statistical annex explanatory notes 153 uncertainty around under-five and adult mortality rates was considerable because of a aucity of survey or surveillance information, wide distributions were sampled but the results were constrained based on estimates of the maximum and minimum plausible values for the point estimate For 55 countries, mainly in sub-Saharan Africa, estimates of life tables were made by constructing counterfactual life tables excluding the mortality impact of the Hiv/ AIDS epidemic and then combining these life tables with exogenous estimates of the excess mortality rates attributable to HIvIAIDS. The estimates were based on back-calculation models developed as part of collaborative efforts between WHO and the Joint United Nations Programme on HIV/AIDS (UNAIDS)to derive country-level epidemiological estimates for HIV/AIDS. In countries with substantial numbers of deaths, estimates of their uncertainty range were also incorporated into the life table uncertainty analysis. ANNEX TABLE 2A Estimates of child mortality are regularly published by various international organiza- tions, including WHO. Footnotes are used to explain the underlying methodology and sometimes include information on the availability of empirical data that underlie the estimates More frequently, however, the reader of the tables is not informed about the source of information. In the current set of tables WHo has made a first attempt to share a brief summary of the underlying empirical information. This should allow the reader to obtain an idea of how much the estimate is based on real data versus assumptions. At this point the tables do not include an assessment of the quality of the data. The estimation process does take the quality of the empirical data into account In the context of the Millennium Development Goals(MDGs), particular attention is paid to the measurement of progress towards reaching Goal 4, to reduce by two thirds the mortality rate among children under five between 1990 and 2015.At coun try level this implies government commitment not only to implement initiatives to improve child health but also to set up a reliable system to monitor such progress Such a system, if implemented, should be able to provide the number of deaths of children under five years of age by sex, age and cause. However, countries with high levels of child mortality are those where there is very little information or none at all especially on trends Annex Table 2a presents the sources and results of information on under-five mortal- ity rates during the last 25 years which are available at WHO. All efforts were made to ensure completeness and accuracy of the information presented, but the table does not intend to be exhaustive. Data collection efforts are summarized for three periods 1980-1989, 1990-1999 and 2000-2003. Only data collected in the most recent pe riod provide new information on the trend in child mortality in the new millennium. In all other cases, the estimates for the MDGs are drawn entirely from projections based on trends derived from empirical data points prior to the year 2000 There are four primary sources of empirical under-five mortality data: vital reg istration(VR), sample registration system(SRS), surveys and censuses. The vital registration or sample registration system provides numbers of deaths by age and sex obtained by direct observation and reporting of individual deaths. These are pro- spectively collected data. In the case of a survey or a census, the empirical data are based on retrospective data. Interviews with mostly the mother or caregiver or head of household provide information on the survival history of children in the household
statistical annex explanatory notes 153 uncertainty around under-five and adult mortality rates was considerable because of a paucity of survey or surveillance information, wide distributions were sampled but the results were constrained based on estimates of the maximum and minimum plausible values for the point estimates. For 55 countries, mainly in sub-Saharan Africa, estimates of life tables were made by constructing counterfactual life tables excluding the mortality impact of the HIV/ AIDS epidemic and then combining these life tables with exogenous estimates of the excess mortality rates attributable to HIV/AIDS. The estimates were based on back-calculation models developed as part of collaborative efforts between WHO and the Joint United Nations Programme on HIV/AIDS (UNAIDS) to derive country-level epidemiological estimates for HIV/AIDS. In countries with substantial numbers of war deaths, estimates of their uncertainty range were also incorporated into the life table uncertainty analysis. ANNEX TABLE 2A Estimates of child mortality are regularly published by various international organizations, including WHO. Footnotes are used to explain the underlying methodology and sometimes include information on the availability of empirical data that underlie the estimates. More frequently, however, the reader of the tables is not informed about the source of information. In the current set of tables WHO has made a first attempt to share a brief summary of the underlying empirical information. This should allow the reader to obtain an idea of how much the estimate is based on real data versus assumptions. At this point the tables do not include an assessment of the quality of the data. The estimation process does take the quality of the empirical data into account. In the context of the Millennium Development Goals (MDGs), particular attention is paid to the measurement of progress towards reaching Goal 4, “to reduce by two thirds the mortality rate among children under five between 1990 and 2015”. At country level this implies government commitment not only to implement initiatives to improve child health but also to set up a reliable system to monitor such progress. Such a system, if implemented, should be able to provide the number of deaths of children under five years of age by sex, age and cause. However, countries with high levels of child mortality are those where there is very little information or none at all, especially on trends. Annex Table 2a presents the sources and results of information on under-five mortality rates during the last 25 years which are available at WHO. All efforts were made to ensure completeness and accuracy of the information presented, but the table does not intend to be exhaustive. Data collection efforts are summarized for three periods: 1980–1989, 1990–1999 and 2000–2003. Only data collected in the most recent period provide new information on the trend in child mortality in the new millennium. In all other cases, the estimates for the MDGs are drawn entirely from projections based on trends derived from empirical data points prior to the year 2000. There are four primary sources of empirical under-five mortality data: vital registration (VR), sample registration system (SRS), surveys and censuses. The vital registration or sample registration system provides numbers of deaths by age and sex obtained by direct observation and reporting of individual deaths. These are prospectively collected data. In the case of a survey or a census, the empirical data are based on retrospective data. Interviews with mostly the mother or caregiver or head of household provide information on the survival history of children in the household
154 The World Health Report 2005 This may be through gathering mortality information for a specific period prior to the census or survey interview, through a birth history or through questions on children ever born and children still alive("indirect" Brass questions)( 9) The sources of information as listed in the annex table 2a were used to derive the estimated trends and projections of rates for under-five-year-olds for the year 2003 shown in both Annex Tables 1 and 2a. A standard approach to predicting the most recent child mortality was employed to ensure comparability between countries and may lead to minor differences compared with official statistics prepared by Member States(7) For each country, estimates of under-five mortality rate are derived from weighted least squares regression of under-five mortality rate on their reference dates Explanatory variables include date, as well as those that capture rates of change of under-five mortality across periods of time. The weights assigned to each data point eflect its quality or consistency with all other data points. In other cases, additional sources were used as inputs in the standard regression model Vital registration can be considered as the gold standard for the collection of mortality data, as it allows the registration of deaths by age and sex. Vital registration systems with high levels of completeness are commonplace in developed countries. Although several developing countries are improving their vital registration systems, in many other countries-especially countries with high levels of mortality- such a system is non-existent. Another source of mortality data is the sample vital registration system which assesses vital events at the national level from information collected in sample areas. These two sources, in principle, provide data on a regular yearly basis The column"VR/SRS" in Annex Table 2a-vital registration/sample registration system shows the number of years of data from either system available at WHO. In the absence of a prospective data collection system in a country, household surveys will provide direct or indirect estimates of the level of under-five mortality, primarily using birth history questionnaires in which mothers are asked to provide information about their children, those still living as well as those who did not survive. Similarly, census questionnaires may include a module on mortality, which may refer to recent deaths in the household or use "indirect" Brass questions to estimate child mortality. It should be noted that one single survey or census can generate more than one estimate of under-five mortality for different periods of time. However, the Survey/Census column of Annex Table 2a shows the number of the surveys or censuses available at WHO. Furthermore, when a survey was carried over from one year to the next, only the starting year was taken into account It is worth noting the efforts of WHO regional offices in collecting vital registration data from Member States. International agencies such as the United Nations and UNICEF also maintain historical databases on under-five mortality rates, which have been generously shared and incorporated in our analyses. Other sources of informa tion include data from national censuses or surveys, or from specialist surveys such as the Demographic and Health Survey( DHS)undertaken by ORC Macro and the Multiple Indicator Cluster Survey(MICS)conducted by UNICEF. Finally, national statis tical documents such as statistical yearbooks, reports from specialized agencies and periodical paper findings were also incorporated into the database ANNEX TABLE 2B Whereas Annex Table 2a presents the estimates on under-five mortality rates, An nex Table 2b presents an empirical basis of detailed age-specific mortality rates directly obtained from the most readily available sources on the subject, namely
154 The World Health Report 2005 This may be through gathering mortality information for a specific period prior to the census or survey interview, through a birth history or through questions on children ever born and children still alive (“indirect” Brass questions) (9). The sources of information as listed in the Annex Table 2a were used to derive the estimated trends and projections of rates for under-five-year-olds for the year 2003 shown in both Annex Tables 1 and 2a. A standard approach to predicting the most recent child mortality was employed to ensure comparability between countries and may lead to minor differences compared with official statistics prepared by Member States (7). For each country, estimates of under-five mortality rate are derived from weighted least squares regression of under-five mortality rate on their reference dates. Explanatory variables include date, as well as those that capture rates of change of under-five mortality across periods of time. The weights assigned to each data point reflect its quality or consistency with all other data points. In other cases, additional sources were used as inputs in the standard regression model. Vital registration can be considered as the gold standard for the collection of mortality data, as it allows the registration of deaths by age and sex. Vital registration systems with high levels of completeness are commonplace in developed countries. Although several developing countries are improving their vital registration systems, in many other countries – especially countries with high levels of mortality – such a system is non-existent. Another source of mortality data is the sample vital registration system which assesses vital events at the national level from information collected in sample areas. These two sources, in principle, provide data on a regular yearly basis. The column “VR/SRS” in Annex Table 2a – vital registration/sample registration system shows the number of years of data from either system available at WHO. In the absence of a prospective data collection system in a country, household surveys will provide direct or indirect estimates of the level of under-five mortality, primarily using birth history questionnaires in which mothers are asked to provide information about their children, those still living as well as those who did not survive. Similarly, census questionnaires may include a module on mortality, which may refer to recent deaths in the household or use “indirect” Brass questions to estimate child mortality. It should be noted that one single survey or census can generate more than one estimate of under-five mortality for different periods of time. However, the “Survey/Census” column of Annex Table 2a shows the number of the surveys or censuses available at WHO. Furthermore, when a survey was carried over from one year to the next, only the starting year was taken into account. It is worth noting the efforts of WHO regional offices in collecting vital registration data from Member States. International agencies such as the United Nations and UNICEF also maintain historical databases on under-five mortality rates, which have been generously shared and incorporated in our analyses. Other sources of information include data from national censuses or surveys, or from specialist surveys such as the Demographic and Health Survey (DHS) undertaken by ORC Macro and the Multiple Indicator Cluster Survey (MICS) conducted by UNICEF. Finally, national statistical documents such as statistical yearbooks, reports from specialized agencies and periodical paper findings were also incorporated into the database. ANNEX TABLE 2B Whereas Annex Table 2a presents the estimates on under-five mortality rates, Annex Table 2b presents an empirical basis of detailed age-specific mortality rates directly obtained from the most readily available sources on the subject, namely
statistical annex explanatory notes 155 Demographic and Health Survey(DHS)and vital registra- tion(VR). In addition to the familiar breakdown of infants Intervala under the age of one year into neonatal(0-27 days) and 0. Under-five 0-4 years postneonatal(28 days-11 months)periods(10), the latter age 1 0-11 months group was further divided into two intervals, 28 days-5 months 1.1 0-27 days and 6-11 months. Similarly, the child period between the first 1.2 Postneonatal 28 days-11 months and fifth birthday was divided into 12-23 and 24-59 months. 1.2.1 Early postneonatal 28 days-5 months The table here summarizes the definitions of the age break- 1.2.2 Late postneonatal 6-11 months down Child The mortality rates presented in Annex Table 2b are expressed 2.1 12-23 months as the probability of dying during each period, for those who 2.2 Early childhood 24-59 months ave survived until the beginning of that period. Therefore the he upper limit of the interval refers to completed days, months or years totals are not equivalent to the sum of the rates of the compo- nent age groups From DHS raw data sets, UNICEF collaborated in re-analysing them to compute detailed age-specific death rates, following the DHS approach, using synthetic cohort probabilities of death(11). In order to obtain sufficient robustness in the estimates these represent the period of five years prior to the surveys. No adjustments have been made for reporting issues such as heaping in these calculations VR data reported by Member States (1)are the other source where age-specific mortality can be computed, although the current under-one mortality age split that WHO requests does not allow detail within the postneonatal mortality rate. Thus, only neonatal and postneonatal mortality rates are presented in Annex Table 2b. For these two rates, we applied the following formula based on live births(12) Neonatal mortality rate= neonatal deaths/ live births Postneonatal mortality rate=postneonatal deaths /(live births-neonatal deaths) For the other age groups, we applied a standard formula from the abridged lifetable n,M where .1+n(-A)M q, is the probability of dying between exact ages x and X+n; n is the interval of the age group expressed in years; x is the exact age at the beginning of the age group MM is the age-specific death rate of the age group between x and X+n; and n a is the fraction of last age interval of life In this table we relied as much as possible on empirical data; for the denominators (live births and population of age-specific death rates) national data were given priori- ty, otherwise the estimates from the United Nations Population Division were used (3) Comparisons across countries should be made with great caution as the results are not directly comparable since the method of calculation varies depending on sources and there are different degrees of completeness of vital registration data submitted by Member State Those DHS and vR data that can be supplemented by other sources of information would serve as the basis of the analysis between the age groups, by country or by region. This insight into the level of mortality would possibly lead to identification of some cause-specific pattern for a better understanding of the epidemiological transi tion within childhood mortality
statistical annex explanatory notes 155 Demographic and Health Survey (DHS) and vital registration (VR). In addition to the familiar breakdown of infants under the age of one year into neonatal (0–27 days) and postneonatal (28 days–11 months) periods (10), the latter age group was further divided into two intervals, 28 days–5 months and 6–11 months. Similarly, the child period between the first and fifth birthday was divided into 12–23 and 24–59 months. The table here summarizes the definitions of the age breakdown. The mortality rates presented in Annex Table 2b are expressed as the probability of dying during each period, for those who have survived until the beginning of that period. Therefore the totals are not equivalent to the sum of the rates of the component age groups. From DHS raw data sets, UNICEF collaborated in re-analysing them to compute detailed age-specific death rates, following the DHS approach, using synthetic cohort probabilities of death (11). In order to obtain sufficient robustness in the estimates, these represent the period of five years prior to the surveys. No adjustments have been made for reporting issues such as heaping in these calculations. VR data reported by Member States (1) are the other source where age-specific mortality can be computed, although the current under-one mortality age split that WHO requests does not allow detail within the postneonatal mortality rate. Thus, only neonatal and postneonatal mortality rates are presented in Annex Table 2b. For these two rates, we applied the following formula based on live births (12): Neonatal mortality rate = neonatal deaths / live births Postneonatal mortality rate = postneonatal deaths / (live births – neonatal deaths) For the other age groups, we applied a standard formula from the abridged lifetable: where nqx is the probability of dying between exact ages x and x+n; n is the interval of the age group expressed in years; x is the exact age at the beginning of the age group; nMx is the age-specific death rate of the age group between x and x+n; and nax is the fraction of last age interval of life. In this table we relied as much as possible on empirical data; for the denominators (live births and population of age-specific death rates) national data were given priority, otherwise the estimates from the United Nations Population Division were used (3). Comparisons across countries should be made with great caution as the results are not directly comparable since the method of calculation varies depending on sources and there are different degrees of completeness of vital registration data submitted by Member States. Those DHS and VR data that can be supplemented by other sources of information would serve as the basis of the analysis between the age groups, by country or by region. This insight into the level of mortality would possibly lead to identification of some cause-specific pattern for a better understanding of the epidemiological transition within childhood mortality. Definition Intervala 0. Under-five 0–4 years 1. Infant 0–11 months 1.1 Neonatal 0–27 days 1.2 Postneonatal 28 days–11 months 1.2.1 Early postneonatal 28 days–5 months 1.2.2 Late postneonatal 6–11 months 2. Child 1–4 years 2.1 Toddler 12–23 months 2.2 Early childhood 24–59 months a The upper limit of the interval refers to completed days, months or years. nnMx nqx = 1 + n(1–nax ) nMx
156 The World Health Report 2005 ANNEX TABLE 3 Before estimating the number of deaths for individual causes, the first step is to obtain an estimated number of deaths from all causes combined which will constitute an envelope"to make sure that the sum of all cause-specific mortality does not exceed the estimated number of deaths in each country. The envelope itself is derived from the mortality rates from abridged life tables (4, 5) and applying them to the popula tion estimates obtained from the United Nations Population Division (3). The current mortality envelope was based on the joint work by WHO and UNICEF for the period Countries with a sound vital registration system(vR)with a relatively high coverage ould capture the representative pattern of causes of death at the national level. In addition to the levels of coverage, it is important to analyse carefully the quality of the coding pratices which should follow the rules of the International Statistical Clas ification of Diseases and Related Health Problems(ICD)(6, 8, 10 In some countries, improper completion of death certificates or systematic biases in diagnosis are quite For 72 countries where the VR coverage is over 85%, WHO considers VR as the gold standard and uses the pattern directly derived from VR, after adjusting for the ill-defined categories (e. g ICD-9 Chapter XVI, ICD-10 Chapter XVll; unspecified car- diovascular diseases; cancers of unknown sites; unspecified external causes) and checking cause-specific trends for the most recent years available. When estimating death rates for very small countries whereby a small change in the number of deaths substantially affects the overall cause-of-death pattern, an average of the last three years of data from their VR is used to avoid spurious trends In the absence of a Data and methods used for estimating under-five causes of death omplete vital reports/models ge-specific CHERG Incomplete vital mple registration studies, verbal autopsies, WHO programme estimates DHS MICS and mortality UNAIDS other surveys UN estimates timates mortality patterns All-cause mortality nd sex Country level age, specific mortality estimates Global and regi level age, sex and cause-
156 The World Health Report 2005 ANNEX TABLE 3 Before estimating the number of deaths for individual causes, the first step is to obtain an estimated number of deaths from all causes combined, which will constitute an “envelope” to make sure that the sum of all cause-specific mortality does not exceed the estimated number of deaths in each country. The envelope itself is derived from the mortality rates from abridged life tables (4, 5) and applying them to the population estimates obtained from the United Nations Population Division (3). The current mortality envelope was based on the joint work by WHO and UNICEF for the period 1990–2003. Countries with a sound vital registration system (VR) with a relatively high coverage would capture the representative pattern of causes of death at the national level. In addition to the levels of coverage, it is important to analyse carefully the quality of the coding pratices which should follow the rules of the International Statistical Classification of Diseases and Related Health Problems (ICD) (6, 8, 10). In some countries, improper completion of death certificates or systematic biases in diagnosis are quite frequent. For 72 countries where the VR coverage is over 85%, WHO considers VR as the gold standard and uses the pattern directly derived from VR, after adjusting for the ill-defined categories (e.g. ICD-9 Chapter XVI, ICD-10 Chapter XVIII; unspecified cardiovascular diseases; cancers of unknown sites; unspecified external causes) and checking cause-specific trends for the most recent years available. When estimating death rates for very small countries whereby a small change in the number of deaths substantially affects the overall cause-of-death pattern, an average of the last three years of data from their VR is used to avoid spurious trends. In the absence of a Global and regional level age, sex and causespecific mortality estimates Censuses Data and methods used for estimating under-five causes of death DHS, MICS and other surveys UN estimates Age-specific mortality rates Complete vital registration Incomplete vital registration Sample registration system UN population estimates All-cause mortality envelope by age and sex Life tables Independent studies / reports / models CHERG Epidemiological data from studies, verbal autopsies, WHO programme estimates UNAIDS Cause-specific mortality patterns Country level age, sex and causespecific mortality estimates Under-5 and adult mortality rates