Children exposed to secondhand smoke from pregnancy through early childhood may have greater odds of developing caries, according to a study recently published in the Journal of Dentistry.
The study highlights the need to prioritize oral-environmental prevention strategies, as well as strong public health policies, the authors wrote.
“Our results suggest that SHS (secondhand smoke) may directly impair the developing dentition, with effects spanning gestational and early childhood developmental periods,” wrote the authors, led by Andres Cardena, PhD, of the department of pediatrics at Stanford University in Stanford, CA (J Dent, May 9, 2026, 106743).
Though the number of tobacco users has fallen since 2000, about 1.2 billion were users in 2024. However, 1 in 5 adults worldwide become addicted to tobacco, according to the World Health Organization.
To investigate the link between secondhand smoke and early childhood caries in preschoolers, a study based on a prospective birth cohort in southern India between 2018 and 2020 was conducted. At multiple maternal-child time points, data on smoke exposure, health, and lifestyle were collected from the 712 participants, according to the study.
Between April and September 2023, a dentist measured current exposure and tooth decay in children ages 3 to 5. Questionnaires and urinary nicotine metabolites (cotinine, 3-hydroxycotinine) were used to measure secondhand smoke exposure. Two-part statistical models were used to assess correlations between caries and smoke exposure, the authors wrote.
Among the 712 children studied, 478 -- or about 67% -- were diagnosed with caries. Those exposed to secondhand smoke during gestation showed a much higher prevalence of tooth decay than children who were not, with an incidence rate ratio (IRR) of 1.29 (95% confidence interval [CI], 1.18 to 1.42). Furthermore, the most critical exposure window was during the second trimester. Also, early childhood caries risk rose during postnatal exposure (IRR, 1.19; 95% CI, 1.08 to 1.31), according to the study's authors.
Children whose father smoked experienced a significantly increased prevalence of caries. The children whose fathers smoked 11 cigarettes or more daily demonstrated greater odds of caries (odds ratio [OR], 1.90; 95% CI, 1.10 to 3.41).
Finally, urinary nicotine metabolites revealed a dose-response relationship with caries, showing the most robust correlation during pregnancy. Children who were considered slow metabolizers, the study's authors wrote, were more vulnerable to smoke exposure during the third trimester (OR, 1.74; 95% CI, 1.15 to 2.64).
However, the study had limitations. The lack of data regarding multiunit properties -- where smoke works its way from nearby units -- may limit generalizability, the authors acknowledged.
“This study provides longitudinal, biomarker-based evidence that both prenatal and early-life SHS exposure increase the risk of ECC (early childhood caries),” Cardena and colleagues wrote.
