Modification of vitamin B6 on the associations of blood lead levels and cardiovascular diseases in the US adults

BACKGROUND: Cardiovascular disease (CVD) is a leading cause of death in the US population. Lead exposure is an important risk factor of CVDs, as is associated with elevated homocysteine level and oxidative stress. We aim to examine whether vitamin B6, which has been shown to reduce homocysteine level, can modify the relationship between blood lead and the risk of CVDs. METHODS: Cross-sectional data on ever-report CVDs (congestive heart failure, coronary heart disease, angina pectoris, heart attack and stroke), blood lead level (BLL) and vitamin B6 in the form of plasma pyridoxal 5'-phosphate were obtained from US National Health and Nutrition Examination Survey 2005–2006 for adults≥20 years old. The association between CVDs and quartiles of BLL was estimated using multivariate logistic regression models adjusted for demographics factors, lifestyle variables, stress variables, comorbidities and CVD biomarkers (C reactive protein, homocysteine, cholesterol) and was stratified by vitamin B6 deficiency level (<20 nmol/L) and median value of vitamin B6 (42.5 nmol/L). RESULTS: Positive associations between BLL and CVDs only appeared in the vitamin B6 deficiency group, with quartile 2 to quartile 4 of BLL showing higher risk of CVDs (OR=3.1, 95% CI 0.9 to 10.6; OR=6.5, 95% CI 1.4 to 30.8; OR=5.5, 95% CI 1.4 to 21.7) compared with quartile 1. When stratified by median value of vitamin B6, a significant association between higher CVD risk with higher BLL was only observed in subjects with low vitamin B6 (p trend=0.004). CONCLUSIONS: Vitamin B6 could modify the association between BLL and CVDs, which suggests a potential value of vitamin B6 in influencing the effects of lead exposure on the cardiovascular system.