Council on Environmental Health
Article Review

Prepared by: Mark A. Anderson, MD, MPH
February 2010

TITLE
Prenatal and Postnatal Tobacco Exposure and Behavioral Problems in 10-year-old Children: Results from the GINI-plus Prospective Birth Cohort Study

AUTHORS
Rückinger S, Rzehak P, Chen C-M, Sausenthaler S, Koletzko S, Bauer C-P, et al. 

FIND IT AT
Environmental Health Perspectives, January 2010, 118(1): 150-154
http://ehp03.niehs.nih.gov/article/fetchArticle.action?articleURI=info%3Adoi%2F10.1289%2Fehp.0901209

THE PROBLEM
Exposure of children to tobacco smoke, both prenatally and in utero, is a well-known risk factor for adverse health outcomes. Although prenatal and postnatal tobacco exposure have been reported to be associated with behavioral problems, associations with exposures at specific times or periods have not been established. For instance, delineating the impact of prenatal versus postnatal tobacco exposure has been challenging since children whose mothers smoked during pregnancy are likely to be exposed to tobacco smoke after birth.

WHAT THEY DID
The researchers analyzed data from a prospective birth cohort study undertaken in two cities in Germany. The sample included 5991 children born between 1995 and 1998 as well as their parents. Investigators measured behavioral problems using the Strengths and Difficulties Questionnaire (SDQ) 10 years after the birth of the child. Exposure was assessed at birth and the periodic follow-up interviews (at least 5 per subject), and behavioral problems were identified based on parental responses to the SDQ questionnaire. Children were classified as normal, borderline or abnormal for emotional symptoms, conduct problems, hyperactivity/inattention, peer-relationship problems, and total difficulties according to standard SDQ cut points.

WHAT THEY FOUND
Compared with children not exposed to tobacco smoke, children exposed both pre- and postnatally to tobacco smoke had twice the estimated risk of being classified as abnormal according to the total difficulties score of the SDQ at 10 years of age. Children who were only exposed prenatally have a 90% higher risk while children who were only exposed postnatally had a 30% higher risk of behavioral difficulties. The authors also found a potential dose effect by comparing children of mothers who smoked heavily (>5 cigarettes/day) during pregnancy with children of mothers who smoked lightly (<5 cigarettes/day) during pregnancy and children who had never been exposed to tobacco smoke. Children with heavy prenatal tobacco smoke exposure had consistently higher risks of abnormal behavior than children with light exposure and children with no exposure. These results were found after adjusting for the potential cofounders of parental education, fathers employment, child’s time spent in front of computer or television screen, being a single father or mother, or mother’s age. However, missing from these analyses are important covariates that may be important in child behavior disorders: parental psychological problems; parenting variables (e.g., warmth, hostility); family climate factors (e.g., stressors, conflict in the home); and child health factors (e.g., birth weight, other illnesses).

DISCUSSION
The authors conclude that their findings support an association between behavioral problems and tobacco smoke exposure in school-age children. In particular, the authors conclude that, despite the potential influence of postnatal exposure, prenatal tobacco smoke exposure seems to be more important.  However, one should be cautious with interpretations of this study because of the potential for the omitted variables to impact study findings.

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