Association of Childhood Blood Lead Levels With Cognitive Function and Socioeconomic Status at Age 38 Years and With IQ Change and Socioeconomic Mobility Between Childhood and Adulthood

Abstract

Importance Many children in the US and around the world are exposed to lead, a developmental neurotoxin. The long-term cognitive and socioeconomic consequences of lead exposure are uncertain. Objective To test the hypothesis that childhood lead exposure is associated with cognitive function and socioeconomic status in adulthood and with changes in IQ and socioeconomic mobility between childhood and midlife. Design, Setting, and Participants Prospective cohort study based on a population-representative 1972–73 birth cohort from New Zealand, the Dunedin Multidisciplinary Health and Development Study, followed to age 38 years (December, 2012). Exposure Childhood lead exposure ascertained as blood-lead levels measured at 11 years. High blood-lead levels were observed among children from all socioeconomic status levels in this cohort. Main Outcomes and Measures The IQ (primary outcome) and indexes of Verbal Comprehension, Perceptual Reasoning, Working Memory, and Processing Speed (secondary outcomes) were assessed at 38 years using the Wechsler Adult Intelligence Scale–IV (WAIS-IV; IQ range 40–160). Socioeconomic status (primary outcome) was assessed at 38 years using the New Zealand Socioeconomic Index-2006, (NZSEI-06; range 10=lowest-90=highest). Results Of 1037 original participants, 1007 were alive at 38 years, of whom 565 (56%) had been lead tested at 11 years (54% male; 93% white). Mean blood-lead level at 11 years was 10.99μg/dL (SD=4.63). Among blood-tested participants included at 38 years, mean WAIS-IV score was 101.16 (SD=14.82) and mean NZSEI-06 score was 49.75 (SD=17.12). After adjusting for maternal IQ, childhood IQ, and childhood socioeconomic status, each 5μg/dL higher level of blood-lead in childhood was associated with a 1.61-point lower score (95%CI:−2.48, −0.74) in adult IQ, a 2.07-point lower score (95%CI: −3.14, −1.01) in Perceptual Reasoning, and a 1.26-point lower score (95%CI: −2.38, −0.14) in Working Memory. Lead-associated deficits in Verbal Comprehension and Processing Speed were not statistically significant. After adjusting for confounders, each 5μg/dL higher level of blood-lead in childhood was associated with a 1.79-unit lower score (95%CI: −3.17, −0.40) in socioeconomic status. An association between greater blood-lead levels and a decline in IQ and socioeconomic status from childhood to adulthood was observed, with 40% of the association with downward mobility mediated by cognitive decline from childhood. Conclusion and Relevance In this cohort born in New Zealand in 1972–1973, childhood lead exposure was associated with lower cognitive function and socioeconomic status at age 38 years and with declines in IQ and downward social mobility. Childhood lead exposure may have long-term ramifications.

Lead toxicity in a new-born due to in utero exposure

“…3 A recent cohort study in New Zealand of children exposed to lead level of 10.9 mcg/dL, showed a decline in IQ and socioeconomic status during adulthood after being corrected for maternal IQ, childhood IQ, and childhood socioeconomic status, suggesting that lead toxicity persists into adulthood. 4 We did not observe any neurologic sequelae during the hospital course of our patient. However, the long-term outcome remains to be seen.…”

Poisoned Development: Assessing Childhood Lead Exposure as a Cause of Crime in a Birth Cohort Followed Through Adolescence

“…Once in the body, lead mimics calcium, impairing brain development and neurotransmitter systems in ways that disrupt executive functioning and mood regulation, which in turn reduces impulse control and the inhibition of aggressive behaviors (Cecil et al, 2008;Feigenbaum and Muller, 2016;Lidsky and Schneider, 2003;Needleman, 2004;Winter and Sampson, 2017). Through the same age-graded mechanisms, lead exposure is associated with reduced cognitive ability (Lanphear et al, 2005;Reuben et al, 2017) and increased attention-deficit/hyperactivity disorder (Goodlad, Marcus, and Fulton, 2013), both of which are predictors of delinquent behavior in the criminological literature (Farrington, 1998;Moffitt, 1993). The damage of lead poisoning is not considered reversible, which is why pediatricians so strongly emphasize prevention (Centers for Disease Control and Prevention [CDC], 1991).…”

Lead (Pb) Bioaccessibility and Mobility Assessment of Urban Soils and Composts: Fingerprinting Sources and Refining Risks to Support Urban Agriculture

“…There is no safe level of Pb exposure, and even a small dose can cause serious intellectual deficits and increase the likelihood of depression, anxiety, and other detriments (Bellinger et al, 1991;Lanphear et al, 2005;Bouchard et al, 2009;World Health Organization, 2014). Pb poisoning is particularly harmful for children, and the impacts of childhood exposure are felt throughout an individual's life since Pb can accumulate in bone and permanent cognitive deficits can lower socioeconomic mobility in adulthood (Reuben et al, 2017).…”