Postnatal Smoke Exposure Likely Significant Risk Factor for ADHD in Children

Julia Schecter, PhD

Secondhand exposure to smoke may have more of an impact on a child’s hyperactivity than prenatal exposure, according to findings presented at the 2021 American Professional Society of ADHD and Related Disorders (APSARD) Annual Virtual Meeting.

The study, led by Julia Schecter, PhD, Duke University School of Medicine, performed various measures to explore the relationship between postnatal exposure and child behavior.

Further, the team compared the effects of postnatal, secondhand smoke with prenatal exposure.

“The relationship between smoke exposure and hyperactivity is complex; no studies have used objective measures to evaluate these associations,” Schecter and colleagues wrote.

Prenatal versus Postnatal Smoke Exposure and Hyperactivity

The investigators evaluated mother-child dyads (n = 272), which were taken from the Newborn Epigenetic STudy (NEST). The longitudinal study examined the relationship between prenatal exposure to smoke and early childhood developmental outcomes.

Investigators from NEST then analyzed blood samples for cotinine, a metabolite of nicotine. In a follow-up study conducted in Schecter's team's lab, a total of 289 children (mean age, 7.4 years; 53% female) provided saliva samples, which were also analyzed for cotinine.

The children also wore accelerometers that measured Moderate-to-Vigorous Physical Activity (MVPA).

Also measured during follow-up were BMI and hyperactivity, which was assessed by mothers and teachers (n = 181) using the Behavior Assessment System for Children (BASC).

The invesitgators noted variation in race among children in the sample—with 61.4% identifying as African American, 31.6% Caucasian, 7.7% Asian, and 5.5% identifying as more than one race.

Using multiple regression and controlling for relevant covariates, the investigators reported that secondhand smoke (B = .17, t(215) = 2.37, P =.02) was largely associated with MVPA. However, this not the case for prenatal smoke exposure (P = .96).

Furthermore, secondhand smoke was associated with BASC scores as rated by parents (B =. 17, t(215) = 2.37, P =.02) and teachers (B=.18, t(146)=2.07, P = .04), when controlling for prenatal exposure.

There was no association between these scores and prenatal exposure (P = .58).

The investigators also noted there was no significant association between MVPA and BASC scores or MVPA and child BMI, findings which they considered surprising.

“Results indicate secondhand smoke may be more impactful on child hyperactivity than prenatal smoke exposure,” they wrote. “This level of activity was present in academic settings and did not confer advantages for managing BMI.”

Overall, the team concluded that smoking after birth continues to be a risk factor for hyperactivity and ADHD in such children.

The study, “Objective Measurements Demonstrate Secondhand Rather than Prenatal Smoke Exposure is Related to Children’s Hyperactivity,” was presented at APSARD 2021.