Prenatal and Postnatal Tobacco Exposure and Behavioral Problems in 10-year-old

From Environmental Health Perspectives
Children: Results from the GINI-plus Prospective Birth
Simon Rückinger; Peter Rzehak; Chih-Mei Chen; Stefanie Sausenthaler; Sibylle Koletzko; Carl-Peter Bauer; Ute Hoffmann; Ursula Kramer; Dietrich Berdel; Andrea von Berg; Otmar Bayer; H.-Erich Wichmann; Rüdiger von Kries; Joachim Heinrich

Posted: 02/18/2010; Environmental Health Perspectives. 2010;118(1):150-154. © 2010 National Institute of Environmental Health Sciences

Abstract
Background: Prenatal and postnatal tobacco exposure have been reported to be associated with behavioral problems. However, the magnitude of the association with tobacco exposure at specific periods of exposure is unclear.

Objective: We assessed the relative risk of behavioral problems in children who had been exposed to tobacco smoke in utero and postnatally.

Methods: We analyzed data from a prospective birth cohort study in two cities in Germany: the German Infant Nutrition Intervention. Our sample included 5,991 children born between 1995 and 1998 as well as their parents. We measured behavioral problems using the Strength and Difficulties Questionnaire (SDQ) at follow-up 10 years after birth. According to prespecified SDQ cutoff values, children were classified as "normal," "borderline," or "abnormal" according to the subscales "emotional symptoms," "conduct problems," "hyperactivity/inattention," "peer-relationship problems," and a total difficulties score. Smoke exposure and further covariates were assessed using parent

Results: Compared with children not exposed to tobacco smoke, children exposed both pre- and postnatally to tobacco smoke had twice the estimated risk [95% confidence interval (CI), 1.4-3.1] of being classified as abnormal according to the total difficulties score of the SDQ at 10 years of age.

Children who were only prenatally exposed had a 90% higher relative risk (95% CI, 0.9-4.0), whereas children who were only postnatally exposed had a 30% higher relative risk (95% CI, 0.9-1.9).
These results could not be explained by confounding by parental education, father's employment, child's time spent in front of computer or television screen, being a single father or mother, or mother's age.

Conclusions: Prenatal exposure to tobacco smoke is associated with behavioral problems in school-age children.
Although our findings do not preclude the influence of postnatal exposure, prenatal exposure seems to be more important.

Introduction
Exposure of children to tobacco smoke, whether postnatal or in utero, is a well-known risk factor for various adverse health outcomes (DiFranza et al. 2004).

An increased risk for intrauterine growth retardation, sudden infant death syndrome, and asthma are well-known adverse effects of in utero tobacco exposure (Higgins 2002).
In addition, effects of in utero tobacco exposure on behavioral problems have been reported in various experimental and epidemiologic studies (Ernst et al. 2001; Eskenazi and Castorina 1999; Wakschlag et al. 2002; Weitzman et al. 2002) including some longitudinal studies (Markussen Linnet et al. 2006; Wakschlag et al. 1997). Prospective studies that systematically assess a broad range of behavioral problems outcomes are sparse.

Many studies have found an association between smoking in pregnancy and behavioral problems among children (Batstra et al. 2003; Roza et al. 2009; Saxton 1978).

An independent effect of postnatal tobacco exposure on behavioral development has also been suggested (Braun et al. 2006, 2008; Fergusson et al. 1993; Weitzman et al. 1992; Williams et al. 1998). However, specifically delineating the impact of prenatal versus postnatal tobacco exposure is a challenging task: Children whose mothers have smoked during pregnancy are likely to be exposed to tobacco smoke after birth. Furthermore, many studies use cross-sectional designs where recall bias may play an important role. The specific roles of pre- and postnatal exposure are not yet clarified.

In this study, we analyzed data from the German Infant Nutritional Intervention (GINI), a large prospective birth cohort that also contains comprehensive follow-up. GINI's prospective design and the comprehensive questions on tobacco smoke exposure at various time points provide the opportunity to disentangle the impacts of prenatal and postnatal tobacco exposure on behavioral problems. In a subset of this study, Gehring et al. (2006) tested the validity of the questionnaire-derived data on environmental tobacco smoke by measuring air nicotine and urine cotinine; the misclassification rate was below 7%, which is in line with that of other similar studies. We measured behavioral problems using the Strength and Difficulties Questionnaire (SDQ) (Goodman 1997), which allows assessment of a broad range of behavioral problems.

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