Dental caries linked to gestational and early-life secondhand smoke exposure

Few studies have investigated how different exposure windows - gestational, early postnatal, and current - of secondhand smoke (SHS) contribute to early childhood caries (ECC). Understanding these critical windows is essential for designing targeted interventions. We evaluated the association between SHS exposure and ECC among preschoolers.

This study was nested within the prospective birth cohort (HAPIN trial) conducted in southern India (2018-2020). Comprehensive data on exposure, lifestyle, and health were collected at multiple maternal and child time points. Between April and September 2023, dental caries and current exposure were assessed in children aged 3 - 5 years by a trained dentist using standardized, calibrated methods. SHS exposure was measured using questionnaires and urinary nicotine metabolites (cotinine, 3-hydroxycotinine). Negative binomial hurdle models were used to assess associations between SHS exposure and ECC prevalence.

Among 712 participants (mean age: 4.01 ± 0.45 years; 53.4% boys), 478 children (67.2%) were diagnosed with ECC. Children exposed to SHS (urinary nicotine equivalents - sum of cotinine and 3-hydroxycotinine) during the gestational period demonstrated significantly higher prevalence of caries than their unexposed counterparts, with an incidence rate ratio (IRR) of 1.29 (95% CI, 1.18-1.42); second trimester was identified as a critical exposure window. Similarly, postnatal exposure increased ECC risk (IRR, 1.19; 95% CI, 1.08-1.31). Paternal smoking significantly elevated ECC prevalence, with children whose fathers smoked ≥11 cigarettes/day showing higher odds of ECC (odds ratio (OR), 1.90; 95% CI, 1.10-3.41). Urinary nicotine metabolites exhibited a dose-response relationship with ECC, showing the strongest association during pregnancy. Children classified as slow metabolizers were more vulnerable to third-trimester SHS exposure (OR, 1.74; 95% CI, 1.15-2.64).

SHS exposure from pregnancy through early childhood was linked to higher odds of developing dental caries.

Findings underscore another precarious health risk associated with SHS exposure and highlight the need for integrated oral-environmental health prevention strategies.