Women’s Health
Oral contraceptive pill use and blood lead concentrations in U.S. premenopausal individuals: Results from NHANES 2003-2012 Kristen Upson* Arianna Foster Mandy S. Hall Nicole M. Talge Dorothy R. Pathak Renee Heffron Robert O. Wright Julio Landero Michael Yin Flavia Matovu Quaker E. Harmon Kenneth Mugwanya Andrew Mujugira Chenxi Li Kristen Upson
Oral contraceptives (OCs) are used by 151 million people worldwide for pregnancy prevention and management of menstrual disorders. Most OCs contain estrogen, which can have a bone-sparing effect by suppressing osteoclast activity. We hypothesized that lower bone turnover with current OC use decreases mobilization of toxic metal lead (Pb) stored in bone to blood. To investigate whether current OC use is associated with lower blood Pb concentrations, we conducted a cross-sectional analysis using data from the National Health and Nutrition Examination Survey (NHANES) for years 2003-2012. The study population comprised premenopausal, non-pregnant individuals ages 20-44 years with an intact uterus, at least one ovary, and not currently using injectable contraception, who had data available on current OC use and blood Pb concentrations (unweighted n=2,884). We used multivariable linear regression to estimate the percent difference in blood Pb concentrations and 95% CI between current OC users and non-users (defined as those not currently using OCs); we adjusted for potential confounding factors and accounted for the complex survey sampling design. The geometric mean blood Pb concentrations in current OC users and non-users were 0.71 µg/dl (95%CI: 0.67, 0.75) and 0.84 µg/dl (95%CI: 0.82, 0.87), respectively. After adjustment, current OC users had 11% lower blood Pb levels (95%CI: -16%, -5%) than non-users. The association persisted in analyses (i) limited to never-smokers (unweighted n=1,784) to address potential residual confounding from smoking, a substantial source of blood Pb (-10%, 95%CI: -17%, -3%), and (ii) additionally adjusting for anemia status; Pb resides in red blood cells and OCs users tend to have less menstrual blood loss (-10%, 95%CI: -16%, -5%). As no safe level of blood Pb exists, and Pb can adversely affect all organ systems, even in adulthood, further research is warranted to replicate our findings of lower blood Pb concentrations with current OC use.