Peripheral arterial disease and metals: Navas-Acien et al. respond.We thank Plusquin et al. for their interest in our analysis of the 1999-2000 National Health and Nutrition Examination Survey (NHANES NHANES National Health and Nutrition Examination Survey (US CDC) ) data on the association of lead, cadmium, and other metals with the prevalence of peripheral arterial disease (PAD) (Navas-Acien et al. 2004; Navas-Acien et al. 2005). After analyzing data from 428 participants in the Flemish Study on Environment, Genes, and Health Outcomes, Plusquin et al. confirmed our findings of a positive and strong association between blood lead or cadmium with PAD. They also reported a nonstatistically significant trend for the association of 24-hr urinary cadmium with the prevalence of PAD; however, in the absence of information on relevant methodologic details, such as the number of subjects with PAD, this nonsignificant non·sig·nif·i·cant adj. 1. Not significant. 2. Having, producing, or being a value obtained from a statistical test that lies within the limits for being of random occurrence. result is difficult to interpret. Overall, the findings of Plusquin et al. add to the growing concern about the cardiovascular effects of environmental exposure to low concentrations of metals (Weinhold 2004). On a more general note, both the NHANES study, which was the basis of our analyses, and the Flemish Study on Environment, Genes, and Health Outcomes (Plusquin et al.) used cross-sectional designs. These designs have important limitations for assessing the causal effects of exposures on cardiovascular risk, even when the outcome is a subclinical subclinical /sub·clin·i·cal/ (sub-klin´i-k'l) without clinical manifestations. sub·clin·i·cal adj. Not manifesting characteristic clinical symptoms. Used of a disease or condition. marker such as PAD defined using the ankle-braquial blood pressure index. Some limitations of cross-sectional designs include survivor effects for severe cases of cardiovascular disease Cardiovascular disease Disease that affects the heart and blood vessels. Mentioned in: Lipoproteins Test cardiovascular disease , potential changes in biomarker levels associated with disease development or with cardiovascular medications, and changes in exposure patterns associated with the development of disease. Although cross-sectional studies are important first steps in evaluating the cardiovascular effects of environmental exposures, prospective studies ultimately will provide more rigorous tests of causality causality, in philosophy, the relationship between cause and effect. A distinction is often made between a cause that produces something new (e.g., a moth from a caterpillar) and one that produces a change in an existing substance (e.g. . For cadmium, there are no prospective studies using biomarkers of exposure and adequate measures of cardiovascular disease incidence and mortality, whereas for lead the prospective evidence is limited (Lustberg and Silbergeld 2002; Moiler and Kristensen 1992; Pocock et al. 1988). Because of the frequent environmental exposure to lead, cadmium, and other metals; the existence of a biological basis for cardiovascular effects of metals; and the current controversies on safety standards Safety standards are standards designed to ensure the safety of products, activities or processes, etc. They may be advisory or compulsory and are normally laid down by an advisory or regulatory body that may be either voluntary or statutory. , performing high quality prospective studies with appropriate biomarkers of exposure and standardized cardiovascular outcome definitions is a public health research priority. The authors declare they have no competing financial interests. Ana Navas-Acien Ellen K. Silbergeld Eliseo Guallar Johns Hopkins University Johns Hopkins University, mainly at Baltimore, Md. Johns Hopkins in 1867 had a group of his associates incorporated as the trustees of a university and a hospital, endowing each with $3.5 million. Daniel C. Bloomberg School of Public Health Baltimore, Maryland "Baltimore" redirects here. For the surrounding county, see Baltimore County, Maryland. For other uses, see Baltimore (disambiguation). Baltimore is an independent city located in the state of Maryland in the United States. E-mail: eguallar@jhsph.edu REFERENCES Lustberg M, Silbergeld E. 2002. Blood lead levels and mortality. Arch Intern intern /in·tern/ (in´tern) a medical graduate serving in a hospital preparatory to being licensed to practice medicine. in·tern or in·terne n. Med 162:2443-2449. Moiler L, Kristensen TS. 1992. Blood lead as a cardiovascular risk factor. Am J Epidemiol 136:1091-1100. Navas-Acien A, Selvin E, Sharrett AR, Calderon-Aranda E, Silbergeld E, Guallar E. 2004. Lead, cadmium, smoking, and increased risk of peripheral arterial disease. Circulation 109:3196-3201. Navas-Acien A, Silbergeld EK, Sharrett R, Calderon-Aranda E, Selvin E, Guallar E. 2005. Metals in urine and peripheral arterial disease. Environ Health Perspect 113:164-169. Weinhold B. 2004. Environmental cardiology cardiology Medical specialty dealing with heart diseases and disorders. It began with the 1749 publication by Jean Baptiste de Sénac of contemporary knowledge of the heart. Diagnostic methods improved in the 19th century, and in 1905 the electrocardiograph was invented. : getting to the heart of the matter. Environ Health Perspect 112:A880-A887. |
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