Scientists Dispute JAMA Study Linking BPA Exposure to Type 2 Diabetes
Three letters published in the Febuary 18, 2009, edition of the Journal of the American Medical Association (JAMA) have raised questions about a study linking bisphenol A (BPA) exposure to cardiovascular disease, type 2 diabetes and liver enzyme abnormalities in adults. Led by British researcher Iain D. Lang, the study concluded that participants in the Centers for Disease Control and Prevention’s National Health and Nutrition Examination Survey 2003-2004 (NHANES) who had the highest BPA exposure were three times as likely to develop cardiovascular disease and twice as likely to develop type 2 diabetes. In addition, a concurrent JAMA editorial hailed these results as the “first major epidemiologic study to examine the health effects associated with the ubiquitous estrogenic chemical bisphenol A.” The editorial board consequently urged “U.S. regulatory agencies to follow the recent action taken by Canadian authorities, which have declared BPA a ‘toxic chemical’ requiring aggressive action to limit human and environmental exposures.”
The responses to the study have apparently pointed to potential flaws in both methodology and statistical analysis. In particular, scientists from the National Institute for Statistical Sciences and the University of British Columbia noted that the NHANES “measured 275 environmental chemicals and a wide range of health outcomes.” Their joint letters argued that there are approximately 9 million statistical
models available to analyze the NHANES data, and urged future researchers to “develop a statistical analysis strategy that takes into account the large number of questions at issue.” “Given the number of questions at issue and possible modeling variations in the CDC design, the findings reported by the authors could well be the result of chance,” concludes the letter, which prompted Lang and his colleagues to
describe such criticism as nothing new and to again emphasize the need for replication studies. Additional information about the original study appears in issue 275 of this Update. See FoodProductionDaily.com, February 19, 2009.
