| Mortality from Ischemic Heart Disease and Diabetes Mellitus (Type 2) in Four U.S. Wheat-Producing States: A Hypothesis-Generating Study Dina M. Schreinemachers National Health and Environmental Effects Research Laboratory, Office of Research and Development, U.S. Environmental Protection Agency, Research Triangle Park, North Carolina, USA Abstract
In this ecologic study I examined ischemic heart disease (IHD) and diabetes mortality in rural agricultural counties of Minnesota, Montana, North Dakota, and South Dakota, in association with environmental exposure to chlorophenoxy herbicides, using wheat acreage as a surrogate exposure. I collected data on agricultural land use and 1979-1998 mortality from the U.S. Department of Agriculture and the Centers for Disease Control and Prevention websites, respectively. Counties were grouped based on percentage of land area dedicated to wheat farming. Poisson relative risks (RR) and 95% confidence intervals (CIs) , comparing high- and medium- with low-wheat counties, were obtained for IHD, the subcategories acute myocardial infarction (AMI) and coronary atherosclerosis (CAS) , and diabetes, adjusting for sex, age, mortality cohort, and poverty index. Mortality from IHD was modestly increased (RR = 1.08 ; 95% CI, 1.04-1.12) . Analyses of its two major forms were more revealing. Compared with low-wheat counties, mortality in high-wheat counties from AMI increased (RR = 1.20 ; 95% CI, 1.14-1.26) , and mortality from CAS decreased (RR = 0.89 ; 95% CI, 0.83-0.96) . Mortality from AMI was more pronounced for those < 65 years of age (RR = 1.31 ; 95% CI 1.22-1.39) . Mortality from type 2 diabetes increased (RR = 1.16 ; 95% CI, 1.08-1.24) . These results suggest that the underlying cause of mortality from AMI and type 2 diabetes increased and the underlying cause of mortality from CAS decreased in counties where a large proportion of the land area is dedicated to spring and durum wheat farming. Firm conclusions on causal inference cannot be reached until more definitive studies have been conducted. Key words: chlorophenoxy herbicides, clofibrate, coronary atherosclerosis, C-reactive protein, diabetes, ischemic heart disease, myocardial infarction. Environ Health Perspect 114: 186-193 (2006) . doi:10.1289/ehp.8352 available via http://dx.doi.org/ [Online 6 October 2005]
Address correspondence to D.M. Schreinemachers, Epidemiology and Biomarkers Branch, Human Studies Division, National Health and Environmental Effects Research Laboratory, U.S. Environmental Protection Agency, MD 58A, Research Triangle Park, NC 27711 USA. Telephone: (919) 966-5875. Fax: (919) 966-7584. E-mail: schreinemachers. dina@epa.gov I am grateful to the late O. Axelson for his support and for sharing his insight into the clofibrate-chlorophenoxy herbicide connection. I thank L. Birnbaum, J. Creason, B. Hilborn, P. Mendola, and especially V. Garry for their review of the manuscript. I also thank the anonymous EHP reviewers for their useful comments. The research described in this article has been reviewed in accordance with U.S. Environmental Protection Agency policy and approved for publication. Approval does not signify that the contents necessarily reflect the views and policies of the agency. The author declares she has no competing financial interests. Received 24 May 2005 ; accepted 6 October 2005. The full version of this article is available for free in HTML or PDF formats. |
