摘要：Objectives. We estimated the collective burden of mortality from autoimmune diseases among females in the United Kingdom and the effects of death certificate coding changes on this estimate. Methods. We analyzed 1993–2003 England and Wales death certificate data for 3 150 267 females aged 1 year or older. We identified death certificates that listed autoimmune conditions as underlying or contributory causes of death. The percentages of all female deaths attributed to autoimmune disorders and to UK official mortality categories were ranked to determine the leading causes of death. Results. In 2003, autoimmune diseases were the sixth or seventh most frequent underlying cause of death among females in all age groups below 75 years. Results were similar when both underlying and contributory causes of death were considered. The proportion of females dying with an autoimmune disorder remained relatively constant from 1993 to 2003. Analyses indicated that death counts for specific autoimmune diseases had been underestimated. Conclusions. Autoimmune diseases are a leading cause of death among females in England and Wales, but their collective impact remains hidden in current disease classification systems. Grouping these disorders together may help promote research needed to identify common determinants and future prevention strategies. Autoimmune disorders are a group of disabling conditions caused by pathological immune responses directed against host antigens. 1 Autoimmune disorders occur more frequently among women and result in chronic ill health, poor quality of life, and major health care costs. 1 – 3 However, because of the relative lack of population-based studies, remarkably little is known about the collective disease burden associated with autoimmune disorders or their shared environmental triggers. 4 Many national and international organizations assess the burden of disease among a population by ranking the leading causes of death 5 – 8 These rankings provide important information for health policymakers and those responsible for delivering health care, and the rankings highlight areas for further research on prevention or treatment of specific conditions. In ranking lists, deaths from specific causes are grouped into broader mortality categories, typically based on the International Classification of Diseases ( ICD ) system used to code death certificates. 9 , 10 In the ICD classification, conditions are grouped according to pathogenic mechanism (e.g., neoplasms), organ system (e.g., diseases of the circulatory system), or etiology (e.g., external causes of death). Grouping causes of death according to pathogenesis is useful because grouping allows estimation of the collective burden of disease resulting from a specific pathological process and the overall impact of risk factors for the pathological process across all organ systems. However, autoimmune disorders are neglected in the ICD classification, because they are listed for the most part individually under separate organ systems. The combined burden of mortality from autoimmune disorders is therefore hidden. The World Health Organization (WHO) recently developed a list of recommended disease categories to use when grouping causes of death in mortality rankings; this list has been adapted by the UK Office for National Statistics to classify local disease patterns in England and Wales. 11 , 12 The recommended categories continue to be based on pathogenesis, organ systems, and etiology, together with individual conditions of public health importance (e.g., influenza and pneumonia). Regrettably, autoimmune disorders remain neglected in these newer classifications. Walsh and Rau attempted to address this problem by investigating the combined burden of mortality among women attributed to 24 conditions that fulfilled Rose and Bona's criteria for autoimmune disorders. 13 , 14 The Walsh and Rau study, in which 1995 US death certificate data were used, showed that autoimmune diseases as a group were among the top 10 causes of death in US women younger than 65 years. 13 Their findings have been cited widely as evidence that autoimmune disorders are an important but neglected group of diseases that affect women's health. 3 , 15 , 16 However, the Walsh and Rau study involved limitations. First, the version of the ICD used to code deaths in their study ( ICD-9 ) did not include specific codes for some of the autoimmune diseases of interest, allowing only rough estimates of mortality. 9 Second, only underlying cause of death data were assessed; other conditions listed on death certificates as contributory causes of death were excluded. Third, the combined burden of mortality attributable to autoimmune diseases was underestimated because the analyses were restricted to 24 disorders; many additional conditions have been identified in recent years that conform to Rose and Bona's criteria for autoimmune pathogenesis. 1 , 14 To date, no collective burden of UK mortality estimates for autoimmune disorders have been published. The primary objective of our study was to estimate the burden of autoimmune diseases among females in the United Kingdom by analyzing 2003 death certificate data for England and Wales. The ICD-10 was used in coding these data, allowing more specific identification of autoimmune disorders. Information on both underlying and contributory causes of death listed on death certificates was available; in addition, data were available for a larger number of autoimmune disorders than those considered by Walsh and Rau, enabling a fuller analysis of the contribution of autoimmune disorders to female mortality. We also used an earlier (1993–2003) data set that included both ICD-9 - and ICD-10 –coded female deaths to assess the extent to which the number of deaths resulting from certain autoimmune disorders may have been overestimated in ICD-9 –coded data and to examine the effects of other changes in coding rules on autoimmune mortality estimates.
