1. In a pre-birth prospective cohort study, early childhood smoke exposure, but not prenatal smoke exposure, was associated with altered neurocognitive outcomes.

2. Neither prenatal nor early childhood smoke exposure affected measures of attention deficit hyperactivity disorder (ADHD).

Evidence Rating Level: 2 (Good)

Study Rundown: Tobacco smoke is a well-known teratogen, with some studies suggesting that exposure to smoke prenatally or in early childhood is associated with altered neurocognition in children. This study aimed to further study the associations between prenatal and early childhood smoke exposure and neurodevelopment and behavioral functioning. Researchers utilized data from a previous pre-birth cohort study that collected maternal data and serum samples. Mother-child pairs were re-engaged to participate in neurocognitive testing and quantification of childhood smoke exposure through the collection of saliva metabolites. When controlling for covariates, prenatal smoke exposure was not associated with altered neurocognitive performance as measured by the NIH Toolbox or measures of ADHD by the Behavioral Assessment System for Children, 2nd edition (BASC-2). In contrast, early childhood exposure to smoke was associated with changes in various NIH toolbox scores for cognitive performance, inhibitor control and attention, cognitive flexibility, episodic memory, and receptive language development. Early childhood smoke exposure was not associated with abnormal BASC-2 measures. One study limitation is that nicotine metabolites in the maternal serum and child saliva have a half-life of 14-15 hours and are impacted by a variety of factors, and therefore may not be an accurate measure of long-term smoke exposure throughout pregnancy or childhood. Overall, this study provides evidence that childhood tobacco smoke exposure may negatively influence neurocognitive outcomes.

Click here to read the article in Journal of Pediatrics

Relevant Reading: Association between secondhand smoke exposure at home and cognitive performance among rural primary school children in Malaysia

In-Depth [prospective cohort study]: Participants were previously enrolled in the pre-birth cohort study, specifically the Newborn Epigenetic STudy (NEST) in the southeastern United States, with 2,595 pregnant women enrolled from prenatal clinics serving Duke University Hospital and Durham Regional Hospital Obstetrics facilities between April 2005 and June 2011. Maternal blood samples were collected at enrollment, with a recording of survey health data, nutritional status, stressors, and lifestyle behaviors. This study re-contacted mothers of the NEST study between 2013-2019 to enroll children > 3 years old, with 386 mother-child pairs participating in the follow-up study. Prenatal smoke exposure was measured by cotinine, a metabolite of nicotine, in maternal plasma blood samples at the time of NEST enrollment. Early childhood smoke exposure was measured by cotinine in children’s saliva samples during clinic visits. Outcomes included cognitive performance measured by the NIH Toolbox and ADHD measured by BASC-2. After controlling for covariates, prenatal cotinine concentration was not associated with changes in NIH Toolbox scores or BAS-C measures. In contrast, childhood exposure to smoke was associated with lower cognitive performance (p<0.001), inhibitor control and attention (p=0.006), cognitive flexibility (p=0.03), episodic memory (p=0.02), and receptive language development (p=0.01). Childhood smoke exposure was not associated with changes in BASC-2 measures.

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