Association Between Environmental Smoke Exposure in Early Life and ADHD-like Behaviors in Chinese Preschoolers: Findings from Population Survey in Shenzhen.

Environmental tobacco smoke (ETS) exposure is a public health concern linked to neurodevelopmental disorders like attention deficit hyperactivity disorder (ADHD). Prior studies link ETS to ADHD, but gaps remain regarding gender differences, critical exposure windows, and dose-response relationships. This study assessed ETS exposure's association with ADHD-like behaviors in Chinese preschoolers, evaluating overall risk, critical periods, dose-response relationships, and gender differences. Analyzing data from 64,472 preschoolers, ETS exposure (prenatal; infancy, 0-1; and early childhood, 1-3 years) was assessed via parent questionnaires, and ADHD-like behaviors were measured using the Conners' Parent Rating Scale-Revised, with associations examined via logistic regression. ETS-exposed children had a 49% higher ADHD-like behavior risk (AOR = 1.49, 95% CI: 1.38-1.62, p < 0.001), with dose-response effects: The risk increased from AOR = 1.25 (95% CI: 1.10-1.40) at low exposure to 2.24 (95% CI: 1.63-3.01) at high exposure. Prenatal (AOR = 1.42, 95% CI: 1.17-1.71) and infancy exposures (AOR = 1.43, 95% CI: 1.05-1.90) showed the strongest associations, while early childhood exposure (1-3 years) was non-significant (AOR = 1.04, 95% CI: 0.82-1.29). No gender-specific differences were observed. Early-life ETS exposure, particularly prenatally and in infancy, elevates ADHD-like behavior risk in preschoolers, demonstrating dose-response trends without gender disparity, highlighting the need for universal strategies to reduce such exposures.