Prenatal Pesticide Exposure and Early Alzheimer Disease-Related Biomarker and Cognitive Changes in Midlife

Importance: Alzheimer disease (AD) pathogenesis begins decades before clinical symptoms, yet environmental determinants of early disease risk, particularly during fetal development, remain largely uncharacterized. Prenatal exposure to dichlorodiphenyldichloroethylene (DDE), the primary persistent metabolite of DDT, is a biologically plausible early-life contributor to AD risk given long half-life in human tissue and higher levels observed in AD patients. However, prospective human evidence linking prenatal DDE to midlife AD-relevant outcomes is absent. Objective: To determine whether prenatal DDE exposure is associated with plasma AD biomarkers and cognitive performance in early midlife offspring, and whether APOE {epsilon}4 genotype modifies these associations. Design: Observational cohort analysis nested within the Child Health and Development Studies (CHDS), a population-based birth cohort. Setting: CHDS enrolled pregnant women between 1959-1967 in the San Francisco Bay Area. Participants: Among 367 eligible adult offspring who participated in a follow-up study (2010-2013) at mean age 49.3 years, 179 with available prenatal DDE measurements were included. Main Outcomes and Measures: Prenatal DDE levels from maternal serum. Primary outcomes were plasma A{beta}42/40 ratio and Digit Symbol Substitution Test (DSST) performance. Secondary outcomes included plasma pTau217, GFAP, NfL and APOE genotype. Results: Among 179 participants (56% female; 26% APOE {epsilon}4 carriers), mean prenatal DDE was 47.4 (25.4) ng/mL. Higher prenatal DDE was associated with lower DSST scores ({beta}=-0.021, 95% CI, -0.041 to -0.001, P=0.039) and lower plasma A{beta}42/40 ratio ({beta}=-0.079, 95% CI, -0.133 to -0.024, P=0.005) per ng/mL DDE, adjusting for sex, race, education, and APOE {epsilon}4 status. Associations were strongest among APOE {epsilon}4 non-carriers for DSST ({beta}=-0.033, 95% CI, -0.050 to -0.016, P=0.001) and A{beta}42/40 ratio ({beta}=-0.101, 95% CI, -0.161 to -0.040, P=0.001). No significant associations were observed for pTau217, GFAP, or NfL. Conclusions and Relevance: In this prospective birth cohort study, prenatal exposure to a persistent environmental toxicant was associated with lower plasma A{beta}42/40 ratio and worse cognitive performance in early midlife, consistent with DDE accelerating the preclinical trajectory of AD-related biological changes decades before symptom onset. These findings support a life-course framework for AD risk and identify prenatal DDE as a potentially modifiable determinant of early AD-related pathology amenable to prevention.