter and underscores the importance of the amount of cigarettes that mums smoked during pregnancy.

Likewise, exposure to environmental tobacco smoke by the age of 1 year also led to an increased risk of IBD in children (pooled adjHR, 1.32, 95 percent CI, 1.03–1.69). [Sigvardsson, et al, ESPGHAN 2024]

For the rest of the exposures evaluated, no significant associations were found. These variables were maternal smoking during pregnancy (pooled adjHR, 1.3), maternal smoking 1–5 cigarettes per day (pooled adjHR, 1.09), tobacco smoke exposure by the age of 3 years (pooled adjHR, 1.26), maternal environmental tobacco smoke exposure during pregnancy (pooled adjHR, 0.88), paternal smoking during pregnancy (pooled adjHR, 1.29), and maternal smoking 3 months prior to pregnancy (pooled adjHR, 1.08).

Kicking the butt is key

Sigvardsson pointed out that most of the literature substantiating the link between tobacco smoke exposure and IBD risk are conducted in cohorts of adult individuals via retrospective analyses. “Hence, we [sought to] examine if early life environmental tobacco smoke exposure affected the risk of later IBD in children.”

Sigvardsson and colleagues retrieved data on IBD diagnosis from two Scandinavian birth cohorts: All Babies in Southeast Sweden (ABIS; n=15,843) and the Norwegian Mother, Father and Child Cohort Study (MoBa; n=99,820).

In ABIS, the mean age at end of follow-up was 22.2 years; in MoBa, it was 16.4 years. About 1–2 percent of the children had a parent who had IBD and roughly 10 percent of the mums smoked at some point during pregnancy.

After nearly 2 million person-years of total follow-up time, 444 children had developed IBD by the end of the follow-up period.

“Together with additional supporting evidence, [these data] might help us in the future to identify individuals at an increased risk of IBD,” said Sigvardsson.

“[These also] highlight the importance of informing parents about smoking cessation during the children’s early life to minimize children’s exposure to a harmful environment,” she concluded.