Underlying cause-of-death mortality statistics: considering the reliability of data]

Mortality statistics are used in epidemiology and public health as an indicator of health status, to evaluate health programs, and in population studies to compare trends and spatial differences. One of the variables used in this type of analysis is the underlying cause-of-death. However, the quality of cause-of-death statistics based on the information recorded by physicians in death certificates has been criticized. The aim of this paper is to discuss the reliability of cause-of-death data recorded by physicians in death certificates, based on studies carried out according to various methodologies, and to comment on the validity of using such underlying cause-of-death statistics.     

Validation of cause-of-death statistics in urban China

BACKGROUND: National vital registration systems are the principal source of cause specific mortality statistics, and require periodic validation to guide use of their outputs for health policy and programme purposes, and epidemiological research. We report results from a validation of cause of death statistics from health facilities in urban China. METHODS: 2917 deaths from health facilities located in six cities in China constituted the study sample. A reference diagnosis of the underlying cause was derived for each death, based on expert review of available medical records, and compared with that filed at registration. Sensitivity, specificity and positive predictive value were computed for specific causes/cause categories according to the International Classification of Diseases (ICD), including analyses based on quality of evidence scores for each cause. Patterns of misclassification by the registration system were studied for individual causes of death. RESULTS: The registration system had good sensitivity in diagnosing cerebrovascular disease and several site specific cancers (lung, liver, stomach, colorectal, breast and pancreas). Sensitivity was average (50-75%) for some major causes of adult death in China, namely ischaemic heart disease (IHD), chronic obstructive lung disease (COPD), diabetes, and liver and kidney diseases, with compensatory misclassification patterns observed between several of them. Sensitivity was particularly low for hypertensive disease. CONCLUSIONS: Although diagnostic misclassification is not uncommon in urban death registration data, they appear to balance each other at the population level. Compensating misclassification errors suggest that caution is required when drawing conclusions about particular chronic causes of adult death in China. Investment is required to improve the quality of cause attribution for health facility deaths, and to assess the validity of cause attribution for home deaths. Periodic assessments of the quality of cause of death statistics will enhance their usability for health policy and epidemiological research.     

The reliability of cause-of-death coding in The Netherlands

Cause-of-death statistics are a major source of information for epidemiological research or policy decisions. Information on the reliability of these statistics is important for interpreting trends in time or differences between populations. Variations in coding the underlying cause of death could hinder the attribution of observed differences to determinants of health. Therefore we studied the reliability of cause-of-death statistics in the Netherlands. We performed a double coding study. Death certificates from the month of May 2005 were coded again in 2007. Each death certificate was coded manually by four coders. Reliability was measured by calculating agreement between coders (intercoder agreement) and by calculating the consistency of each individual coder in time (intracoder agreement). Our analysis covered an amount of 10,833 death certificates. The intercoder agreement of four coders on the underlying cause of death was 78%. In 2.2% of the cases coders agreed on a change of the code assigned in 2005. The (mean) intracoder agreement of four coders was 89%. Agreement was associated with the specificity of the ICD-10 code (chapter, three digits, four digits), the age of the deceased, the number of coders and the number of diseases reported on the death certificate. The reliability of cause-of-death statistics turned out to be high (>90%) for major causes of death such as cancers and acute myocardial infarction. For chronic diseases, such as diabetes and renal insufficiency, reliability was low (<70%). The reliability of cause-of-death statistics varies by ICD-10 code/chapter. A statistical office should provide coders with (additional) rules for coding diseases with a low reliability and evaluate these rules regularly. Users of cause-of-death statistics should exercise caution when interpreting causes of death with a low reliability. Studies of reliability should take into account the number of coders involved and the number of codes on a death certificate.     

Melanoma of the skin in the national cause-of-death statistics and in the hospital statistics

In the last 40 years the national mortality from melanoma of the skin, corrected for age, has increased by over 300%. Figures for males are always higher than those for females and this difference tends to grow larger. Since 1960 it has mostly been the mortality in the age groups 30-69 years that increased. The rise in mortality of older persons has been relatively small. Among the patients treated clinically, females are in the majority and increasingly so from year to year. Probability of survival is better for females than for males. Major shifts seem to occur in the localization of the lesion. Lesions are localized relatively less often in the skin of the head. In males, it is the frequency of melanomas of the trunk that is rising, while melanomas of the extremities are markedly increasing in frequency in both males and females.     

Evaluating national cause-of-death statistics: principles and application to the case of China

Mortality statistics systems provide basic information on the levels and causes of mortality in populations. Only a third of the world's countries have complete civil registration systems that yield adequate cause-specific mortality data for health policy-making and monitoring. This paper describes the development of a set of criteria for evaluating the quality of national mortality statistics and applies them to China as an example. The criteria cover a range of structural, statistical and technical aspects of national mortality data. Little is known about cause-of-death data in China, which is home to roughly one-fifth of the world's population. These criteria were used to evaluate the utility of data from two mortality statistics systems in use in China, namely the Ministry of Health-Vital Registration (MOH-VR) system and the Disease Surveillance Point (DSP) system. We concluded that mortality registration was incomplete in both. No statistics were available for geographical subdivisions of the country to inform resource allocation or for the monitoring of health programmes. Compilation and publication of statistics is irregular in the case of the DSP, and they are not made publicly available at all by the MOH-VR. More research is required to measure the content validity of cause-of-death attribution in the two systems, especially due to the use of verbal autopsy methods in rural areas. This framework of criteria-based evaluation is recommended for the evaluation of national mortality data in developing countries to determine their utility and to guide efforts to improve their value for guiding policy.     

Multiple cause-of-death analysis of hypertension-related mortality in New York State

Multiple cause-of-death data--that is, records of all medical conditions listed on death certificates--are used to study hypertension mortality in New York State during 1968-82. Mortality rates based on underlying causes for ischemic heart disease (IHD) and stroke are selected for comparison. During 1968-78, white women showed the largest age-adjusted decline of all race-sex groups for hypertension, as white men did for stroke and nonwhite men did for IHD. White men showed the largest age-adjusted decline for all three diseases for 1979-82. In general, declines in hypertension death rates are more comparable to declines in stroke mortality than to IHD mortality.     

The use of cause-of-death statistics for health situation assessment: national and international experiences

About 80 countries or areas regularly report detailed cause-of-death data to WHO based on the International Statistical Classification of Diseases, Injuries, and Causes of Death (ICD). These data refer to about 35% of all deaths estimated to occur in the world, although the actual coverage may be somewhat higher due to the representativeness of data-collection schemes in countries such as China. These data are systematically validated and documented by WHO before their dissemination, principally through publication in the World health statistics annual. This article describes the collection and use of these data by WHO for assessing the global and regional health situation, and for monitoring trends in health status. In addition, several issues in the use of mortality data and the ICD for national health situation assessment are discussed, including the need for documenting the quality and coverage of cause-of-death statistics, identifying biases and evaluating mortality trends.     

Mutual relationship between prevalence statistics and mortality statistics in Parkinson's disease

OBJECTIVE: The purpose of this study is to determine whether the statistics from three published reports on Parkinson's disease (PD) are mutually interrelated and to clarify the relationship between the prevalence statistics and mortality statistics of PD. These statistics included data on "number of patients with PD (PD Patients)", "number of patients with PD receiving financial aid for treatment (PD Recipients)" as an indicator showing the prevalence of PD, and "number of deaths from PD (PD Deaths, i.e., mortality)". METHODS: The data on PD Patients, PD Recipients and PD Deaths were cited from "Patient Survey" by Ministry of Health, Labour and Welfare, a report by the Research Committee on Epidemiology of Intractable Diseases and "Vital Statistics of Japan" by Ministry of Health, Labour and Welfare, respectively. The expected PD Patients, PD Recipients and PD Deaths were calculated as products of their respective rates for the entire country and prefecture population, adjusting for a difference in population composition. Observed/expected number ratios (O/E ratio) of PD Patients, PD Recipients and PD Patients were calculated by prefecture. The correlation between the O/E ratios was examined. In addition, the relationships of the O/E ratios with the number of hospitals or physicians per person were examined. RESULTS: There were no significant correlations between the O/E ratios of PD Patients, PD Recipients or PD Deaths. The O/E ratio of PD Recipients significantly correlated with the numbers of hospitals and physicians per person. CONCLUSION: PD Patients and PD Recipients were included in number of people with PD and PD Deaths was derived from people with PD. However, these statistics do not necessarily reflect the prevalence of PD in each prefecture. When using these published statistics as an indicator of the prevalence of PD, it is necessary to clarify the purpose of their use and to comprehend their characteristics.     

Accuracy of asthma death statistics in Australia

Abstract: Asthma mortality statistics issued by the Australian Bureau of Statistics (ABS) were compared with clinical data from a survey of asthma mortality. Deaths in Victoria from May 1986 to April 1987 containing ‘asthma’ in Parts 1 or 2 of the death certificate (N = 405) were reviewed. For each subject, the cause of death attributed by the Victorian Asthma Mortality Survey was compared with the ABS cause of death, by age and sex of the subject. Information on 393 of the 405 deaths investigated by the the Victorian Asthma Mortality Survey was analysed. The ABS estimate of the total number of asthma deaths in Victoria was 47 per cent higher than the estimate of the Victorian Asthma Mortality Survey. In subjects under 50 years of age the two estimates were within 10 per cent. The difference between the estimates increased with age at death for persons over 50 years old and was equivalent for males and females. If the assessment by the Victorian Asthma Mortality Survey of the number of deaths due to asthma is accepted as accurate, then the ABS estimate of asthma deaths was reliable for those under 50 years of age. In those who died at an older age, the ABS significantly overestimated the number of deaths due to asthma in Victoria.     

The mortality risks of smokers in Taiwan: Part I: cause-specific mortality

BACKGROUND: Few studies of adverse health effects from smoking have been conducted in southeastern Asian populations which may exhibit racial, cultural, and smoking behavioral differences that could affect mortality patterns. This study aims to quantify cause-specific mortality risks among cigarette smokers in Taiwan. METHODS: The study population for this investigation was derived from two existing prospective study cohorts: a community-based cohort and a cohort composed of civil servants and teachers. Smoking data were obtained by face-to-face interview in the community cohort and by self-administered questionnaire in the civil servant/teacher cohort. The mortality risks of current smokers, adjusted for age, were compared to those of nonsmokers using Cox's proportional hazards model and dose-response relationships were examined by variables of smoking intensity and duration. RESULTS: Male smokers had significantly higher all-cause mortality than nonsmokers. Cigarette smoking was also significantly associated with increased risks of dying from cancer, cardiovascular disease, respiratory disease, chronic bronchitis, diabetes, peptic ulcer, liver cirrhosis, and kidney disease. In addition, smokers had an increase in risk of fatal injuries from motor vehicle accidents and nonmotor vehicle accidents, as well as cancers of the oral cavity nasopharynx, esophagus, stomach, rectum, liver, and lungs. Risks for women smokers were generally higher than those for men, although this is based on small numbers of smokers. In women, deaths from all causes, all cancers, and cancers of the cervix, liver, and lung, cardiovascular disease, and respiratory disease were also significantly increased. The mean age at death for smokers who died before age 65 from smoking-related diseases was 57.4 years, which represented a loss of 22 years of life expectancy. CONCLUSIONS: The pervasive and serious impact of cigarette smoking on the health of Taiwanese cannot be underestimated.     

The effect of inaccuracies in death certification and coding practices in the European Economic Community (EEC) on international cancer mortality statistics

An investigation into the effect of national death certification and coding practices on published mortality statistics in eight EEC countries is reported. Doctors in each country were asked to complete specimen death certificates for a bank of written case histories. Certificates from each country were coded by their own offices and then by a WHO reference centre. Within and between countries, discrepancies occurred both in the doctors' diagnoses and in the codes assigned to certificates. At an international level these differences had serious implications for the comparability of mortality data for cancers of the cervix and uterus, and for mesotheliomas.     

The effects of economic instability on infant, neonatal, and postneonatal mortality rates: evidence from Taiwan

This paper uses a panel data set comprising 23 cities for the years 1979-2002 in Taiwan and a fixed-effects model to find evidence of the effect of economic instability on infant, neonatal, and postneonatal mortality rates. In addition, the effects of income, demographic factors, and the availability of medical resources are also examined in relation to the mortalities. The most important finding is that infant, neonatal, and postneonatal mortality rates move counter-cyclically with the city unemployment rate in Taiwan. The provision of national health insurance is also found to have a positive impact on the health of infants in Taiwan. Finally, the impact of economic instability on the infant, neonatal, and postneonatal mortality rates is found to be the strongest in the eastern part of Taiwan, which is the region with the fewest health care resources. The analysis provides evidence of the effects of economic instability on the infant, neonatal, and postneonatal mortality rates in a developing country, which are comparable to those of other countries and may provide some important insights into this issue.     

A population-based study on the immediate and prolonged effects of the 1999 Taiwan earthquake on mortality

PURPOSE: To investigate the patterns of immediate seismic deaths and post-earthquake mortality changes in the disaster area after the September 21, 1999 Taiwan earthquake. METHODS: We used the data of 1826 seismic deaths to elucidate the immediate seismic effects on mortality patterns, and to determine the association between seismic death rates and house damage among 23 townships in the disaster area. We used standardized mortality ratios (SMRs) to estimate the changes in mortality of all natural causes (ICD-9: 1-799) in the 12 months after the earthquake. RESULTS: For the 1826 seismic deaths, two leading causes of death were asphyxiation and intracranial injury and the death rates were higher among the female and elderly population. Township-specific seismic death rates were proportional to the proportion of completely collapsed houses. SMRs decreased six months after the earthquake for all residents and female adults aged 45 years and over. CONCLUSIONS: The immediate effects of the Taiwan earthquake included a higher proportion of female and elderly seismic deaths and an association between seismic death rates and earthquake damages in the disaster area. The prolonged effect of the earthquake on mortality in the post-earthquake year was a decrease in mortality for all residents except male adults.