Robert S. Kahn

Exposures to environmental toxicants and attention deficit hyperactivity disorder in U.S. children

Objective The purpose of this study was to examine the association of exposures to tobacco smoke and environmental lead with attention deficit hyperactivity disorder (ADHD). Methods Data were obtained from the National Health and Nutrition Examination Survey 1999–2002. Prenatal and postnatal tobacco exposure was based on parent report; lead exposure was measured using blood lead concentration. ADHD was defined as having current stimulant medication use and parent report of ADHD diagnosed by a doctor or health professional. Results Of 4,704 children 4–15 years of age, 4.2% were reported to have ADHD and stimulant medication use, equivalent to 1.8 million children in the United States. In multivariable analysis, prenatal tobacco exposure [odds ratio (OR) = 2.5; 95% confidence interval (CI), 1.2–5.2] and higher blood lead concentration (first vs. fifth quintile, OR = 4.1; 95% CI, 1.2–14.0) were significantly associated with ADHD. Postnatal tobacco smoke exposure was not associated with ADHD (OR = 0.6; 95% CI, 0.3–1.3; p = 0.22). If causally linked, these data suggest that prenatal tobacco exposure accounts for 270,000 excess cases of ADHD, and lead exposure accounts for 290,000 excess cases of ADHD in U.S. children. Conclusions We conclude that exposure to prenatal tobacco and environmental lead are risk factors for ADHD in U.S. children.

State income inequality, household income, and maternal mental and physical health: cross sectional national survey.

Abstract Objective: To examine the association of state income inequality and individual household income with the mental and physical health of women with young children. Design: Cross sectional study. Individual level data (outcomes, income, and other sociodemographic covariates) from a 1991 follow up survey of a birth cohort established in 1988. State level income inequality calculated from the income distribution of each state from 1990 US census. Setting: United States, 1991. Participants: Nationally representative stratified random sample of 8060 women who gave birth in 1988 and were successfully contacted (89%) in 1991. Main outcome measures: Depressive symptoms (Center for Epidemiologic Studies depression score >15) and self rated health Results: 19% of women reported depressive symptoms, and 7.5% reported fair or poor health. Compared with women in the highest fifth of distribution of household income, women in the lowest fifth were more likely to report depressive symptoms (33% v 9%, P<0.001) and fair or poor health (15% v 2%, P<0.001). Compared with low income women in states with low income inequality, low income women in states with high income inequality had a higher risk of depressive symptoms (odds ratio 1.6, 95% confidence interval 1.0 to 2.6) and fair or poor health (1.8, 0.9 to 3.5). Conclusions: High income inequality confers an increased risk of poor mental and physical health, particularly among the poorest women. Both income inequality and household income are important for health in this population.

Patterns of Comorbidity, Functioning, and Service Use for US Children With ADHD, 2007

OBJECTIVE: To determine patterns of comorbidity, functioning, and service use for US children with attention-deficit/hyperactivity disorder (ADHD). METHODS: Bivariate and multivariable cross-sectional analyses were conducted on data from the 2007 National Survey of Childrens Health on 61 779 children ages 6 to 17 years, including 5028 with ADHD. RESULTS: Parent-reported diagnosed prevalence of ADHD was 8.2%. Children with ADHD were more likely to have other mental health and neurodevelopmental conditions. Parents reported that 46% of children with ADHD had a learning disability versus 5% without ADHD, 27% vs 2% had a conduct disorder, 18% vs 2% anxiety, 14% vs 1% depression, and 12% vs 3% speech problems (all P < .05). Most children with ADHD had at least 1 comorbid disorder: 33% had 1, 16% had 2, and 18% had 3 or more. The risk for having 3 or more comorbidities was 3.8 times higher for poor versus affluent children (30% vs 8%). Children with ADHD had higher odds of activity restriction (odds ratio: 4.14 [95% confidence interval: 3.34–5.15]), school problems (odds ratio: 5.18 [95% confidence interval: 4.47–6.01]), grade repetition, and poor parent-child communication, whereas social competence scores were lower and parent aggravation higher. Functioning declined in a stepwise fashion with increasing numbers of comorbidities, and use of health and educational services and need for care coordination increased. CONCLUSIONS: Clinical management of ADHD must address multiple comorbid conditions and manage a range of adverse functional outcomes. Therapeutic approaches should be responsive to each childs neurodevelopmental profile, tailored to their unique social and family circumstances, and integrated with educational, mental health and social support services.

A Reexamination of Smoking Before, During, and After Pregnancy

OBJECTIVES This study examined the patterns and correlates of maternal smoking before, during, and after pregnancy. METHODS We examined socioeconomic, demographic, and clinical risk factors associated with maternal smoking in a nationally representative cohort of women (n = 8285) who were surveyed 17 +/- 5 months and again 35 +/- 5 months after delivery. RESULTS Smoking rates among women with a college degree decreased 30% from before pregnancy to 35 months postpartum but did not change among the least educated women. Risk factors clustered, and a gradient linked the number of risk factors (0, 2, 4) to the percentage smoking (6%, 31%, 58%, P <.0001). CONCLUSIONS The period of pregnancy and early parenthood is associated with worsening education-related disparities in smoking as well as substantial clustering of risk factors. These observations could influence the targeting and design of maternal smoking interventions.

Association of tobacco and lead exposures with attention-deficit/hyperactivity disorder.

OBJECTIVE: The study objective was to determine the independent and joint associations of prenatal tobacco and childhood lead exposures with attention-deficit/hyperactivity disorder (ADHD), as defined by current diagnostic criteria, in a national sample of US children. METHODS: Data are from the 2001–2004 National Health and Nutrition Examination Survey, a cross-sectional, nationally representative sample of the US population. Participants were 8 to 15 years of age (N = 2588). Prenatal tobacco exposure was measured by report of maternal cigarette use during pregnancy. Lead exposure was assessed by using current blood lead levels. The Diagnostic Interview Schedule for Children was used to ascertain the presence of ADHD in the past year, on the basis of Diagnostic and Statistical Manual of Mental Disorders, Fourth Edition, criteria. RESULTS: A total of 8.7% (95% confidence interval [CI]: 7.3%–10.1%) of children met criteria for ADHD. Prenatal tobacco exposure (adjusted odds ratio [aOR]: 2.4 [95% CI: 1.5–3.7]) and higher current blood lead concentrations (aOR for third versus first tertile: 2.3 [95% CI: 1.5–3.8]) were independently associated with ADHD. Compared with children with neither exposure, children with both exposures (prenatal tobacco exposure and third-tertile lead levels) had an even greater risk of ADHD (aOR: 8.1 [95% CI: 3.5–18.7]) than would be expected if the independent risks were multiplied (tobacco-lead exposure interaction term, P < .001). CONCLUSIONS: Prenatal tobacco and childhood lead exposures are associated with ADHD in US children, especially among those with both exposures. Reduction of these common toxicant exposures may be an important avenue for ADHD prevention.

Rethinking race/ethnicity, income, and childhood asthma: racial/ethnic disparities concentrated among the very poor.

Objective. Past studies of the prevalence of childhood asthma have yielded conflicting findings as to whether racial/ethnic disparities remain after other factors, such as income, are taken into account. The objective of this study was to examine the association of race/ethnicity and family income with the prevalence of childhood asthma and to assess whether racial/ethnic disparities vary by income strata. Methods. Cross-sectional data on 14,244 children aged <18 years old in the 1997 National Health Interview Survey were examined. The authors used logistic regression to analyze the independent and joint effects of race/ethnicity and income-to-federal poverty level (FPL) ratio, adjusting for demographic covariates. The main outcome measure was parental report of the child having ever been diagnosed with asthma. Results. Bivariate analyses, based on weighted percentages, revealed that asthma was more prevalent among non-Hispanic black children (13.6%) than among non-Hispanic white children (11.2%; p<0.01), but the prevalence of asthma did not differ significantly between Hispanic children (10.1 %) and non-Hispanic white children (11.2%; p=0.13). Overall, non-Hispanic black children were at higher risk for asthma than non-Hispanic white children (adjusted odds ratio [OR] = 1.20; 95% confidence interval [CI] 1.03, 1.40), after adjustment for sociodemographic variables, including the ratio of annual family income to the FPL. Asthma prevalence did not differ between Hispanic children and non-Hispanic white children in adjusted analyses (adjusted OR=0.85; 95% CI 0.71, 1.02). Analyses stratified by income revealed that only among children from families with incomes less than half the FPL did non-Hispanic black children have a higher risk of asthma than non-Hispanic white children (adjusted OR=1.99; 95% CI 1.09, 3.64). No black vs. white differences existed at other income levels. Subsequent analyses of these very poor children that took into account additional potentially explanatory variables did not attenuate the higher asthma risk for very poor non-Hispanic black children relative to very poor non-Hispanic white children. Conclusions. Non-Hispanic black children were at substantially higher risk of asthma than non-Hispanic white children only among the very poor. The concentration of racial/ethnic differences only among the very poor suggests that patterns of social and environmental exposures must overshadow any hypothetical genetic risk.

Women's Health After Pregnancy and Child Outcomes at Age 3 Years: A Prospective Cohort Study

OBJECTIVES This study examined the persistence and comorbidity of womens physical and mental health conditions after pregnancy and the association of these conditions with child outcomes. METHODS A national cohort of women who recently gave birth were surveyed in 1988 and again in 1991. We examined longitudinal data on maternal poor physical health, depressive symptoms, and smoking, and maternal report of child outcomes (at age approximately 3 years). RESULTS Womens poor physical health and smoking had strong, graded associations with childrens physical health and behavior problems, whereas womens depressive symptoms were associated with childrens delayed language and behavior problems. CONCLUSIONS Substantial persistence and comorbidity of womens health conditions exist after pregnancy with adverse effects on early child outcomes. Child health professionals should support services and policies that promote womens health outside the context of pregnancy.

Prenatal Exposure to Bisphenol A and Child Wheeze from Birth to 3 Years of Age

Background: Bisphenol A (BPA), an endocrine-disrupting chemical that is routinely detected in > 90% of Americans, promotes experimental asthma in mice. The association of prenatal BPA exposure and wheeze has not been evaluated in humans. Objective: We examined the relationship between prenatal BPA exposure and wheeze in early childhood. Methods: We measured BPA concentrations in serial maternal urine samples from a prospective birth cohort of 398 mother–infant pairs and assessed parent-reported child wheeze every 6 months for 3 years. We used generalized estimating equations with a logit link to evaluate the association of prenatal urinary BPA concentration with the dichotomous outcome wheeze (wheeze over the previous 6 months). Results: Data were available for 365 children; BPA was detected in 99% of maternal urine samples during pregnancy. In multivariable analysis, a one-unit increase in log-transformed creatinine-standardized mean prenatal urinary BPA concentration was not significantly associated with child wheeze from birth to 3 years of age, but there was an interaction of BPA concentration with time (p = 0.003). Mean prenatal BPA above versus below the median was positively associated with wheeze at 6 months of age [adjusted odds ratio (AOR) = 2.3; 95% confidence interval (CI): 1.3, 4.1] but not at 3 years (AOR = 0.6; 95% CI: 0.3, 1.1). In secondary analyses evaluating associations of each prenatal BPA concentration separately, urinary BPA concentrations measured at 16 weeks gestation were associated with wheeze (AOR = 1.2; 95% CI: 1.0, 1.5), but BPA concentrations at 26 weeks of gestation or at birth were not. Conclusions: Mean prenatal BPA was associated with increased odds of wheeze in early life, and the effect diminished over time. Evaluating exposure at each prenatal time point demonstrated an association between wheeze from 6 months to 3 years and log-transformed BPA concentration at 16 weeks gestation only.

Role of Financial and Social Hardships in Asthma Racial Disparities

BACKGROUND AND OBJECTIVES: Health care reform offers a new opportunity to address child health disparities. This study sought to characterize racial differences in pediatric asthma readmissions with a focus on the potential explanatory role of hardships that might be addressed in future patient care models. METHODS: We enrolled 774 children, aged 1 to 16 years, admitted for asthma or bronchodilator-responsive wheezing in a population-based prospective observational cohort. The outcome was time to readmission. Child race, socioeconomic status (measured by lower income and caregiver educational attainment), and hardship (caregivers looking for work, having no one to borrow money from, not owning a car or home, and being single/never married) were recorded. Analyses used Cox proportional hazards. RESULTS: The cohort was 57% African American, 33% white, and 10% multiracial/other; 19% were readmitted within 12 months. After adjustment for asthma severity classification, African Americans were twice as likely to be readmitted as whites (hazard ratio: 1.98; 95% confidence interval: 1.42 to 2.77). Compared with whites, African American caregivers were significantly more likely to report lower income and educational attainment, difficulty finding work, having no one to borrow money from, not owning a car or home, and being single/never married (all P ≤ .01). Hardships explained 41% of the observed racial disparity in readmission; jointly, socioeconomic status and hardship explained 49%. CONCLUSIONS: African American children were twice as likely to be readmitted as white children; hardships explained >40% of this disparity. Additional factors (eg, pollution, tobacco exposure, housing quality) may explain residual disparities. Targeted interventions could help achieve greater child health equity.

Interactive Effects of a DRD4 Polymorphism, Lead, and Sex on Executive Functions in Children

BACKGROUND Prior studies have examined independent effects of a dopamine receptor D4 polymorphism (DRD4-7) and lead exposure on executive functions but not their interaction or the role of sex as a modifier of their effects. METHODS Multivariable analyses were used to examine effects of DRD4-7 genotype, 60-month blood lead level, and sex on spatial working memory, rule learning and reversal, spatial span, and planning for 174 children. RESULTS DRD4-7 was associated with poorer spatial working memory, and increasing blood lead levels were associated with impaired rule learning and reversal, spatial span, and planning. Adverse effects of lead on planning and rule learning and reversal were seen primarily for boys. In addition, the effect of lead on rule learning and reversal was evident predominately for those lacking DRD4-7. CONCLUSIONS We observed independent effects of DRD4-7 and lead on various executive functions and modifications of lead effects by DRD4 genotype and sex.