The Association between Blood Lead Levels and Osteoporosis among Adults—Results from the Third National Health and Nutrition Examination Survey (NHANES III)

BACKGROUND: Osteoporosis is a reduction in bone mass sufficient to increase the risk of fracture. Lead exposure during childhood may be a risk factor for low bone mineral density (BMD). Basic-science research demonstrates that lead exposure is associated with a decrease in BMD in animals. However, human studies are limited. OBJECTIVE: Our objective was to conduct a secondary analysis of a national database to explore the association between lead exposure and osteoporosis in adult humans. METHODS: In this study we used data from the Third National Health and Nutrition Examination Survey (NHANES III). We analyzed subjects who were ≥ 50 years of age. A concurrent venous blood lead level defined lead exposure. The primary outcome variable was the BMD of the total hip. We conducted analyses on four groups: non-Hispanic white men, non-Hispanic white women, African-American men, and African-American women. We conducted bivariate analyses between covariates known to be associated with bone density (i.e., age, body mass index, calcium intake, ethanol/tobacco consumption, physical activity, socioeconomic status) and the total hip BMD. The significant covariates were introduced into analysis of covariance to determine the association between BMD and blood lead level tercile. RESULTS: The adjusted mean total hip BMD among non-Hispanic white males with a blood lead level in the lowest tercile versus the highest tercile was 0.961 g/cm(2) and 0.934 g/cm(2), respectively (p < 0.05). We also found a similar association among white females, but the difference was marginally significant (0.05 < p < 0.10). CONCLUSIONS: We found a significant inverse association between lead exposure and BMD, but only among white subjects. However, because of the cross-sectional design of NHANES, we cannot make inferences about the temporal sequence of this association. With the large number of adults who had lead exposure in the past and the morbidity associated with osteoporosis, further inquiry is necessary on the possible casusal association between lead exposure and osteoporosis in humans.