Low Blood Lead Levels, Parental Education, Physiological Stress, And Neurocognition: A Cohort Study
Lead is a well-known neurotoxicant, however, the neurocognitive and health consequences of low levels of exposure is less known. Furthermore, the disparities in lead-induced outcomes are not well understood, where children experiencing more psychosocial stressors seem to have greater deficits at lower levels of lead exposure compared to others. Additionally, the link between lead exposure and physiological stress responses, a precursor for health and neurocognitive deficits, is under-investigated. This dissertation study examined the relationships among low blood lead levels (BLLs), parental education, and neurocognitive and heart rate variability outcomes. Chapter 2 systematically reviewed the literature on the relationship between low BLLs (≤ 10 mcg/dl) and executive function outcomes across childhood development. Built on findings from the systematic review, Chapter 3 examined the relationships among low BLLs across childhood, parental education, intelligence quotients (IQ), and working memory in early adolescence. As an additional line of inquiry, Chapter 4 examined the relationships between low BLLs across childhood and physiological stress responses in early adolescence, measured via heart rate variability, and the moderating effect of parental education. Chapters 3 and 4 were secondary data analyses of the Jintan China Child Cohort Study. Chapter 2 found that low BLLs were most associated with middle childhood working memory and cognitive flexibility outcomes. Findings from Chapter 3 indicated that low BLLs in early childhood were significantly, negatively associated with early adolescent IQ and not working memory, and further that low parental education had a compounding effect with BLLs to influence IQ. Chapter 4 demonstrated that low BLLs in early childhood were significantly, negatively associated with heart rate variability in early adolescence. Moreover, parental education moderated this relationship. Findings from this dissertation study, summarized in Chapter 5, provide further evidence on the long-term associations between low BLLs in early childhood and neurocognitive outcomes in early adolescence. Further, these results provide new evidence on associations between low BLLs and physiological stress responses. These findings help to contextualize the disparities in lead-induced outcomes, where psychosocial stressors seem to influence the degree of negative outcomes associated with lead exposure.