Peter Baghurst

Low-Level Environmental Lead Exposure and Children's Intellectual Function: An International Pooled Analysis

Lead is a confirmed neurotoxin, but questions remain about lead-associated intellectual deficits at blood lead levels < 10 μg/dL and whether lower exposures are, for a given change in exposure, associated with greater deficits. The objective of this study was to examine the association of intelligence test scores and blood lead concentration, especially for children who had maximal measured blood lead levels < 10 μg/dL. We examined data collected from 1,333 children who participated in seven international population-based longitudinal cohort studies, followed from birth or infancy until 5–10 years of age. The full-scale IQ score was the primary outcome measure. The geometric mean blood lead concentration of the children peaked at 17.8 μg/dL and declined to 9.4 μg/dL by 5–7 years of age; 244 (18%) children had a maximal blood lead concentration < 10 μg/dL, and 103 (8%) had a maximal blood lead concentration < 7.5 μg/dL. After adjustment for covariates, we found an inverse relationship between blood lead concentration and IQ score. Using a log-linear model, we found a 6.9 IQ point decrement [95% confidence interval (CI), 4.2–9.4] associated with an increase in concurrent blood lead levels from 2.4 to 30 μg/dL. The estimated IQ point decrements associated with an increase in blood lead from 2.4 to 10 μg/dL, 10 to 20 μg/dL, and 20 to 30 μg/dL were 3.9 (95% CI, 2.4–5.3), 1.9 (95% CI, 1.2–2.6), and 1.1 (95% CI, 0.7–1.5), respectively. For a given increase in blood lead, the lead-associated intellectual decrement for children with a maximal blood lead level < 7.5 μg/dL was significantly greater than that observed for those with a maximal blood lead level ≥7.5 μg/dL (p = 0.015). We conclude that environmental lead exposure in children who have maximal blood lead levels < 7.5 μg/dL is associated with intellectual deficits.

The mental health of young people in Australia: key findings from the child and adolescent component of the national survey of mental health and well-being

Objective: To identify the prevalence of three mental disorders (Depressive Disorder, Conduct Disorder and Attention-Deficit/Hyperactivity Disorder), the prevalence of mental health problems, the health-related quality of life of those with problems, and patterns of service utilisation of those with and without mental health problems, among 4–17-year-olds in Australia. To identify rates of health-risk behaviours among adolescents with mental health problems. Method: The mental disorders were assessed using the parent-version of the Diagnostic Interview Schedule for Children Version IV. Parents completed the Child Behaviour Checklist to identify mental health problems and standard questionnaires to assess healthrelated quality of life and service use. The Youth Risk Behaviour Questionnaire completed by adolescents was employed to identify health-risk behaviours. Results: Fourteen percent of children and adolescents were identified as having mental health problems. Many of those with mental health problems had problems in other areas of their lives and were at increased risk for suicidal behaviour. Only 25%% of those with mental health problems had attended a professional service during the six months prior to the survey. Conclusion: Child and adolescent mental health problems are an important public health problem in Australia. The appropriate balance between funding provided for clinical interventions focusing on individual children and families and funding for interventions that focus on populations, requires careful study. The latter are an essential component of any strategy to reduce mental health problems as the high prevalence of problems makes it unlikely that individual care will ever be available for all those needing help. Clinical and population health interventions must take into account the comorbid problems experienced by children with mental disorders.

Port Pirie Cohort Study: Environmental Exposure to Lead and Children's Abilities at the Age of Four Years

We studied the effect of environmental exposure to lead on childrens abilities at the age of four years in a cohort of 537 children born during 1979 to 1982 to women living in a community situated near a lead smelter. Samples for measuring blood lead levels were obtained from the mothers antenatally, at delivery from the mothers and umbilical cords, and at the ages of 6, 15, and 24 months and then annually from the children. Concurrently, the mothers were interviewed about personal, family, medical, and environmental factors. Maternal intelligence, the home environment, and the childrens mental development (as evaluated with use of the McCarthy Scales of Childrens Abilities) were formally assessed. The mean blood lead concentration varied from 0.44 mumol per liter in midpregnancy to a peak of 1.03 mumol per liter at the age of two years. The blood lead concentration at each age, particularly at two and three years, and the integrated postnatal average concentration were inversely related to development at the age of four. Multivariate analysis incorporating many factors in the childrens lives indicated that the subjects with an average postnatal blood lead concentration of 1.50 mumol per liter had a general cognitive score 7.2 points lower (95 percent confidence interval, 0.3 to 13.2; mean score, 107.1) than those with an average concentration of 0.50 mumol per liter. Similar deficits occurred in the perceptual-performance and memory scores. Within the range of exposure studied, no threshold dose for an effect of lead was evident. We conclude that postnatal blood lead concentration is inversely related to cognitive development in children, although one must be circumspect in making causal inferences from studies of this relation, because of the difficulties in defining and controlling confounding effects.

Environmental lead and children's intelligence : a systematic review of the epidemiological evidence

Abstract Objective: To quantify the magnitude of the relation between full scale IQ in children aged 5 or more and their body burden of lead. Design: A systematic review of 26 epidemiological studies since 1979: prospective studies of birth cohorts, cross sectional studies of blood lead, and cross sectional studies of tooth lead. Setting: General populations of children >=5 years. Main outcome measures - For each study, the regression coefficient of IQ on lead, after adjustment for confounders when possible, was used to derive the estimated change in IQ for a specific doubling of either blood or tooth lead. Results: The five prospective studies with over 1100 children showed no association of cord blood lead or antenatal maternal blood lead with subsequent IQ. Blood lead at around age 2 had a small and significant inverse association with IQ, somewhat greater than that for mean blood lead over the preschool years. The 14 cross sectional studies of blood lead with 3499 children showed a significant inverse association overall, but showed more variation in their results and their ability to allow for confounders. The seven cross sectional studies of tooth lead with 2095 children were more consistent in finding an inverse association, although the estimated magnitude was somewhat smaller. Overall synthesis of this evidence, including a meta-analysis, indicates that a typical doubling of body lead burden (from 10 to 20 μg/dl (0.48 to 0.97 μmol/l) blood lead or from 5 to 10 μg/g tooth lead) is associated with a mean deficit in full scale IQ of around 1-2 IQ points. Conclusion: While low level lead exposure may cause a small IQ deficit, other explanations need considering: are the published studies representative; is there inadequate allowance for confounders; are there selection biases in recruiting and following children; and do children of lower IQ adopt behaviour which makes them more prone to lead uptake (reverse causality)? Even if moderate increases in body lead burden adversely affect IQ, a threshold below which there is negligible influence cannot currently be determined. Because of these uncertainties, the degree of public health priority that should be devoted to detecting and reducing moderate increases in childrens blood lead, compared with other important social detriments that impede childrens development, needs careful consideration.

Validity of DSM-IV ADHD Subtypes in a Nationally Representative Sample of Australian Children and Adolescents

ABSTRACT Objective To examine the discriminant validity of DSM-IV attention-deficit/hyperactivity disorder (ADHD) subtypes in a nationally representative sample of Australian youths. Method The Diagnostic Interview Schedule for Children, including the symptom-specific impairment questions, was administered to 3,597 parents of children aged 6 to 17 years (response rate=70%). Parents also completed questionnaires assessing childrens emotional and behavioral problems and quality of life. Results Current DSM-IV ADHD prevalence was 7.5% (6.8% with impairment) with inattentive types being more common than hyperactive-impulsive and combined types. ADHD was more prevalent among young males and was linked to social adversity, particularly for combined types. Compared with non-ADHD controls, all three ADHD subtypes were rated as having more emotional and behavioral problems and lower psychosocial quality of life, with combined types consistently rated the most impaired. Combined types received higher ratings than hyperactive-impulsive and inattentive types on externalizing behavior problems, disruption to family activities, and symptom-specific impairments with schoolwork and peer-related activities. Inattentive types were rated as having lower self-esteem, more social and school-related problems, but fewer externalizing problems than hyperactive-impulsive types. Conclusion These findings support the view of DSM-IV ADHD subtypes as distinct clinical entities with impairments in multiple domains.

Health-Related Quality of Life of Children and Adolescents With Mental Disorders

OBJECTIVE To compare the health-related quality of life (HRQL) between children aged 6-17 years with one of three mental disorders (attention-deficit/hyperactivity disorder, major depressive disorder, or conduct disorder), a physical disorder, and those with none of these disorders. METHOD Parent reports describing the HRQL, mental disorders, and physical disorders of a national sample of 3,597 children and adolescents in Australia, aged 6-17 years (response rate = 70%), were obtained by means of a structured diagnostic interview and questionnaires. RESULTS After controlling for age, gender, and family structure, children with mental disorders were reported to have a significantly worse HRQL in several domains than children with no disorder. In many areas they were reported to have a worse HRQL than children with physical disorders. Parents also reported that the problems of children with mental disorders interfered significantly with the daily lives of children, parents, and families. CONCLUSIONS The findings are consistent with previous studies which have reported that adults with mental disorders have substantial impairment in their HRQL. The findings suggest that children with a mental disorder require help in many areas of their lives. Achieving this will require an integrated approach to health care delivery rather than the current distinction between physical and mental health services.

Lifetime exposure to environmental lead and children's intelligence at 11-13 years: the Port Pirie cohort study

Abstract Objective: To examine the association between environmental exposure to lead and childrens intelligence at age 11-13 years, and to assess the implications of exposure in the first seven years of life for later childhood development. Design: Prospective cohort study. Subjects: 375 children born in or around the lead smelting town of Port Pirie, Australia, between 1979 and 1982. Main outcome measure: Childrens intelligence quotient (IQ) measured at 11-13 years of age. Results: IQ was inversely associated with both antenatal and postnatal blood lead concentrations. Verbal, performance, and full scale IQ were inversely related to blood lead concentration with no apparent threshold. Multivariate analyses indicated that after adjustment for a wide range of confounders, the postnatal blood lead concentrations (particularly within the age range 15 months to 7 years) exhibited inverse associations with IQ. Strong associations with IQ were observed for lifetime average blood lead concentrations at various ages. The expected mean full scale IQ declined by 3.0 points (95% confidence interval 0.07 to 5.93) for an increase in lifetime average blood lead concentration from 0.48 to 0.96 µmol/l (10 to 20 µg/dl). Conclusions: Exposure to environmental lead during the first seven years of life is associated with cognitive deficits that seem to persist into later childhood. Key messages Few longitudinal data have yet been reported on the time course of the effects of exposure to environmental lead Exposure to environmental lead early in life is associated with cognitive deficits that persist into middle childhood The duration, intensity, and timing of exposure to lead, as well as other social and familial factors, may influence the nature and degree of reversibility The formulation of a public health policy for preventing any possible effects of lead exposure should be based on a composite consideration of the childs health and the best use of existing resources

Childhood cancer: a 4-year prospective study of the psychological adjustment of children and parents.

PURPOSE The objective of this 4-year prospective study was to assess the psychological adjustment of children treated for cancer and their parents. PATIENTS AND METHODS Children aged 2 to 12 years with cancer diagnosed and their parents and families (n = 39) were assessed immediately after their diagnosis and then annually for the next 4 years. At each assessment, the psychological adjustment of the children and their families was compared with the adjustment of a cohort of children and families in the general community (n = 49). RESULTS Immediately after the diagnosis of cancer in the children, the children and their parents had significantly more psychological problems than children and parents in the community. However, at subsequent assessments, there was no difference in the number of psychological problems experienced by children and parents in the two groups. CONCLUSIONS In the longer term, the prevalence of psychological problems experienced by children treated for cancer and their parents does not differ from that found in children and parents in the general community. Future research should give greater attention to other aspects of the lives of children treated for cancer and their parents, including their broader health-related quality of life.

Effect of Treatment of Gestational Diabetes Mellitus on Obesity in the Next Generation

OBJECTIVE Gestational diabetes mellitus (GDM) may cause obesity in the offspring. The objective was to assess the effect of treatment for mild GDM on the BMI of 4- to 5-year-old children. RESEARCH DESIGN AND METHODS Participants were 199 mothers who participated in a randomized controlled trial of the treatment of mild GDM during pregnancy and their children. Trained nurses measured the height and weight of the children at preschool visits in a state-wide surveillance program in the state of South Australia. The main outcome measure was age- and sex-specific BMI Z score based on standards of the International Obesity Task Force. RESULTS At birth, prevalence of macrosomia (birth weight ≥4,000 g) was 5.3% among the 94 children whose mothers were in the intervention group, and 21.9% among the 105 children in the routine care control group. At 4- to 5-years-old, mean (SD) BMI Z score was 0.49 (1.20) in intervention children and 0.41 (1.40) among controls. The difference between treatment groups was 0.08 (95% CI −0.29 to 0.44), an estimate minimally changed by adjustment for maternal race, parity, age, and socio-economic index (0.08 [−0.29 to 0.45]). Evaluating BMI ≥85th percentile rather than continuous BMI Z score gave similarly null results. CONCLUSIONS Although treatment of GDM substantially reduced macrosomia at birth, it did not result in a change in BMI at age 4- to 5-years-old.

Cigarette smoking and pancreatic cancer: an analysis from the International Pancreatic Cancer Case-Control Consortium (Panc4)

BACKGROUND To evaluate the dose-response relationship between cigarette smoking and pancreatic cancer and to examine the effects of temporal variables. METHODS We analyzed data from 12 case-control studies within the International Pancreatic Cancer Case-Control Consortium (PanC4), including 6507 pancreatic cases and 12 890 controls. We estimated summary odds ratios (ORs) by pooling study-specific ORs using random-effects models. RESULTS Compared with never smokers, the OR was 1.2 (95% confidence interval [CI] 1.0-1.3) for former smokers and 2.2 (95% CI 1.7-2.8) for current cigarette smokers, with a significant increasing trend in risk with increasing number of cigarettes among current smokers (OR=3.4 for ≥35 cigarettes per day, P for trend<0.0001). Risk increased in relation to duration of cigarette smoking up to 40 years of smoking (OR=2.4). No trend in risk was observed for age at starting cigarette smoking, whereas risk decreased with increasing time since cigarette cessation, the OR being 0.98 after 20 years. CONCLUSIONS This uniquely large pooled analysis confirms that current cigarette smoking is associated with a twofold increased risk of pancreatic cancer and that the risk increases with the number of cigarettes smoked and duration of smoking. Risk of pancreatic cancer reaches the level of never smokers ∼20 years after quitting.