Teenage fertility, socioeconomic status and infant mortality

This paper examines the relationship between infant mortality and a complex measure of socioeconomic status for evidence of diminution. In data on counties in the US with a minimum of 20 infant deaths over the 5-year period 1971-75, no evidence of a declining relationship between socioeconomic status and infant mortality was found. Both level of community affluence and racial composition of the population exerted direct effects on levels of infant deaths. In addition, both socioeconomic status and racial composition exhibited indirect effects which operated through teenage childbearing. When total infant mortality was subdivided, teenage fertility serves as a mediating variable in the link between socioeconomic status and neonatal mortality, but not for the postneonatal components. Given the nearly equivalent total effect of socioeconomic status on infant mortality, it is concluded that the classic division into neonatal (supposedly a function of biological and genetic agents) and postneonatal (traditionally attributed to social and environmental agents), may be too crude to allow the contemporary effects of the socioenvironmental milieu to be evaluated effectively.     

Extrinsic Mortality Effects on Reproductive Strategies in a Caribbean Community

Extrinsic mortality is a key influence on organisms’ life history strategies, especially on age at maturity. This historical longitudinal study of 125 women in rural Domenica examines effects of extrinsic mortality on human age at maturity and pace of reproduction. Extrinsic mortality is indicated by local population infant mortality rates during infancy and at maturity between the years 1925 and 2000. Extrinsic mortality shows effects on age at first birth and pace of reproduction among these women. Parish death records show huge historical variation in age-specific mortality rates. The infant mortality rate (IMR) in the early 1920s was low, increased dramatically beginning in 1929, and reached a maximum in the 1950s, at which point IMR declined steadily to its present low rate. The mortality rate early in life showed a quadratic association with age at first birth. Women who experienced conditions of low IMR early in life reproduced relatively late in life. Those born into moderately high levels of infant mortality tended to reproduce earlier than those born at low levels. At very high infant mortality levels early in life, women went on to delay reproduction until relatively late, possibly as a result of somatic depletion and energetic stress associated with the conditions that lead to high IMR. Population mortality rates at age of maturity also showed a quadratic association with age at first birth. The pace of reproduction, estimated as number of surviving offspring controlled for maternal age, showed a similar quadratic effect. There were complex interactions between population mortality rates in infancy and at maturity. When extrinsic mortality was high during infancy, extrinsic mortality later in life had little effect on timing of first birth. When extrinsic mortality was low to moderate in infancy, extrinsic mortality later in life had significant effects on adult reproduction. I speculate that these effects are mediated through development of personality facets associated with reproduction.     

A dynamic framework for the study of optimal birth intervals reveals the importance of sibling competition and mortality risks

Human reproductive patterns have been well studied, but the mechanisms by which physiology, ecology and existing kin interact to affect the life history need quantification. Here, we create a model to investigate how age‐specific interbirth intervals adapt to environmental and intrinsic mortality, and how birth patterns can be shaped by competition and help between siblings. The model provides a flexible framework for studying the processes underlying human reproductive scheduling. We developed a state‐based optimality model to determine age‐dependent and family‐dependent sets of reproductive strategies, including the state of the mother and her offspring. We parameterized the model with realistic mortality curves derived from five human populations. Overall, optimal birth intervals increase until the age of 30 after which they remain relatively constant until the end of the reproductive lifespan. Offspring helping each other does not have much effect on birth intervals. Increasing infant and senescent mortality in different populations decreases interbirth intervals. We show that sibling competition and infant mortality interact to lengthen interbirth intervals. In lower‐mortality populations, intense sibling competition pushes births further apart. Varying the adult risk of mortality alone has no effect on birth intervals between populations; competition between offspring drives the differences in birth intervals only when infant mortality is low. These results are relevant to understanding the demographic transition, because our model predicts that sibling competition becomes an important determinant of optimal interbirth intervals only when mortality is low, as in post‐transition societies. We do not predict that these effects alone can select for menopause.     

The relationship between socioeconomic status and infant mortality in metropolitan Ohio, 1999-2001

Empirical evidence has consistently documented the direct relationship between infant mortality and socioeconomic inequality in the United States and numerous other countries. While the majority of these studies reveal an inverse relationship between socioeconomic level and infant mortality, not even this finding is free from disagreement. Furthermore, the specific nature and magnitude of this relationship has varied over time. This study will examine the relationship between socioeconomic status and infant mortality in metropolitan Ohio by using birth and infant death data centered on the 2000 Census. The analyses presented herein will describe and analyze the relationship between infant mortality and socioeconomic status in metropolitan Ohio in the year 2000. The key finding is that in spite of remarkable declines in infant mortality during the past several decades, most notably in neonatal mortality, there continues to be a pronounced inverse association between the infant death rate and the economic status of a population.     

Patterns and variations in the relationship between infant mortality and socioeconomic status

Abstract

This study utilizes an ecological approach based on census tracts of residence to examine the relationship between infant mortality and socioeconomic status in metropolitan Ohio at two points in time (1959–61 and 1969–71). The data presented clearly indicate that the infant mortality rate continues to exhibit a pronounced inverse association with a wide variety of socio‐economic variables. Although there were some notable exceptions and/or variations from the general patterns, a basic inverse relationship was generally found to be characteristic of both neonatal and postnatal components of infant mortality, for both males and females, and for both major exogenous and endogenous causes of death. Of all the variables examined, the one factor that emerged as the strongest and most consistent determinant of census tract variations in infant mortality was the proportion of low income families. Thus, the overriding conclusion suggested by this study is that in spite of such things as continued advances in medicine and public health, the expansion of a variety of social programs during the 1960's, and the recent resumption of a downward trend in the overall infant mortality rate, there has been little if any progress in achieving more equitable life chances for the economically deprived segments of our population.     

The relationship between socioeconomic status and infant mortality in metropolitan Ohio, 1999–2001

Abstract

Empirical evidence has consistently documented the direct relationship between infant mortality and socioeconomic inequality in the United States and numerous other countries. While the majority of these studies reveal an inverse relationship between socioeconomic level and infant mortality, not even this finding is free from disagreement. Furthermore, the specific nature and magnitude of this relationship has varied over time.

This study will examine the relationship between socioeconomic status and infant mortality in metropolitan Ohio by using birth and infant death data centered on the 2000 Census. The analyses presented herein will describe and analyze the relationship between infant mortality and socioeconomic status in metropolitan Ohio in the year 2000. The key finding is that in spite of remarkable declines in infant mortality during the past several decades, most notably in neonatal mortality, there continues to be a pronounced inverse association between the infant death rate and the economic status of a population.     

Infant and child mortality in Pakistan--some trends and differentials

Data from reproductive histories collected in the Population, Labor Force and Migration Survey (PLM) of 1979 are used to analyze trends and differentials in infant and child mortality in Pakistan. Comparisons with the Pakistan Fertility Survey (PFS) findings are also presented. The main concern is to provide from the latest national data, the PLM, direct measures of infant and child mortality and to demonstrate the relatively static and low chances of survival for children in Pakistan. The apparent trends from the PLM and the PFS are similar and seem to confirm that infant and childhood mortality has ceased to decline, at least rapidly, since 1965-69. Neonatal mortality is higher at levels of 70-85 deaths/1000 compared to postneonatal mortality of 40-60 deaths/1000. Improvements in neonatal rates from 1950 until 1975 are only approximately 1/2 of those for postneonatal rates for that period. The relationship between maternal age and mortality in the PLM data confirms that children of youngest mothers experienced the highest rates of infant mortality; mortality is again higher for children of oldest mothers aged 35 and above. The pattern of mortality in the 2 surveys is similar except that in the PFS there was little variation among births higher than 5th order. Sex differentials in mortality are very clear in both surveys. Boys have higher chances of dying in the 1st month of life but then the probability of their surviving from age 1 to 5 years is higher, reflecting the behavioral preference for the male sex in this society. The data also demonstrate an almost monotonic decline in infant and child mortality associated with longer birth intervals. Childhood mortality shows a less clear association with preceding birth interval than does infant mortality. While neonatal mortality is much higher in rural than in urban areas, there are negligible differences in the postneonatal rate. The urban-rural differential continues into childhood, reflecting lower health care and nutrition of children in rural areas. The data confirm the importance of parental education, particularly that of mothers, as a contributor to the health and mortality of infants. Mortality between age 1 and 5 years for children of the rural educated group is lower than that for the urban uneducated indicating the strong influence that education of mothers can have in preventing child loss. The combined evidence from the PFS and PLM data stresses the importance of improving health facilities in the rural areas, in aneffort to reduce the differences in mortality by area of residence. The data from both surveys also suggest the need to restrict motherhood to between the ages of 20 and 34, when obstetrical and health risks are minimal, and indicate the definite advantages of increasing the spacing between children.     

Modeling human mortality using mixtures of bathtub shaped failure distributions

Aging and mortality is usually modeled by the Gompertz-Makeham distribution, where the mortality rate accelerates with age in adult humans. The resulting parameters are interpreted as the frailty and decrease in vitality with age. This fits well to life data from 'westernized' societies, where the data are accurate, of high resolution, and show the effects of high quality post-natal care. We show, however, that when the data are of lower resolution, and contain considerable structure in the infant mortality, the fit can be poor. Moreover, the Gompertz-Makeham distribution is consistent with neither the force of natural selection, nor the recently identified 'late life mortality deceleration'. Although actuarial models such as the Heligman-Pollard distribution can, in theory, achieve an improved fit, the lack of a closed form for the survival function makes fitting extremely arduous, and the biological interpretation can be lacking. We show, that a mixture, assigning mortality to exogenous or endogenous causes, using the reduced additive and flexible Weibull distributions, models well human mortality over the entire life span. The components of the mixture are asymptotically consistent with the reliability and biological theories of aging. The relative simplicity of the mixture distribution makes feasible a technique where the curvature functions of the corresponding survival and hazard rate functions are used to identify the beginning and the end of various life phases, such as infant mortality, the end of the force of natural selection, and late life mortality deceleration. We illustrate our results with a comparative analysis of Canadian and Indonesian mortality data.     

Factors influencing prereproductive mortality in the isolated and preindustrial western Mediterranean population of La Alpujarra, 1900-1950

We study the effects of several variables on the prereproductive mortality pattern in the isolated and rural population of La Alpujarra, located on the western Mediterranean coast (southeast Spain), in the first half of the 20th century. The study is a retrospective analysis from a total sample of 2,200 deliveries, 2,085 of which were born alive and 171 of which did not survive to the 20th birthday. The potential influences of birthdate of children, twinning, firstborn, parental inbreeding, and sex on Alpujarran mortality were analyzed through logistic regression. Parity, family size, and birth interval effects were estimated through the difference between observed and expected mortality rates. In every case four age groups of mortality were considered because of the large influence of child growth: neonatal (less than 1 month of life), postneonatal infant (between 1 month and 1 year old), childhood (1-5 years old), and youth (5-20 years old). The Alpujarran prereproductive mortality pattern can be summarized as the result of three main risk factors: biodemographic, biomechanical, and social and health determinants. In general, every factor showed a decreased effect as children grew. The most significant determinants were birthdate of children, which is more related to increased mother's awareness of child care than to health improvement, and family size associated with decreasing alimentary resources as the sibling number increased. Male mortality was higher than female mortality in children older than 1 year but not for infant mortality, possibly as a result of a reproductive behavior favorable to males. Although firstborn status and twinning appeared associated with high mortality, maternal age and birth interval were related to low risk, but these influences always ceased after the first month of life. Parental inbreeding did not show any effect on infant, childhood, or youth mortality.     

Infant mortality decline in the late 19th and early 20th centuries: the role of market milk

Starting in the late 19th and early 20th centuries, a precipitous decline in infant mortality was observed in the United States. Economic growth, improved nutrition, new sanitary measures, and advances in knowledge about infant care all contributed to this decline in infant mortality. Little is known, however, about how these individual factors affected disease-specific components of infant mortality over time. Systematic review of historical data suggests that cleaning the market milk supply was the single most important contributor to this decline in both diarrheal and overall infant mortality, and that this development played a far more important role than family income, other sanitary measures, or medical intervention.     

Sex differentials in infant and child mortality in Korea

Abstract

This paper reports on a study of infant and child mortality in the Republic of Korea, a country known for a strong son preference, using the 1974 World Fertility Survey data. When the age‐specific probabilities of dying for ages zero to five are compared for male and female children, an unusual pattern of relatively high female mortality is observed. The higher female mortality is more pronounced during childhood than during infancy. Multivariate analysis of life tables, using a hazard model, shows that covariates influencing the mortality at young ages differ for male and female children and suggests that male and female children receive unequal care by their parents. The analysis also reveals different patterns of interaction between infant and child mortality and mother's fertility control behavior depending on the sex of the child.     

Maternal factors and infant and child mortality in Bangladesh

Using data from The World Fertility Survey, this study shows that the length of the preceding birth interval was the most important maternal factor influencing infant and child mortality risks in Bangladesh. This was such a crucial factor that its effects remain unaltered whether or not the influences of mother's age at birth and birth order are controlled. Infant and child mortality in Bangladesh can be expected to decline considerably if successive births can be spaced by an interval of at least 1.5 years. Child spacing seems to be the major factor requiring program attention. The effects of mother's education and place of residence on infant and child mortality are independent of the effects of maternal age at birth, birth order, and the preceding birth interval. The higher survival chances of children of educated mothers resulted neither through the age at which childbearing started nor through birth spacing but are likely to be related to their smaller family size and to other non-maternal proximate determinants of early mortality.     

Changing determinants of infant and child mortality: on the basis of the Korean experience, 1955-73

Data from the 1974 Korean National Fertility Survey were analyzed to learn more about the main determinants of infant and child mortality in the course of mortality decline and how they change. In the Korean survey, about 5000 eligible women were selected for the individual survey and the sample design aimed at a self-weighting nationally representative and probability sample. Preliminary analysis showed clear mortality differentials between different socioeconomic levels and between demographic subgroups in infant and child mortality during the period 1955-73 in Korea. To examine the net effect of each variable on mortality, the logit-linear model was used. A table shows the probability level of 4 variables -- maternal age, birth order, mother's education, and number of rooms used by household -- in Korea, when the effects of others were controlled. In the urban areas, only the socioeconomic factors were the main determinants of infant mortality on all the birth cohorts. Mother's education and number of rooms used strongly affected infant mortality in the 1955-59 and 1960-64 birth cohorts, but the effects became weaker in the 1965-69 and 1970-73 birth cohorts, and their statistical significance was reduced. In the rural areas, the effects of 3 variables -- the exception being number of rooms used -- on infant mortality were statistically significant. It is concluded that the main determinants of infant mortality in urban areas were socioeconomic factors. The main determinants of infant mortality in the rural areas were demographic in the earlier birth cohorts, but in the recent birth cohorts mother's education, a socioeconomic factor, became the main determinant while the effects of demographic variables became weaker and finally disappeared. The change in the determinants of child mortality appears to be the reverse of that for infant mortality. Prior to the introduction of the national development program, in the rural areas mother's education was the main determinant of child mortality (rural 1955-59 cohort), but with the socioeconomic development the determinants changed to give dominance to demographic factors (urban 1955-59) cohort and, in the recent period, even the effects of demographic factors on child mortality became weaker (urban 1960-69 cohort). When the differences in living status by maternal age were weaker and the competition among siblings less because of small family size, only the socioeconomic variables remained as main determinants affecting child mortality.     

Reproductive parameters of female Japanese macaques: Thirty years data from the arashiyama troops,Japan

Over a 30-year period from 1954 to 1983, 975 live births were recorded for Japanese macaque females at the Iwatayama Monkey Park, Arashiyama, Japan. Excluding unknown birth dates, primiparous mothers gave birth to 185 infants (182 cases with age of mother known) and multiparous mothers gave birth to 723 infants (603 cases with age of mother known). The peak month of birth was May with 52.3% of the total births occurring during the period. Multiparous females who had not given birth the previous year did so earlier than multiparous females who had given birth the previous year and also earlier than primiparous females. Among the females who had given birth the previous year, females whose infant had died gave birth earlier than females who had reared an infant the previous year. The offspring sex ratio (1:0.97) was not significantly different from 1:1, and revealed no consistent association with mother's age. Age-fecundity exhibited a humped curve. The annual birth rate was low at the age of 4 years but increased thereafter, ranging between 46.7% and 69.0%, at between 5 and 19 years of age, but again decreased for females between 20 and 25 years of age. Some old females displayed clear reproductive senescence. The infant mortality within the first year of age was quite low (10.3%) and the neonatal (less than 1 month old) mortality rate accounted for 49.0% of all infant deaths. There was no significant difference between the mortality rates of male and female infants. A female's rank-class had no apparent effect on the annual birth rate, infant mortality, and offspring sex ratio. These long-term data are compared with those from other primate populations.     

Social class as a risk factor for infant mortality in an Australian population

Studies in other countries have identified social class as a risk factor for infant mortality. In Australia there is no systematic collection of population data by social class, partly due to the absence of a recognized measure. The use of occupational prestige as an indicator of social class is discussed and Australian prestige scales reviewed. In a population based study, logistic regression analysis of infant mortality in an Australian (NSW) population shows the effects of social class on infant mortality which remain when maternal age, marital status and parity are controlled.     

Change in immunisation schedule and sudden infant death syndrome in Hungary

Infant mortality in Hungary was higher than in other European countries; however, the reported incidence of sudden infant death syndrome (SIDS) has been lower than those for Western Europe and the United States. Childhood immunisation has been reported to be a protective factor for SIDS. In Britain, the change to an earlier immunisation schedule for diphtheria, pertussis, and tetanus appeared to be associated with a shift in the age distribution of SIDS. In 1999, immunisation for Haemophilus influenzae type b (Hib) was introduced for Hungarian infants at the age of 2 months. Data for total infant mortality and SIDS in Hungary were analysed between 1990 and 2002. Infection was the major cause of death among Hungarian infants followed by SIDS. Following introduction of Hib immunisation, there was a decrease in deaths due to meningitis from an average of 3.5% of all infant deaths between 1990 and 1998 to an average of 1% of all infant deaths between 1999 and 2002 (p=0.00). There was also a significant decrease in the proportion of SIDS in the age range > or =2 months from 48% in the earlier period to 39% after introduction of the vaccine (p=0.03). The decrease in SIDS might be due in part to decrease in unrecognised Hib infections or to induction of antibodies by the tetanus toxoid to which the Hib polysaccharide is conjugated that are cross reactive with bacterial toxins implicated in SIDS.     

Sudden infant death syndrome and the age‐cause proxy relationship in infancy

Abstract

Evidence from a longitudinal study of the relationship between socioeconomic status and infant mortality in metropolitan Ohio is presented in an effort to throw additional light on the continuing debate over the validity of the age‐cause proxy relationship in infancy. The results indicate that while there is a fairly strong and consistent association between neonatal mortality and endogenous causes of death that is little affected by the classification of Sudden Infant Death Syndrome, the nature of the association between postneonatal mortality and exogenous causes of death varies from weak to moderate depending upon where this cause is included. Additional evidence pertaining to the role of SIDS in contributing to the long‐standing inverse association between infant mortality and socioeconomic status is presented, thus further emphasizing the need for continued research to clarify the etiologic mechanisms of this poorly understood condition.     

Factors affecting infant and child mortality

This paper examines the determinants of infant and child mortality variations in Jordan, Yemen, Egypt, and Tunisia using data from WFS surveys. The analysis considers biological correlates of mortality--mother's age, birth order, birth interval, and previous infant loss--and several social factors--mother's and father's education, mother's residence, father's occupation, and mother's work experience since marriage. The estimates for the 4 countries show large variations in the mortality rates and an expected pattern of declining infant and child mortality during the period of 20 years prior to the survey. Further, the proportionate decline in child mortality in each country was generally greater than the proportionate decline in infant mortality. A persistent pattern of higher child mortality for females than for males is found, suggesting preferential care and treatment of male offspring. The higher mortality risk is found for infants born to very young and very old mothers, with short previous birth intervals, of higher birth orders, and where the previous infant had died. Among the socioeconomic characteristics, the education of the mother and rural-urban residence are found to affect infant survival. In childhood, among the demographic factors, only birth interval shows a significant effect on mortality. The risk of child mortality decreases considerably with the increase in the birth interval. The analysis of the effect of breastfeeding on mortality, although based on limited information, clearly shows the beneficial effect of breastfeeding on the infant's survival, especially during the early months of life. For all countries, the mortality rate for the non-breastfeeders is substantially higher than for the breastfeeders even when the effect of the other covariates is controlled.     

Housing quality and child mortality in the rural Philippines

Factors influencing child survival to age 5 are investigated for a rural sample in lloilo Province, Philippines. Considered are construction materials in walls, doors, windows, and floors and the typpes of toilet facilities. 707 women were asked how many children they had borne alive; the sexes and dates of each live birth; whether each child was still living; and if not at what age the child had died. This study focused retrospectively on mortality among 2359 children born between 1960 and 1973. About 4.9% had died before age 5. This is 1/2 of what was observed nationally for rural children in the 1978 fertility survey. Health conditions in rural Iloilo Province may have been more favorable than in other rural parts of the nation. Income generated from shipping, lumbering, and fish culture may have also contributed to the lower rate of child mortality observed in this sample. The sex ratio of the children was 102, well within the range regarded as typical. A logit regression was employed. Of the 207 girls with low demographic risk and worse quality housing, 249 were estimated to survive to age 5 and 18 to die before age 5. Sex was not an important factor in child mortality. Boys and girls had about equal chances of surviving. A social-demographic risk factor commonly linked with infant mortality is breast feeding. Breastfed infants from a number of developing countries have had lower rates of infant mortality. A slightly larger % of nonbreastfed children (96.9%) survived to age 5 than did breastfed children. Living in a poorly constructed dwelling reduced the odds of a child's survival. Estimates from the Brass method showed that the expected probability of children dying before age 5 was .073 and .035, representing life expectancies at birth of 63.4 and 69.9 years.     

Relationships between pregnancy spacing,sex of infants,maternal age,and birth order,and neonatal and post‐neonatal mortality in Bangladesh

Abstract

The relationships between length of the interpregnancy interval, outcome of the pregnancy preceding the interval, sex of the infants, pregnancy order, maternal age, and maternal history of previous child deaths and neonatal and postneonatal mortality were explored in a rural Bangladeshi population using a multiple regression analysis. Specific interactions between the interpregnancy interval, outcome of the pregnancy preceding the interval, sex of the infants, and history of previous child deaths were examined. An inverse relationship was observed between postneonatal mortality and the length of the interpregnancy interval when the pregnancy preceding the interval was a surviving infant. No such trend was observed for neonatal mortality. Post‐neonatal mortality rates among children whose mothers had experienced two or more previous child deaths were essentially the same as that for infants whose mothers had experienced 0–1 child deaths when the interpregnancy intervals were more than 24 months. Although female infants have a lower neonatal mortality than male infants, the neonatal mortality rate for female infants conceived less than twelve months following a male infant birth was higher than for a male infant conceived less than twelve months following another male infant birth. Post‐neonatal mortality is consistently higher for female compared to male infants in all interval categories.