Port Pirie Cohort Study Research Articles

Revised Intercultural Sensitivity Scales: Psychometric evidence and personality links

This study examined the long-term associations between childhood lead exposure, childhood trauma and adult substance use, and subclinical psychotic experiences (SPEs) in the Port Pirie Cohort Study. Adult participants were initially 402 (175 males, 227 females) 25–29 year-olds followed up from the Port Pirie Cohort Study that commenced in 1979 (55.6% of the original cohort). Multiple linear regression analyses were conducted on a sub-sample of 158 participants for which adequate data was available. Variables examined as correlates of positive, negative and depressive SPEs included socioeconomic status at birth, cumulative blood lead level at age 7, maternal mental health, family functioning and cognitive ability at age 11-13, and adverse childhood experiences, alcohol use and cannabis use assessed during adulthood. Cumulative blood lead levels at age 7 were bi-variately associated with the frequency of positive SPEs in adulthood; however this relationship was not significant when other variables were accounted for. Adverse childhood experiences and substance use (cannabis use in particular) were significant correlates of SPEs in adulthood.

Childhood lead exposure, childhood trauma, substance use and subclinical psychotic experiences–a longitudinal cohort study

This study examined the long-term associations between childhood lead exposure, childhood trauma and adult substance use, and subclinical psychotic experiences (SPEs) in the Port Pirie Cohort Study. Adult participants were initially 402 (175 males, 227 females) 25–29 year-olds followed up from the Port Pirie Cohort Study that commenced in 1979 (55.6% of the original cohort). Multiple linear regression analyses were conducted on a sub-sample of 158 participants for which adequate data was available. Variables examined as correlates of positive, negative and depressive SPEs included socioeconomic status at birth, cumulative blood lead level at age 7, maternal mental health, family functioning and cognitive ability at age 11-13, and adverse childhood experiences, alcohol use and cannabis use assessed during adulthood. Cumulative blood lead levels at age 7 were bi-variately associated with the frequency of positive SPEs in adulthood; however this relationship was not significant when other variables were accounted for. Adverse childhood experiences and substance use (cannabis use in particular) were significant correlates of SPEs in adulthood.

Age 7 intelligence and paternal education appear best predictors of educational attainment: The Port Pirie Cohort Study

ObjectiveThe number of years of education an individual completes is related to their future morbidity and mortality. There are obvious drivers for educational attainment such as childhood intellect, parental intelligence and education attainment, as well as socioeconomic status; and associations may be age‐dependent. We investigated associations between intelligence across childhood (collected at two, four, seven and between eleven and thirteen years) and educational attainment (total years) by the late 20s in the Port Pirie Cohort Study, taking into account maternal intelligence, parental schooling and occupational prestige.MethodThere were 388 individuals from the population‐based longitudinal Port Pirie Cohort Study (South Australia) who provided educational attainment data in the 2008‐9 data collection wave. A Structural Equation Model was employed to test associations between educational attainment and childhood cognitive/IQ measures, taking into account parental factors of IQ, schooling and socioeconomic status.ResultsThe vast majority of variables displayed significant simple correlations with each other in expected directions, e.g. child cognitive/IQ measures with maternal IQ. In the full structural equation model, paternal schooling and child intelligence at seven years were the only variables significantly related to educational attainment by the late 20s; maternal intelligence was strongly associated with early life but not adolescent intelligence.ConclusionsThese findings highlight the complex inter‐generational transmission of social advantages, and substantiate the independent effects of education and intelligence on later morbidly and mortality.

Tracing the long-term legacy of childhood lead exposure: A review of three decades of the Port Pirie Cohort study

Several prospective cohort studies have demonstrated that childhood lead levels show small but statistically significant adjusted associations with subsequent development in later childhood and adolescence. The Port Pirie Cohort study is one of the few prospective cohort studies to follow participants into adulthood. This paper reviews all childhood and adulthood findings of the Port Pirie Cohort study to date.Cohort members (initially, 723 infants born in/around the lead-smelting town of Port Pirie) showed a wide range of childhood blood lead levels, which peaked around 2 years old (M=21.3μg/dL, SD=1.2). At all childhood assessments, postnatal lead levels – particularly those reflecting cumulative exposure – showed small significant associations with outcomes including cognitive development, IQ, and mental health problems. While associations were substantially attenuated after adjusting for several childhood covariates, many remained statistically significant. Furthermore, average childhood blood lead showed small significant associations with some adult mental health problems for females, including anxiety problems and phobia, though associations only approached significance following covariate adjustment. Overall, there did not appear to be any age of greatest vulnerability or threshold of effect, and at all ages, females appeared more susceptible to lead-associated deficits.Together, these findings suggest that the associations between early childhood lead exposure and subsequent developmental outcomes may persist. However, as the magnitude of these effects was small, they are not discernible at the individual level, posing more of a population health concern. It appears that the combination of multiple early childhood factors best predicts later development. As such, minimising lead exposure in combination with improving other important early childhood factors such as parent–child interactions may be the best way to improve developmental outcomes.

Prospective associations between childhood low-level lead exposure and adult mental health problems: The Port Pirie cohort study

Low-level environmental lead exposure during childhood is associated with poorer emotional/behavioural functioning in later childhood and adolescence. Scarce research has examined whether these apparent effects persist into adulthood. This study is the first to examine prospective associations between lead exposure across early childhood and several common adult mental health problems.Childhood data (including blood lead concentrations) and adult data (from mental health questionnaires and psychiatric interviews) were available for 210 participants (44% males, mean age=26.3 years) from the Port Pirie cohort study (1979–1982 birth cohort).Participants had a mean childhood (to 7 years) average blood lead concentration of 17.2μg/dL. Among females, childhood blood lead showed small significant positive associations with lifetime diagnoses of drug and alcohol abuse and social phobia, and with anxiety, somatic and antisocial personality problems. For example: for a 10μg/dL blood lead increase, females were 2.84 times (95% CI 1.10, 7.30) more likely to have an alcohol abuse diagnosis. However, adjustment for childhood covariates – particularly stimulation within the home environment – rendered these associations non-significant. No significant or sizeable unadjusted or adjusted associations were seen for males.The associations between early lead exposure and emotional/behavioural functioning in children might persist into adulthood, at least for females. However, it is unclear whether such results arise from residual confounding, or other mechanisms. Interventions that focus on improving the childhood home environment may have a long-term positive impact on adult mental health outcomes. However, more prospective research using large and representative samples is needed to substantiate these results.

The Conquest of Lead Poisoning: A Pyrrhic Victory

The Conquest of Lead Poisoning: A Pyrrhic Victory

Brain Injury in Congenital Heart Disease

Mortality rates for virtually all forms of congenital heart disease have declined with dramatic advances in medical, transcatheter, and surgical therapies. 1 As the population of congenital heart disease survivors has burgeoned, however, their long-term functional morbidities have become the focus of increasing concern. Among the foremost morbidities are adverse neurodevelopmental outcomes, with their profound personal and societal costs. 2 Article p 280 Neurological and developmental outcomes of congenital heart patients are influenced by many factors, both innate and acquired, with cumulative effects. Genetic syndromes such as trisomy 21 or 22q11 microdeletion3–5 may affect both the heart and the brain. Cerebral dysgenesis is reported to occur in 10% to 29% of children with congenital heart disease in autopsy series, with the incidence varying by lesion 6–8 ; findings may range from microdysgenesis to gross abnormalities such as agenesis of the corpus callosum, incomplete operculization, and microcephaly. During fetal life, congenital heart lesions may be associated with changes in cerebrovascular blood flow distribution and resistance. For example, fetuses with hypoplastic left heart syndrome, whose cerebral perfusion is supplied retrograde through the ductus arteriosus, have lower cerebrovascular resistance than normal. 9 Postnatal neurodevelopmental risk factors may derive from the sequelae of congenital heart disease itself—eg, chronic severe hypoxemia, failure to thrive, arrhythmias with cardiac arrest or hypotension—or from the procedures used for cardiac correction or palliation.10 Neuropathological studies have revealed both focal and diffuse infarction. Focal infarction has been ascribed to thromboembolic events, whereas a diffuse pattern of cerebral injury has been attributed to hypotension and hypoperfusion.11 More recent neuropathological data in infants who underwent reparative or palliative cardiac surgery reveals that not only are these children at increased risk of gray matter injury but also nascent white matter is at risk. For instance, in a series of infants who died after cardiac surgery, cerebral white matter damage (periventricular leukomalacia or diffuse white matter gliosis) was the most significant lesion in terms of severity and incidence. 12 Similarly, MRI performed in patients with congenital heart disease after surgery has revealed findings consistent with both gray matter injury and widely distributed white matter injury. 13 Risk factors for brain injury during infant heart surgery have been particularly well studied. Cardiopulmonary bypass carries the risks of particulate and gaseous microemboli, macroemboli, and hypoperfusion with accompanying diffuse ischemia/reperfusion injury. In neonates and infants undergoing surgery with use of hypothermic bypass techniques, the risk of brain injury may be influenced by perfusion variables such as the duration of total circulation arrest,14 the depth of hypothermia, 15 the rate and duration of core cooling, 16 pH management during core cooling (alpha-stat versus pH stat), 17,18 and the level of hemodilution. 19 Disruption of cerebral vasoregulation in the early postoperative period renders the brain more vulnerable to hemodynamic instability. 20–22 After infant heart surgery, longer length of stay in the intensive care unit or hospital is associated with worse neurodevelopmental outcome on mid-term follow-up. 23,24

Identification of Confounders in the Assessment of the Relationship between Lead Exposure and Child Development

PURPOSE: To explore the best approach to identify and adjust for confounders in epidemiologic practice. METHODS: In the Port Pirie cohort study, the selection of covariates was based on both a priori and an empirical consideration. In an assessment of the relationship between exposure to environmental lead and child development, change-in-estimate (CE) and significance testing (ST) criteria were compared in identifying potential confounders. The Pearson correlation coefficients were used to evaluate the potential for collinearity between pairs of major quantitative covariates. In multivariate analyses, the effects of confounding factors were assessed with multiple linear regression models. RESULTS: The nature and number of covariates selected varied with different confounder selection criteria and different cutoffs. Four covariates (i.e., quality of home environment, socioeconomic status (SES), maternal intelligence, and parental smoking behaviour) met the conventional CE criterion (⩾10%), whereas 14 variables met the ST criterion ( p ⩽ 0.25). However, the magnitude of the relationship between blood lead concentration and children's IQ differed slightly after adjustment for confounding, using either the CE (partial regression coefficient: −4.4; 95% confidence interval (CI): −0.5 to −8.3) or ST criterion (−4.3; 95% CI: −0.2 to −8.4). CONCLUSIONS: Identification and selection of confounding factors need to be viewed cautiously in epidemiologic studies. Either the CE (e.g., ⩾ 10%) or ST (e.g., p ⩽ 0.25) criterion may be implemented in identification of a potential confounder if a study sample is sufficiently large, and both the methods are subject to arbitrariness of selecting a cut-off point. In this study, the CE criterion (i.e., ⩾ 10%) appears to be more stringent than the ST method (i.e., p ⩽ 0.25) in the identification of confounders. However, the ST rule cannot be used to determine the trueness of confounding because it cannot reflect the causal relationship between the confounder and outcome. This study shows the complexities one can expect to encounter in the identification of and adjustment for confounders.

Lifetime low-level exposure to environmental lead and children's emotional and behavioral development at ages 11-13 years. The Port Pirie Cohort Study.

The Port Pirie Cohort Study is the first study to monitor prospectively the association between lifetime blood lead exposure and the prevalence of emotional and behavioral problems experienced by children. Lead exposure data along with ratings on the Child Behavior Checklist were obtained for 322 11-13-year-old children from the lead smelting community of Port Pirie, Australia. Mean total behavior problem score (95% confidence interval (CI)) for boys whose lifetime average blood lead concentration was above 15 microg/dl was 28.7 (24.6-32.8) compared with 21.1 (17.5-24.8) in boys with lower exposure levels. The corresponding mean scores (95% CI) for girls were 29.7 (25.3-34.2) and 18.0 (14.7-21.3). After controlling for a number of confounding variables, including the quality of the child's HOME environment (assessed by Home Observation for Measurement of the Environment), maternal psychopathology, and the child's IQ, regression modeling predicted that for a hypothetical increase in lifetime blood lead exposure from 10 to 30 microg/dl, the externalizing behavior problem score would increase by 3.5 in boys (95% CI 1.6-5.4), and by 1.8 (95% CI -0.1 to 11.1) in girls. Internalizing behavior problem scores were predicted to rise by 2.1 (95% CI 0.0-4.2) in girls but by only 0.8 (95% CI -0.9 to 2.4) in boys.

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

To examine the association between environmental exposure to lead and children's intelligence at age 11-13 years, and to assess the implications of exposure in the first seven years of life for later childhood development. Prospective cohort study. 375 children born in or around the lead smelting town of Port Pirie, Australia, between 1979 and 1982. Children's intelligence quotient (IQ) measured at 11-13 years of age. 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 mumol/l (10 to 20 micrograms/dl). Exposure to environmental lead during the first seven years of life is associated with cognitive deficits that seem to persist into later childhood.

Evaluation of the lead Decontamination programme in the leading smelting town of port Pirie (South Australia)

An evaluation of the first five years of the Lead Decontamination Programme in the smelter city of Port Pirie, South Australia, is presented. Following a survey of primary school children in 1982, which showed that a substantial proportion had blood lead levels above 30 μg d1‐1, a Lead Decontamination Programme was established in 1984. Blood lead data were available from routine tests offered at six monthly intervals and from the contemporaneous Port Pirie Cohort Study of neurological impairment. These indicate a reduction in blood levels of approximately 20% after the establishment of the Programme with the proportion of children with levels at or above 25 μg d1‐1approximately halved. In particular, a marked reduction was seen in the levels of children whose homes have been decontaminated. While the evaluation was limited to the use of existing data with no comparison group, it is inferred that these reductions are, at least in part, a result of the Lead Decontamination Programme.

Low Level Lead Exposures and IQ

The Port Pirie cohort study which began in 1979 at the Department of Community Medicine, University of Adelaide, Australia, has been followed into the primary school age range and examines intelligence at the age of 7 years in relation to lifetime exposure to lead.

Environmental exposure to lead and children's intelligence at the age of seven years. The Port Pirie Cohort Study.

Exposure to lead in early childhood is thought to result in delayed neuropsychological development. As yet there is little longitudinal evidence to establish whether these effects persist into later childhood. We measured IQ scores in 494 seven-year-old children from the lead-smelting community of Port Pirie, Australia, in whom developmental deficits associated with elevated blood lead concentrations had already been reported at the ages of two and four years. Exposure to lead was estimated from the lead concentrations in maternal blood samples drawn antenatally and at delivery and from blood samples drawn from the children at birth (umbilical-cord blood), at the ages of 6 and 15 months and 2 years, and annually thereafter. Data relating to known covariates of child development were collected systematically for each child throughout the first seven years of life. We found inverse relations between IQ at the age of seven years and both antenatal and postnatal blood lead concentrations. After adjustment by multiple regression for sex, parents' level of education, maternal age at delivery, parents' smoking status, socioeconomic status, quality of the home environment, maternal IQ, birth weight, birth order, feeding method (breast, bottle, or both), duration of breast-feeding, and whether the child's natural parents were living together, the relation with lead exposure was still evident for postnatal blood samples, particularly within the age range of 15 months to 4 years. For an increase in blood lead concentration from 10 micrograms per deciliter (0.48 mumol per liter) to 30 micrograms per deciliter (1.45 mumol per liter), expressed as the average of the concentrations at 15 months and 2, 3, and 4 years, the estimated reduction in the IQ of the children was in the range of 4.4 points (95 percent confidence interval, 2.2 to 6.6) to 5.3 points (95 percent confidence interval, 2.8 to 7.8). This reduction represents an approximate deficit in IQ of 4 to 5 percent. Low-level exposure to lead during early childhood is inversely associated with neuropsychological development through the first seven years of life.

Port Pirie Cohort study: childhood blood lead and neuropsychological development at age two years.

The Port Pirie Cohort Study is an ongoing prospective study of the relationship between exposure to environmental lead within a lead smelter community, and neuropsychological development in early childhood. Over 600 children, originally recruited during antenatal life, underwent serial blood lead estimations up to two years of age. Systematic interview information was collected on a range of variables, and formal developmental assessment (Bayley Scales of Infant Development) was carried out at 24 months of age. Blood lead concentrations measured antenatally (maternal), at delivery (maternal and umbilical cord) and postnatally at 6, 15 and 24 months were negatively correlated (p less than 0.05) with mental development at 24 months of age. Geometric mean blood lead concentrations (microgram/dl) were 14.3, 20.8 and 21.2 at 6, 15 and 24 months of age respectively. When multiple covariates, including maternal IQ, were controlled for in multiple regression analysis, a statistically significant (p less than 0.01) inverse association was observed between blood lead concentration (PbB) measured at 6 months of age and mental development at 2 years of age. No such association was evident for psychomotor development. When the quality of the home environment (HOME Score) was added to the multiple regression model, the inverse association between blood lead concentration at 6 months of age and mental development at 2 years persisted, albeit less strongly (p = 0.07). From this analysis, it is estimated that a child with with PbB of 30 micrograms/dl at age 6 months will have a deficit of 3.3 points (approximately 3%) on the Bayley Mental Development Scale relative to a child with PbB of 10 micrograms/dl.

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 children's 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 children's mental development (as evaluated with use of the McCarthy Scales of Children's 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 children's 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.

The Port Pirie cohort study: maternal blood lead and pregnancy outcome.

During a three-year period, 831 pregnant women in and around Port Pirie, South Australia--a lead smelter community with longstanding lead pollution--were enrolled in a cohort study to examine prospectively the relation between body lead burden and pregnancy outcome. Three-quarters of the enrolled women were residents of the Port Pirie municipality; the other women lived in adjacent towns and countryside. At 14-20 weeks' gestation, the Port Pirie resident women had a mean blood lead concentration of 10.6 micrograms/dl, while the mean in the other (non-Port Pirie) women was 7.6 micrograms/dl. Similar differences were observed in maternal blood samples taken at 30-36 weeks, at delivery, and from the umbilical cord. These blood lead measures, in conjunction with information collected on other risk factors, were then examined in relation to pregnancy outcome. Among 749 pregnancies followed to completion, pre-term delivery was statistically significantly associated, in a dose-response manner, with maternal blood lead concentration at delivery. Mothers of late fetal deaths (stillbirths) had blood lead concentrations at 14-20 weeks' gestation similar to those of all the other women but had lower concentrations at delivery than the other women. Outcomes of pregnancy for which no association with blood lead was detected were spontaneous abortion, low birthweight (for births at term), intrauterine growth retardation, premature rupture of the membranes, and congenital anomalies.

The Port Pirie Cohort Study: Blood lead concentrations in early childhood

A cohort of over 600 children who were born between 1979 and 1982 and accounted for the great majority of all births in Port Pirie, South Australia, and its immediate environs, underwent capillary blood sampling at the ages of 6 months, 15 months, 2 years, and annually thereafter. The mean blood lead concentration (Pb-B) initially rose markedly, peaked at 2 years of age, and subsequently declined gradually at 3 and 4 years of age. No differences in Pb-B were observed between girls and boys. Secular trends in Pb-B at the age of 2 years that were observed in blood samples taken over the 1981-1984 period suggest that both the drought of 1982 and changes in community behaviour may have accounted for some of the age-related variation. The Pb-B was associated positively with surface soil lead concentrations, with a two-fold variation in mean Pb-B between residential zones within Port Pirie. Pb-B was higher in summer than in winter months at the ages of 6 and 15 months, but not at older ages. These findings suggest that lead in dust influences strongly blood lead concentrations in early childhood.