Blood and Urine Cadmium, Blood Pressure, and Hypertension: A Systematic Review and Meta-analysis

BACKGROUND: Cadmium exposure has been inconsistently related to blood pressure. OBJECTIVES: We updated and reevaluated the evidence regarding the relationships of blood cadmium (BCd) and urine cadmium (UCd) with blood pressure (BP) and hypertension (HTN) in nonoccupationally exposed populations. DATA SOURCES AND EXTRACTION: We searched PubMed and Web of Science for articles on BCd or UCd and BP or HTN in nonoccupationally exposed populations and extracted information from studies that provided sufficient data on population, smoking status, exposure, outcomes, and design. DATA SYNTHESIS: Twelve articles met inclusion criteria: eight provided data adequate for comparison, and five reported enough data for meta-analysis. Individual studies reported significant positive associations between BCd and systolic BP (SBP) among nonsmoking women [beta = 3.14 mmHg per 1 mu g/L untransformed BCd; 95% confidence interval (CI), 0.14-6.14] and among premenopausal women (beta = 4.83 mmHg per 1 nmol/L log-transformed BCd; 95% CI, 0.17-9.49), and between BCd and diastolic BP (DBP) among women (beta = 1.78 mmHg comparing BCd in the 90th and 10th percentiles; 95% CI, 0.64-2.92) and among premenopausal women (beta = 3.84 mmHg per 1 nmol/L log-transformed BCd; 95% CI, 0.86-6.82). Three meta-analyses, each of three studies, showed positive associations between BCd and SBP (p = 0.006) and DBP (p < 0.001) among women, with minimal heterogeneity (I-2 = 3%), and a significant inverse association between UCd and HTN among men and women, with substantial heterogeneity (I-2 = 80%). CONCLUSION: Our results suggest a positive association between BCd and BP among women; the results, however, are inconclusive because of the limited number of representative population-based studies of never-smokers. Associations between UCd and HTN suggest inverse relationships, but inconsistent outcome definitions limit interpretation. We believe a longitudinal study is merited.