Nonlinear association between blood lead and hyperhomocysteinemia among adults in the United States

Evidence regarding the association between blood lead levels (BLL) and hyperhomocysteinemia (HHcy) in US adults was limited. We aimed to investigate the association of BLL with the risk of HHcy, and to examine possible effect modifiers using US National Health and Nutrition Examination Survey (NHANES) database. We performed a cross-sectional study using data from up to 9,331 participants aged ≥ 20 years of NHANES from 2001 to 2006. BLL was measured by atomic absorption spectrometry. HHcy was defined as plasma homocysteine level > 15 µmol/L. The weighted prevalence of HHcy was 6.87%. The overall mean BLL was 1.9 μg/dL. Overall, there was a nonlinear positive association between Ln-transformed BLL (LnBLL) and the risk of HHcy. The Odds ratios (95% CI) for participants in the second (0.04–0.49 μg/dL), third (0.5–0.95 μg/dL) and fourth quartiles (> 0.95 μg/dL) were 1.12 (95% CI: 0.71, 1.76), 1.13 (95% CI: 0.73, 1.77), and 1.67 (95% CI: 1.07, 2.61), respectively, compared with those in quartile 1. Consistently, a significantly higher risk of HHcy (OR: 1.49; 95% CI: 1.19, 1.88) was found in participants in quartile 4 compared with those in quartiles 1–3. Furthermore, a strongly positive association between LnBLL and HHcy was observed in participants with estimated glomerular filtration rate (eGFR) −1/1.73 m−2. Our results suggested that a higher level of BLL (LnBLL > 0.95 μg/dL) was associated with increased risk of HHcy compared with a lower level of BLL (LnBLL ≤ 0.95 μg/dL) among U.S. adults, and the association was modified by the eGFR.