Prenatal lead exposure levels averaging 1.34 parts per million in childhood baby teeth were associated with an increased likelihood of depression symptoms in adulthood, according to a recent study.
The researchers analyzed 718 adults from the Saint Louis Baby Tooth—Later Life Health Study who had donated baby teeth between the 1950s and 1970s. Using laser ablation inductively coupled plasma mass spectrometry, they quantified lead concentrations preserved in dentin and enamel layers to allow reconstruction of exposure from the second trimester of gestation through approximately 6 months after birth.
At a mean age of 62 years, participants completed standardized assessments of depressive and anxiety symptoms: the Patient Health Questionnaire-9 and the Generalized Anxiety Disorder Screener-7. Outcomes were dichotomized using clinical thresholds (scores of at least 10). Logistic regression models were adjusted for age, sex, parental education, maternal smoking during pregnancy, and early-life socioeconomic factors.
Each interquartile range increase in combined early-life lead exposure corresponded with 1.9 times the odds of major depressive disorder in later adulthood. The third trimester emerged as the most sensitive exposure window, during which lead exposure corresponded with 1.55 times the odds of major depressive disorder. When both the second and third trimesters were modeled together, only the third trimester remained significant at 2 times the odds of depression. "To put our findings into perspective, a shift from the 10th to 90th percentile (1.87 ppm) of third trimester lead exposure in this population is associated with a nearly 3 times the odds of experiencing major depressive disorder in later adulthood, an estimate comparable with that observed for well-established risk factors, such as being overweight and developing type 2 diabetes.," noted lead author Joyce J. Y. Lin, PhD, of the Department of Environmental Health at Harvard T.H. Chan School of Public Health in Boston, Massachusetts, with colleagues. Sex-stratified analyses showed stronger associations among female participants, for whom odds of depression were 1.79 times compared with males, who had 0.97 times the odds of depression, though the difference was not statistically significant.
No statistically significant associations were observed between early-life lead exposure and generalized anxiety disorder in later adulthood. However, continuous anxiety symptom models indicated that late prenatal and early postnatal lead exposure were associated with greater anxiety symptom scores; specifically 0.36 and 0.48 times the odds, respectively.
In the US, as adults who experienced higher levels of lead exposure in childhood grow older, expanded screening and mental health service access may be warranted, the authors concluded. Worldwide, they added, in regions where lead exposure among children remains elevated, the findings highlight the long-term health effects of early exposure and the need to consider later-life outcomes when evaluating the benefits of reducing lead exposure in childhood.
Scott M. Bartell, PhD, received consulting fees from Harvard University for work on this project, which was supported by a National Institutes of Health grant to Harvard. Marc G. Weisskopf, PhD, reported receiving grants from the National Institutes of Health during the study. No additional disclosures were reported.
Source: JAMA Psychiatry