ABSTRACT
The average age of infant deaths, a10, and the average number of years lived-in the age interval-by those dying between ages 1 and 5, a41, are important quantities allowing the construction of any life table including these ages. In many applications, the direct calculation of these parameters is not possible, so they are estimated using the infant mortality rate-or the death rate from 0 to 1-as a predictor. Existing methods are general approximations that do not consider the full variability in the age patterns of mortality below the age of 5. However, at the same level of mortality, under-five deaths can be more or less concentrated during the first weeks and months of life, thus resulting in very different values of a10 and a41. This article proposes an indirect estimation of these parameters by using a recently developed model of under-five mortality and taking advantage of a new, comprehensive database by detailed age-which is used for validation. The model adapts to a variety of inputs (e.g., rates, probabilities, or the proportion of deaths by sex or for both sexes combined), providing more flexibility for the users and increasing the precision of the estimates. This fresh perspective consolidates a new method that outperforms all previous approaches.
Subject(s)
Infant Mortality , Life Tables , Humans , Infant , Female , Male , Child, Preschool , Infant Mortality/trends , Models, Statistical , Infant, Newborn , Life Expectancy/trends , Child Mortality/trends , Age FactorsABSTRACT
INTRODUCTION: Infant and neonatal mortality estimates are typically derived from retrospective birth histories collected through surveys in countries with unreliable civil registration and vital statistics systems. Yet such data are subject to biases, including under-reporting of deaths and age misreporting, which impact mortality estimates. Prospective population-based cohort studies are an underutilized data source for mortality estimation that may offer strengths that avoid biases. METHODS: We conducted a secondary analysis of data from the Child Health Epidemiology Reference Group, including 11 population-based pregnancy or birth cohort studies, to evaluate the appropriateness of vital event data for mortality estimation. Analyses were descriptive, summarizing study designs, populations, protocols, and internal checks to assess their impact on data quality. We calculated infant and neonatal morality rates and compared patterns with Demographic and Health Survey (DHS) data. RESULTS: Studies yielded 71,760 pregnant women and 85,095 live births. Specific field protocols, especially pregnancy enrollment, limited exclusion criteria, and frequent follow-up visits after delivery, led to higher birth outcome ascertainment and fewer missing deaths. Most studies had low follow-up loss in pregnancy and the first month with little evidence of date heaping. Among studies in Asia and Latin America, neonatal mortality rates (NMR) were similar to DHS, while several studies in Sub-Saharan Africa had lower NMRs than DHS. Infant mortality varied by study and region between sources. CONCLUSIONS: Prospective, population-based cohort studies following rigorous protocols can yield high-quality vital event data to improve characterization of detailed mortality patterns of infants in low- and middle-income countries, especially in the early neonatal period where mortality risk is highest and changes rapidly.
Subject(s)
Infant Mortality , Perinatal Death , Infant , Infant, Newborn , Child , Humans , Female , Pregnancy , Latin America/epidemiology , Prospective Studies , Retrospective Studies , Africa South of the Sahara , Asia/epidemiologyABSTRACT
The migrant mortality advantage (MMA) has been observed in many immigrant-receiving countries, but its underlying factors remain poorly understood. This article examines the role of return migration selection effects in explaining the MMA among males aged 65+ using a rich, unique dataset from France. This dataset contains information on native-born and foreign-born pensioners who are tracked worldwide until they die, providing a rare opportunity to assess return migration selection effects and their impact on the MMA. Results provide evidence of substantial and systematic negative return migration selection among foreign-born males in France. Old-age returns, in particular, appear particularly affected by such selection; however, they are not frequent enough to explain the MMA at ages 65+. By contrast, returns at younger ages are much more frequent, and the MMA at ages 65+ essentially disappears once these earlier returns are considered. This study extends the literature on negative selection at return and its impact on the MMA by providing evidence that such negative selection may operate not only at older ages but throughout the life course, with impacts on the MMA that are larger than previously suggested.
Subject(s)
Emigrants and Immigrants , Transients and Migrants , Male , Humans , Emigration and Immigration , France/epidemiology , PensionsABSTRACT
BACKGROUND: The mortality pattern from birth to age five is known to vary by underlying cause of mortality, which has been documented in multiple instances. Many countries without high functioning vital registration systems could benefit from estimates of age- and cause-specific mortality to inform health programming, however, to date the causes of under-five death have only been described for broad age categories such as for neonates (0-27 days), infants (0-11 months), and children age 12-59 months. METHODS: We adapt the log quadratic model to mortality patterns for children under five to all-cause child mortality and then to age- and cause-specific mortality (U5ACSM). We apply these methods to empirical sample registration system mortality data in China from 1996 to 2015. Based on these empirical data, we simulate probabilities of mortality in the case when the true relationships between age and mortality by cause are known. RESULTS: We estimate U5ACSM within 0.1-0.7 deaths per 1000 livebirths in hold out strata for life tables constructed from the China sample registration system, representing considerable improvement compared to an error of 1.2 per 1000 livebirths using a standard approach. This improved prediction error for U5ACSM is consistently demonstrated for all-cause as well as pneumonia- and injury-specific mortality. We also consistently identified cause-specific mortality patterns in simulated mortality scenarios. CONCLUSION: The log quadratic model is a significant improvement over the standard approach for deriving U5ACSM based on both simulation and empirical results.
Subject(s)
Child Mortality , Infant Mortality , Cause of Death , Child , Child, Preschool , China/epidemiology , Humans , Infant , Infant, Newborn , Life TablesABSTRACT
Information about how the risk of death varies with age within the 0-5 age range represents critical evidence for guiding health policy. This study proposes a new model for summarizing regularities about how under-5 mortality is distributed by detailed age. The model is based on a newly compiled database that contains under-5 mortality information by detailed age in countries with high-quality vital registration systems, covering a wide array of mortality levels and patterns. It uses a log-quadratic approach in predicting a full mortality schedule between ages 0 and 5 on the basis of only one or two parameters. With its larger number of age-groups, the proposed model offers greater flexibility than existing models in terms of both entry parameters and model outcomes. We present applications of this model for evaluating and correcting under-5 mortality information by detailed age in countries with problematic mortality data.
Subject(s)
Data Accuracy , Mortality , Child, Preschool , Data Collection , Databases, Factual , Humans , Infant , Infant, NewbornABSTRACT
International migration has increased since 1990, with increasing numbers of migrants originating from low- and middle-income countries (LMICs). Efforts to explain this compositional shift have focused on wage gaps and other push and pull factors but have not adequately considered the role of demographic factors. In many LMICs, child mortality has fallen without commensurate economic growth and amid high fertility. This combination increases young adult populations and is associated with greater outmigration: in the poorest countries, we estimate that a one-percentage-point increase in the five-year lagged growth rate of the population of 15-24-year-olds was associated with a 15 per cent increase in all-age outmigrants, controlling for other factors. Increases in growth of young adult populations led to 20.4 million additional outmigrants across 80 countries between 1990 and 2015. Understanding the determinants of these migration shifts should help policymakers in origin and destination countries to maximize their potential positive effects.
Subject(s)
Emigration and Immigration , Income , Child , Demography , Developing Countries , Humans , Population Dynamics , Socioeconomic Factors , Young AdultABSTRACT
BACKGROUND: Within Europe, France stands out as a major country that lacks recent and reliable evidence on how infant mortality levels vary among the native-born children of immigrants compared with the native-born children of two parents born in France. METHODS: We used a nationally representative socio-demographic panel consisting of 296 400 births and 980 infant deaths for the period 2008-17. Children of immigrants were defined as being born to at least one parent born abroad and their infant mortality was compared with that of children born to two parents born in France. We first calculated infant mortality rates per 1000 live births. Then, using multi-level logit models, we calculated odds ratios of infant mortality in a series of models adjusting progressively for parental origins (M1), core demographic factors (M2), father's socio-professional category (M3) and area-level urbanicity and deprivation score (M4). RESULTS: We documented a substantial amount of excess infant mortality among those children born to at least one parent from Eastern Europe, Northern Africa, Western Africa, Other Sub-Saharan Africa and the Americas, with variation among specific origin countries belonging to these groups. In most of these cases, the excess infant mortality levels persisted after adjusting for all individual-level and area-level factors. CONCLUSIONS: Our findings, which can directly inform national public health policy, reaffirm the persistence of longstanding inequality in infant mortality according to parental origins in France and add to a growing body of evidence documenting excess infant mortality among the children of immigrants in Europe.
Subject(s)
Emigrants and Immigrants , Population Groups , Africa South of the Sahara , Africa, Northern , Africa, Western , Child , Europe/epidemiology , Europe, Eastern , France/epidemiology , Humans , Infant , Infant MortalityABSTRACT
BACKGROUND: Healthy life years have superseded life expectancy (LE) as the most important indicator for population health. The most common approach to separate the total number of life years into those spent in good and poor health is the Sullivan method which incorporates the health dimension to the classic period life table, thus transforming the LE indicator into the health expectancy (HE) indicator. However, life years derived from a period life table and health prevalence derived from survey data are based on different conceptual frameworks. METHOD: We modify the Sullivan method by combining the health prevalence data with the conceptually better fitting cross-sectional average length of life (CAL). We refer to this alternative HE indicator as the "cross-sectional average length of healthy life" (HCAL). We compare results from this alternative indicator with the conventional Sullivan approach for nine European countries. The analyses are based on EU-SILC data in three empirical applications, including the absolute and relative level of healthy life years, changes between 2008 and 2014, and the extent of the gender gap. RESULTS: HCAL and conventional HE differ in each of these empirical applications. In general, HCAL provides larger gains in healthy life years in recent years, but at the same time greater declines in the proportion of healthy life years. Regarding the gender gap, HCAL provides a more favourable picture for women compared to conventional HE. Nonetheless, the extent of these differences between the indicators is only of minor extent. CONCLUSIONS: Albeit the differences between HE and HCAL are small, we found some empirical examples in which the two indicators led to different conclusions. It is important to note, however, that the measurement of health and the data quality are much more important for the healthy life years indicator than the choice of the variant of the Sullivan method. Nonetheless, we suggest to use HCAL in addition to HE whenever possible because it widens the spectrum of empirical analyses and serves for verification of results based on the highly sensitive HE indicator.
Subject(s)
Health Status , Mortality , Adolescent , Adult , Aged , Aged, 80 and over , Algorithms , Child , Child, Preschool , Cross-Sectional Studies , Europe , Female , Humans , Life Expectancy , Male , Middle Aged , Young AdultABSTRACT
BACKGROUND: The migrant mortality advantage is generally interpreted as reflecting the selection of atypically healthy individuals from the country of origin followed by the wearing off of selection effects over time, a process theorised to be accelerated by progressive and negative acculturation in the host country. However, studies examining how migrant mortality evolves over duration of stay, which could provide insight into these two processes, are relatively scarce. Additionally, they have paid little attention to gender-specific patterns and the confounding effect of age. In this study, we analyze all-cause mortality according to duration of stay among male and female migrants in France, with a particular focus on the role of age in explaining duration of stay effects. METHODS: We use the Échantillon Démographique Permanent (Permanent Demographic Sample; EDP), France's largest socio-demographic panel and a representative 1% sample of its population. Mortality was followed-up from 2004 to 2014, and parametric survival models were fitted for males and females to study variation in all-cause mortality among migrants over duration of stay. Estimates were adjusted for age, duration of stay, year, education level and marital status. Duration of stay patterns were examined for both open-ended and fixed age groups. RESULTS: We observe a migrant mortality advantage, which is most pronounced among recent arrivals and converges towards the mortality level of natives with duration of stay. We show this pattern to be robust to the confounding effect of age and find the pattern to be consistent among males and females. CONCLUSIONS: Our novel findings show an intrinsic pattern of convergence of migrant mortality towards native-born mortality over time spent in France, independent from the ages at which mortality is measured. The consistent pattern in both genders suggests that males and females experience the same processes associated with generating the migrant mortality advantage. These patterns adhere to the selection-acculturation hypothesis and raise serious concerns about the erosion of migrant health capital with increasing exposure to conditions in France.
Subject(s)
Acculturation , Mortality/trends , Transients and Migrants/statistics & numerical data , Aged , Female , France/epidemiology , Humans , Male , Middle Aged , Time FactorsABSTRACT
Cohort life expectancy is an important but rarely used indicator of mean longevity. In this paper, we show that there are specific advantages in lagging this indicator in time by its own value, an approach termed Lagged Cohort Life Expectancy (LCLE). We discuss the usefulness of LCLE as an indicator for tracking progress in mean longevity and introduce a new interpretation of LCLE as a reference age separating 'early' deaths from 'late' deaths, or, equivalently, as the age above which individuals in a population can be considered 'above-average' survivors. Using data from 15 countries in the Human Mortality Database, we show that current LCLE can be estimated with a relatively high degree of certainty, at least in these low-mortality populations. Results shed new light on levels and trends in mean longevity in these populations.
Subject(s)
Global Health , Life Expectancy/trends , Longevity , Mortality/trends , Cause of Death , Cohort Studies , Humans , Models, StatisticalABSTRACT
BACKGROUND: France has a large population of second-generation immigrants (i.e., native-born children of immigrants) who are known to experience important socioeconomic disparities by country of origin. The extent to which they also experience disparities in mortality, however, has not been previously examined. METHODS: We used a nationally representative sample of individuals 18 to 64 years old in 1999 with mortality follow-up via linked death records until 2010. We compared mortality levels for second-generation immigrants with their first-generation counterparts and with the reference (neither first- nor second-generation) population using mortality hazard ratios as well as probabilities of dying between age 18 and 65. We also adjusted hazard ratios using educational attainment reported at baseline. RESULTS: We found a large amount of excess mortality among second-generation males of North African origin compared to the reference population with no migrant background. This excess mortality was not present among second-generation males of southern European origin, for whom we instead found a mortality advantage, nor among North African-origin males of the first-generation. This excess mortality remained large and significant after adjusting for educational attainment. CONTRIBUTION: In these first estimates of mortality among second-generation immigrants in France, males of North African origin stood out as a subgroup experiencing a large amount of excess mortality. This finding adds a public health dimension to the various disadvantages already documented for this subgroup. Overall, our results highlight the importance of second-generation status as a significant and previously unknown source of health disparity in France.
ABSTRACT
BACKGROUND: While the health crisis in the former USSR has been well-documented in the case of Russia and other northern former Soviet republics, little is known about countries located in the southern tier of the region, i.e., the Caucasus and Central Asia. OBJECTIVE: This paper presents new mortality information from two Caucasian countries, Georgia and Armenia. Results are compared with information from two relevant countries previously examined in the literature, Kyrgyzstan and Russia. METHODS: Using official statistics (with adjustments when necessary), we compare adult mortality patterns in the four countries since 1979, for all causes and by cause for the recent period. For Kyrgyzstan results are presented by ethnicity, as its mortality levels have been impacted by its large Slavic population. RESULTS: Adult mortality patterns in Armenia and Georgia have been more favorable than in Russia. This appears to be due to a large extent to lower mortality from alcohol-related causes. Mortality patterns in these Caucasian republics resemble those observed in Kyrgyzstan, especially when considering the native portion of the population. CONCLUSIONS: As far as mortality is concerned, Armenia and Georgia have weathered the collapse of the Soviet Union better than Russia. These results document a distinct southern tier pattern of adult mortality in the former Soviet Union. CONTRIBUTION: This article enriches our understanding of the health crisis in the former Soviet Union by bringing new information from two lesser-known countries and further documenting the scale of heterogeneity in mortality experiences across this vast region.
ABSTRACT
BACKGROUND: The clinic era of composite tissue allotransplantation was inaugurated by hand allotransplantation in 1998, giving rise to many controversies and scepticism because of the lifelong immunosuppression, the unclear risk-benefit ratio, and the uncertain long-term functional results of the procedure. The aim of this study was to evaluate the outcomes and the risk/benefit balance in bilateral hand allotransplantation. METHODS: The study included 5 cases of bilateral hand allotransplantation performed in a single center, with a follow-up ranging from 3 to 13 years. The recipients (4 men, 1 woman) were young. The level of amputation was distal in all cases except for 2 patients amputated at the midforearm level. All the recipients initially received the same immunosuppressive treatment that included tacrolimus, mycophenolate mofetil, prednisone, and, for induction, antithymocyte globulins. RESULTS: Patient and graft survival was 100%. All recipients showed adequate sensorimotor recovery (protective and tactile sensitivity and partial recovery of intrinsic muscles), they were able to perform the majority of activities of daily living, and had a normal social life. Most complications occurred in the first posttransplant year and were successfully managed. All recipients experienced at least 1 episode of acute rejection, which was easily reversed by increasing oral steroid dose or by intravenous steroids, except for patient 3, who presented 6 episodes of acute rejection, the latest 2 treated with Campath-1H. CONCLUSIONS: Although bilateral hand transplantation may be a satisfactory treatment option for amputees, a careful selection of candidates and a rigorous evaluation of recipients after transplantation are imperative.
Subject(s)
Hand Transplantation , Activities of Daily Living , Antilymphocyte Serum/therapeutic use , Female , Follow-Up Studies , Graft Rejection/prevention & control , Graft Survival , Hand Strength , Hand Transplantation/adverse effects , Hand Transplantation/methods , Humans , Immunosuppressive Agents/therapeutic use , Male , Mycophenolic Acid/analogs & derivatives , Mycophenolic Acid/therapeutic use , Patient Satisfaction , Prednisone/therapeutic use , Recovery of Function , Risk Assessment , Tacrolimus/therapeutic use , Touch , Transplantation, HomologousABSTRACT
Period life expectancies are commonly used to compare populations, but these correspond to simple juxtapositions of current mortality levels. In order to construct life expectancies for cohorts, a complete historical series of mortality rates is needed, and these are available for only a subset of developed countries. The truncated cross-sectional average length of life (TCAL) is a new measure that captures historical information about all cohorts present at a given moment and is not limited to countries with complete cohort mortality data. The value of TCAL depends on the rates used to complete the cohort series, but differences between TCALs of two populations remain similar irrespective of the data used to complete the cohort series. This result is illustrated by a comparison of TCALs for the US with those for Denmark, Japan, and other high-longevity countries. Specific cohorts that account for most of the disparity in mortality between the populations are identified.
Subject(s)
Life Expectancy , Longevity , Mortality , Adolescent , Adult , Age Factors , Aged , Aged, 80 and over , Child , Child, Preschool , Cross-Sectional Studies , Humans , Infant , Middle Aged , Mortality/trends , Population Dynamics , Young AdultABSTRACT
INTRODUCTION: Estimates for cause-specific mortality for neonates are generally available for all countries for neonates overall (0 to 28 days). However, cause-specific mortality is generally not being estimated at higher age resolution for neonates, despite evidence of heterogeneity in the causes of deaths during this period. We aimed to use the adapted log quadratic model in a setting where verbal autopsy was the primary means of determining cause of death. METHODS: We examined the timing and causes of death among a cohort of neonates in rural Nepal followed as part of the Nepal Oil Massage Study (NOMS). We adapted methods defined by Wilmoth et al (2012) and Guillot et al. (2022) to estimate age and cause-specific mortality among neonates. We used cross validation to estimate the accuracy of this model, holding out each three month period. We took the average cross validation across hold out as our measure of model performance and compared to a standard approach which did not account for the heterogeneity in cause-specific mortality rate within this age group. RESULTS: There were 957 neonates in the NOMS cohort with known age and cause of death. We estimated an average cross-validation error of 0.9 per 1000 live births for mortality due to prematurity in the first week, and 1.1 for mortality due to birth asphyxia, compared to the standard approach, having error 7.4 and 7.8 per 1000 live births, respectively. Generally mortality rates for less common causes such as congenital malformations and pneumonia were estimated with higher cross-validation error. CONCLUSIONS: The stability and precision of these estimates compare favorably with similar estimates developed with higher quality cause-specific mortality surveillance from China, demonstrating that reliably estimating causes of mortality at high resolution is possible for neonates in low resources areas.
Subject(s)
Cause of Death , Infant Mortality , Humans , Infant, Newborn , Nepal/epidemiology , Female , Male , Age Factors , Infant , Models, StatisticalABSTRACT
There is a great deal of uncertainty over the levels of, and trends in, infant mortality in the former Soviet republics of Central Asia. As a result, the impact of the break-up of the Soviet Union on infant mortality in the region is not known, and proper monitoring of mortality levels is impaired. In this paper, a variety of data sources and methods are used to assess levels of infant mortality and their trend over time in one Central Asian republic, Kyrgyzstan, between 1980 and 2010. An abrupt halt to an already established decline in infant mortality was observed to occur during the decade following the break-up of the Soviet Union, contradicting the official statistics based on vital registration. Infants of Central Asian ethnicity and those born in rural areas were also considerably more at risk of mortality than suggested by the official sources. We discuss the implications of these findings, both for health policy in this seldom studied part of the former Soviet Union and for our understanding of the health crisis which it currently faces.
Subject(s)
Infant Mortality/trends , Demography , Humans , Infant , Kyrgyzstan/epidemiology , Life Expectancy/trends , USSRABSTRACT
INTRODUCTION: Countries without complete civil registration and vital statistics systems rely on retrospective full pregnancy history surveys (FPH) to estimate incidence of pregnancy and mortality outcomes, including stillbirth and neonatal death. Yet surveys are subject to biases that impact demographic estimates, and few studies have quantified these effects. We compare data from an FPH vs. prospective records from a population-based cohort to estimate validity for maternal recall of live births, stillbirths, and neonatal deaths in a rural population in Sarlahi District, Nepal. METHODS: We used prospective data, collected through frequent visits of women from early pregnancy through the neonatal period, from a population-based randomized trial spanning 2010-2017. We randomly selected 76 trial participants from three pregnancy outcome groups: live birth (n = 26), stillbirth (n = 25), or neonatal death (n = 25). Data collectors administered the Nepal 2016 Demographic and Health Surveys (DHS)-VII pregnancy history survey between October 22, 2021, and November 18, 2021. We compared total pregnancy outcomes and numbers of pregnancy and neonatal outcomes between the two data sources. We matched pregnancy outcomes dates in the two sources within ± 30 days and calculated measures of validity for adverse outcomes. RESULTS: Among 76 participants, we recorded 122 pregnancy outcomes in the prospective data and 104 outcomes in the FPH within ± 30 days of each woman's total observation period in the trial. Among 226 outcomes, we observed 65 live births that survived to 28 days, 25 stillbirths, and 32 live births followed by neonatal death in the prospective data and participants reported 63 live births that survived to 28 days, 15 stillbirths, and 26 live births followed by neonatal death in the pregnancy history survey. Sixty-two FPH outcomes were matched by date within ± 30 days to an outcome in prospective data. Stillbirth, neonatal death, higher parity, and delivery at a health facility were associated with likelihood of a non-matched pregnancy outcome. CONCLUSIONS: Stillbirth and neonatal deaths were underestimated overall by the FPH, potentially underestimating the burden of mortality in this population. There is a need to develop tools to reduce or adjust for biases and errors in retrospective surveys to improve reporting of pregnancy and mortality outcomes.
Subject(s)
Perinatal Death , Stillbirth , Infant, Newborn , Pregnancy , Female , Humans , Stillbirth/epidemiology , Infant Mortality , Rural Population , Nepal/epidemiology , Reproductive History , Prospective Studies , Retrospective StudiesABSTRACT
BACKGROUND: The under-five mortality rate (the probability of dying between birth and age 5 y, also denoted in the literature as U5MR and (5)q(0)) is a key indicator of child health, but it conceals important information about how this mortality is distributed by age. One important distinction is what amount of the under-five mortality occurs below age 1 y ((1)q(0)) versus at age 1 y and above ((4)q(1)). However, in many country settings, this distinction is often difficult to establish because of various types of data errors. As a result, it is common practice to resort to model age patterns to estimate (1)q(0) and (4)q(1) on the basis of an observed value of (5)q(0). The most commonly used model age patterns for this purpose are the Coale and Demeny and the United Nations systems. Since the development of these models, many additional sources of data for under-five mortality have become available, making possible a general evaluation of age patterns of infant and child mortality. In this paper, we do a systematic comparison of empirical values of (1)q(0) and (4)q(1) against model age patterns, and discuss whether observed deviations are due to data errors, or whether they reflect true epidemiological patterns not addressed in existing model life tables. METHODS AND FINDINGS: We used vital registration data from the Human Mortality Database, sample survey data from the World Fertility Survey and Demographic and Health Surveys programs, and data from Demographic Surveillance Systems. For each of these data sources, we compared empirical combinations of (1)q(0) and (4)q(1) against combinations provided by Coale and Demeny and United Nations model age patterns. We found that, on the whole, empirical values fall relatively well within the range provided by these models, but we also found important exceptions. Sub-Saharan African countries have a tendency to exhibit high values of (4)q(1) relative to (1)q(0), a pattern that appears to arise for the most part from true epidemiological causes. While this pattern is well known in the case of western Africa, we observed that it is more widespread than commonly thought. We also found that the emergence of HIV/AIDS, while perhaps contributing to high relative values of (4)q(1), does not appear to have substantially modified preexisting patterns. We also identified a small number of countries scattered in different parts of the world that exhibit unusually low values of (4)q(1) relative to (1)q(0), a pattern that is not likely to arise merely from data errors. Finally, we illustrate that it is relatively common for populations to experience changes in age patterns of infant and child mortality as they experience a decline in mortality. CONCLUSIONS: Existing models do not appear to cover the entire range of epidemiological situations and trajectories. Therefore, model life tables should be used with caution for estimating (1)q(0) and (4)q(1) on the basis of (5)q(0). Moreover, this model-based estimation procedure assumes that the input value of (5)q(0) is correct, which may not always be warranted, especially in the case of survey data. A systematic evaluation of data errors in sample surveys and their impact on age patterns of (1)q(0) and (4)q(1) is urgently needed, along with the development of model age patterns of under-five mortality that would cover a wider range of epidemiological situations and trajectories. Please see later in the article for the Editors' Summary.