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Children who started using tobacco by age 10 had significantly inferior cognitive performance and smaller brain structures after a 2-year follow-up period, a cohort study reported.

Those reporting ever using tobacco products had significantly lower scores in the Picture Vocabulary Test of the NIH Toolbox Cognition Battery both at baseline and at 2-year follow-up compared with never-users, according to findings in .

Crystallized cognition composite scores were also significantly lower among ever-users at baseline and at 2-year follow-up.

Furthermore, structural MRI revealed that whole-brain measures in cortical areas were significantly lower among ever-users at baseline, whereas cortical volumes were reduced in ever-users at baseline and at 2 years, reported Hongying Daisy Dai, PhD, of University of Nebraska Medical Center in Omaha, and colleagues.

The researchers also found other reduced areas and volumes across multiple frontal, parietal, and temporal lobes among ever-users of tobacco.

These results may be clinically important, as childhood to early adolescence is a critical period of brain development.

More adolescents are using electronic cigarettes and other non-cigarette tobacco products, with e-cigarettes surpassing cigarettes as the most used tobacco product by youths in 2014, the authors noted. They cited that in 2020, 19.6% of high school students reported using e-cigarettes in the past 30 days.

"The risks of childhood nicotine exposure for long-term cognitive outcomes extend beyond self-administration," Steven R. Laviolette, PhD, of University of Western Ontario, Canada, pointed out in an .

He cited prior evidence for a link between childhood exposure to parental secondhand smoke and deficits in midlife episodic memory function and associative learning, along with impairments in short-term and spatial working memory.

"[I]t is well-established that nicotine dependence is highly comorbid with a wide range of neuropsychiatric disorders, including mood and anxiety disorders, schizophrenia, and other substance use disorders such as alcohol and cannabis use, although the mechanistic associations between these comorbidities are poorly understood," Laviolette said.

"Together, this emerging evidence from both preclinical and clinical studies underscores the neurotoxic effects of nicotine exposure during sensitive periods of brain development and highlights the ability of nicotine to pathologically interfere with a host of neurochemical, morphological, and molecular pathways critical to healthy cognitive outcomes and long-term mental health," he concluded.

This observational cohort study was conducted using data from the (ABCD) study of children 9 to 10 years old at 21 U.S. sites.

Data from 11,729 participants (mean age 9.9 years, 52.1% boys, 52.1% non-Hispanic white) were collected from October 2016 to October 2018 with a 2-year follow-up. Findings were adjusted for age, sex assigned at birth, race and ethnicity, ever use of other substances, youth pubertal stage, parent monitoring, and school environment.

Ever-use of tobacco was assessed by questions about e-cigarettes, cigarettes, cigars, smokeless tobacco, hookah, pipe, and nicotine replacement use. Participants responding affirmatively to any of these questions were classified as ever-users.

Dai's group acknowledged that ABCD study participants may not be fully nationally representative. Tobacco use was self-reported and may be subject to social desirability bias, especially for youths. Causal inference also cannot be established based on the data in this study.

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