Pitfalls in the study using death certificates to demonstrate the reversibility of mortality from diabetes in the blackfoot disease endemic areas in Taiwan [1]
Journal
Journal of Occupational and Environmental Medicine
Journal Volume
48
Journal Issue
8
Pages
755
Date Issued
2006
Author(s)
Abstract
To the Editor: I read the recently published paper by Chiu et al1 demonstrating the reversibility of mortality from diabetes in the blackfoot disease (BFD) endemic areas of Taiwan from 1971 to 2000 with great interest. This study calculated the standardized mortality ratios by using death certificates and has found a decreasing mortality from diabetes in females but not in males in four BFD townships (ie, Peimen, Hsuechia, Putai, and Ichu). The authors concluded that “based on the reversibility criterion, the association between arsenic exposure and DM is likely to be causal for females but not in males.” I would like to point out several pitfalls in the interpretations of the results of this study. First, the study period falls behind a time when artesian well water had been replaced by tap water in these townships. Therefore, we do not know for sure whether the mortality from diabetes was really high at the time when BFD was most rampant during the 1950s and 1960s.2 The authors should have extended the study period one or two decades before the implementation of tap water to contrast the mortality before and after the implementation of tap water. Second, the conclusion from such an analysis of the death certificates that arsenic exposure could be causal for diabetes in females but not in males is too dogmatic because this is neither a follow-up study nor is the use of death certificates a solid enough indicator for diabetes occurrence. It has been demonstrated by a recent study that only 28.8% of the patients with diabetes who died would have diabetes listed as the underlying cause of death in their death certificates in Taiwan.3 Furthermore, the authors should have assumed that the behavior of the physicians to list diabetes as an underlying cause of death would be similar in the BFD endemic areas and in other regions of Taiwan and that this behavior would not have changed over the period of time within the study. This is apparently not the case. The authors also neglected the possible influence of competitive causes of death. In addition, the authors might not be correct that International Classification of Diseases, 9th Revision has been used as early as the 1970s. Third, as described by the authors, the population in the BFD endemic areas decreased from 139,051 in 1971 to 100,771 in 2000. This is in contrary to the growing of the total population in Taiwan over the period. The migration out of the endemic region, especially for the highly exposed subjects, could greatly influence the patterns and causes of mortality over time. Fourth, the authors asserted that a differential accessibility in medical care might not be responsible for the observed results. This might be true in recent years but was not the case during the early years of the study. Fifth, in the interpretation of the differential trends in the changes of standardized mortality ratios between men and women, the suggestion by the authors that “women might have drunk more local water than men and thus the impact of the cessation of consumption of the high arsenic well water was more important in women” is speculative without scientific evidence. The authors also suggested that women might be more susceptible to arsenic exposure than men based on the observation that women had a higher prevalence of diabetes than men had in the BFD areas. This might not be correct because the incidence study on diabetes in the BFD areas did not show a significant difference between men and women.4 Again, the suggestion that men might have higher body mass index or triglycerides than women might have in the BFD areas is not supported by evidence. Chin-Hsiao Tseng, MD, PhD Division of Endocrinology and Metabolism Department of Internal Medicine National Taiwan University Hospital Taipei Medical University Taipei, Taiwan
SDGs
Other Subjects
arsenic; tap water; well water; arsenic poisoning; blackfoot disease; body mass; death certificate; diabetes mellitus; gender; human; international classification of diseases; letter; mortality; Taiwan; Arsenic Poisoning; Data Interpretation, Statistical; Death Certificates; Diabetes Mellitus; Female; Humans; Male; Mortality; Peripheral Vascular Diseases; Sex Factors; Taiwan; Time Factors; Water Pollutants, Chemical; Water Supply
Type
letter