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.     

Population based study of rates of multiple pregnancies in Denmark, 1980-94.

OBJECTIVE: To study trends in multiple pregnancies not explained by changes in maternal age and parity patterns. DESIGN: Trends in population based figures for multiple pregnancies in Denmark studied from complete national records on parity history and vital status. POPULATION: 497,979 Danish women and 803,019 pregnancies, 1980-94. MAIN OUTCOME MEASURES: National rates of multiple pregnancies, infant mortality, and stillbirths controlled for maternal age and parity. Special emphasis on primiparous women > or = 30 years of age, who are most likely to undergo fertility treatment. RESULTS: The national incidence of multiple pregnancies increased 1.7-fold during 1980-94, the increase primarily in 1989-94 and almost exclusively in primiparous women aged > or = 30 years, for whom the adjusted population based twinning rate increased 2.7-fold and the triplet rate 9.1-fold. During 1989-94, the adjusted yearly increase in multiple pregnancies for these women was 19% (95% confidence interval 16% to 21%) and in dizygotic twin pregnancies 25% (21% to 28%). The proportion of multiple births among infant deaths in primiparous women > or = 30 years increased from 11.5% to 26.9% during the study period. The total infant mortality, however, did not increase for these women because of a simultaneous significant decrease in infant mortality among singletons. CONCLUSIONS: A relatively small group of women has drastically changed the overall national rates of multiple pregnancies. The introduction of new treatments to enhance fertility has probably caused these changes and has also affected the otherwise decreasing trend in infant mortality. Consequently, the resources, both economical and otherwise, associated with these treatments go well beyond those invested in specific fertility enhancing treatments.     

Socioeconomic status and infant mortality among Hispanics in a southwestern city

Recent investigations of infant mortality in the Southwest part of the US have shown that Spanish surname infant death rates are lower than might be expected from the relatively low socioeconomic standing of the Spanish surname population, a phenomenon that appears to be confined to the neonatal componont of the infant mortality rate. The relationship between socioeconomic status (ses) and infant mortality is examined overall and separately within the Anglo and Spanish surname populations of Corpus Christ, Texas. The investigation utilizes data from the 36 Nueces County census tracts. Most recent data on infant, neonatal, and postneonatal mortality was provided by the local health department. Subjects were limited to Anglos and those whites with at least 1 Spanish surname parent. The 1979-1983 cohort is analyzed. Information from the 1980 US census was utilized to divide the 36 census tracts into 3 SES groups: high, medium and low. The most immediately striking aspect of the findings is the significant inverse gradient in Anglos between SES and both the total infant mortality rate (IMR) and the neonatal mortality (NMR), a gradient which is nonexistent in the Spanish surname population as well as overall. In addition, Anglos and Spanish persons differ significantly with respect to all IMRs and NMRs. In the high and medium SES groups and overall, all Anglo rates are lower, while in the low SES group, Spanish surname rates are lower. These findings suggest that, among Anglos, SES is a crucial factor in infant deaths, whereas, among the Spanish surname population, having a medium or high SES does not offer any additional protection against mortality. Alternatively, lower SES does not translate into significantly lower infant mortality among Spanish persons. These findings provide support for the study's hypotheses that the SES-infant mortality association is weaker among Spanish persons than among Anglos. The analysis also shows the importance of analyzing the SES-infant mortality association separately by ethnicity. Studies in larger cities and also studies utilizing matched birth and death records are needed to further elaborate these findings.     

Breast-feeding pattern in an urban Nigerian community

This paper examines the pattern of breastfeeding among women still in their prime childbearing ages (15-35 years) in Ilorin, the capital city of Kwara state in Nigeria. While breastfeeding is still a common practice among urban women, there is wide variation in the duration of breastfeeding depending on the socioeconomic characteristics of the mothers. Mother's education and father's education have very strong negative associations with duration of breastfeeding. Use of contraception also has a significant independent but negative effect on breastfeeding duration. Christians continue breastfeeding for shorter periods than Muslims. The introduction of supplementary feedings to the infant occurs in this population much earlier than is recommended by various authorities. Decline in breastfeeding practice may have deleterious effects on the health and survival of children in developing countries and may also lead to higher fertility and more rapid population growth. The high morbidity and mortality among artificially fed infants in many developing countries can be attributed to improper preparation as well as contamination of infant formula and other foods.     

Perinatal mortality and adverse pregnancy outcomes in a low-income rural population of women who smoke

We describe adverse pregnancy outcomes, including congenital anomalies, fetal, neonatal, and infant mortality among a Missouri population of low-income, rural mothers who participated in two randomized smoking cessation trials. In the Baby BEEP (BB) trial, 695 rural women were recruited from 21 WIC clinics with 650 women's pregnancy outcomes known (93.5% retention rate). Following the BB trial, 298 women who had a live infant after November 2004 were recruited again into and completed the Baby Beep for Kids (BBK) trial. Simple statistics describing the population and perinatal and postneonatal mortality rates were calculated. Of the adverse pregnancy outcomes (n = 79), 29% were spontaneous abortions of less than 20 weeks' gestation, 23% were premature births, and 49% were identified birth defects. The perinatal mortality rate was 15.9 per 1000 births (BB study) compared with 8.6 per 1000 births (state of Missouri) and 8.5 per 1000 births (United States). The postneonatal infant mortality rate was 13.4 per 1000 live births (BBK) compared with 2.1 per 1000 live births (United States). The health disparity in this population of impoverished, rural, pregnant women who smoke, particularly in regard to perinatal and infant deaths, warrants attention.     

Causes and consequences of increase in child survival rates: ethnoepidemiology among the Hmong of Thailand.

The Hmong "hill tribe" minority in Thailand has much higher exposure to factors usually associated with risk of child mortality (high fertility, low status of women, low education, less use of modern medical care for births, exposure to warfare, economic and physical disruption, and poor hygienic conditions) than the rural ethnic Thai population. Nonetheless, infant mortality has declined from over 120 per 1000 to under 50 per 1000 live births among both these populations in the past 30 years. The reason for the rapid increase in child survival among the Hmong appears to be better access to and more use of modern curative and preventive medical care associated with road construction rather than major changes in social or hygienic conditions. Conventional wisdom suggests that high fertility is both a cause and a consequence of high infant and child mortality and that parents will not reduce fertility until they see that mortality has declined. Most Hmong parents recognize the decline in child mortality and attribute it to better access to modern medical care. Most Hmong parents also say that, if they were starting to have children now, they would want to have fewer children. Fear of child death is infrequently mentioned as a motive for having more children, and the perceived decline in child mortality is rarely mentioned as a reason for reduced fertility. Most Hmong parents explain their desired family size in terms of economic conditions rather than perceived risk of child mortality. Results of this study suggest that fertility and child mortality can vary independently of one another and that major reductions in child mortality can be accomplished without waiting for major social changes (e.g., improved education or status of women) or major reductions in fertility.     

Perinatal mortality and adverse pregnancy outcomes in a low‐income rural population of women who smoke

We describe adverse pregnancy outcomes, including congenital anomalies, fetal, neonatal, and infant mortality among a Missouri population of low‐income, rural mothers who participated in two randomized smoking cessation trials. In the Baby BEEP (BB) trial, 695 rural women were recruited from 21 WIC clinics with 650 women's pregnancy outcomes known (93.5% retention rate). Following the BB trial, 298 women who had a live infant after November 2004 were recruited again into and completed the Baby Beep for Kids (BBK) trial. Simple statistics describing the population and perinatal and postneonatal mortality rates were calculated. Of the adverse pregnancy outcomes (n = 79), 29% were spontaneous abortions of less than 20 weeks' gestation, 23% were premature births, and 49% were identified birth defects. The perinatal mortality rate was 15.9 per 1000 births (BB study) compared with 8.6 per 1000 births (state of Missouri) and 8.5 per 1000 births (United States). The postneonatal infant mortality rate was 13.4 per 1000 live births (BBK) compared with 2.1 per 1000 live births (United States). The health disparity in this population of impoverished, rural, pregnant women who smoke, particularly in regard to perinatal and infant deaths, warrants attention. Birth Defects Research (Part A), 2012. © 2012 Wiley Periodicals, Inc.     

Demographic and health patterns in a rural community from the Basque area in Spain (1800-1990)

In this work, the evolution of demographic and health patterns in a Basque rural population from Spain is analysed, as they relate to progress in demographic and epidemiological transition. For this purpose, parochial record data on 13,298 births and 9,215 deaths, registered during the 19th and 20th centuries (1800-1990), were examined. The study area is a rural community called Lanciego, which is located at the southern end of the Rioja Alavesa area (Alava Province, Basque Country). In Lanciego, demographic transition began in the final decade of the 19th century, when a definite, irreversible trend began towards a reduction in mortality. The decrease in the birth rate came later than that in the death rate, and did not start until the 1930s. The post-transitional stage seemed to be reached in the 1970s, when the birth and death rates showed values below 20 per 1,000. Other characteristics observed for the post-transitional stage in Lanciego are: (i) very low rates of infant mortality achieved at the expense of effective control of exogenous mortality; (ii) the mortality curve by ages changes from a U-shape (typical of populations with a high infant mortality rate and low life expectancy at birth) to a J-shape more characteristic of modern societies where longevity and life expectancy are considerably higher; (iii) a certain level of over-mortality among women in the senior age group (>65); and (iv) a significant proportion of mortality in recent times (1970-90) resulting from cardiovascular diseases and malignant neoplasms (post-transition causes). This last point is in contrast with observations from the first four decades of the 20th century, when infectious diseases and respiratory ailments were determining factors in mortality among this population. The data provided by the study of the variation over time in demographic and health patterns indicate that reducing the risk of mortality is one of the most important preconditions for fertility decline.     

Estimating infant mortality rates prospectively in Honduras.

In order to determine the validity of infant mortality estimates based on retrospective reporting, the Honduran Ministry of Health carried out a follow-up survey of women interviewed in a 1987 national survey. Women were interviewed approximately 14 months after the baseline survey and were asked about the outcomes of their pregnancies and the survival status of their young children. The overall infant mortality rate calculated from the follow-up survey was lower than that obtained from the baseline survey, due to the particularly low rate among the group of women who were pregnant at the time of the baseline survey. Possible explanations for this low rate are discussed.     

The delineation of fertility strategies in a tribal population of India: the Koyas of Koraput District,Orissa

Demographic data collected for a tribal population of India, the Koyas of Koraput District, Orissa, were examined in light of 2 models of reproductive behavior associated with the economic value of children: the replacement effect and son survivorship motivation. Both models are united in the concept that infant/child mortality affects subsequent fertility. The database consists of retrospective fertility histories of Koya women who had completed their reproductive period. The total number was 260, with the total offspring numbering 1407. 2 distinct cohorts of women were formed for the purpose of analysis, separated only by the criterion of offspring survival: women who had experienced infant child mortality (129 women with 739 children); and women who completed their reproductive period without suffering offspring loss of this nature (132 women with 668 children). The cohort without child loss had a mean parity of 5.10, lower than the average parity of 5.73 recorded for the cohort whose reproductive histories included at least 1 infant/child death. Age specific marital fertility and birth interval analyses indicated that this differential was because of biological, not behavioral, factors. The age pattern of fertility of females suffering offspring mortality failed to demonstrate a high rate of childbearing in the later age intervals of the reproductive period, a characteristic pattern of couples attempting to "replace" lost offspring. Birth interval analysis pointed to biological "interval effect," whereby infant/child mortality caused a cessation of lactation and hence a shortening of postpartum amenorrhea. Computer simulation further indicated that the higher fertility differential of the cohort experiencing offspring loss still did not result in high son survivorship values. The findings agree with earlier studies indicating that for predemographic transitional populations, economically motivated fertility strategies are ineffectual.     

Excess Mortality in Patients with Severe Mental Disorders in 1996-2010 in Finland

Unselected population-based nationwide studies on the excess mortality of individuals with severe mental disorders are scarce with regard to several important causes of death. Using comprehensive register data, we set out to examine excess mortality and its trends among patients with severe mental disorders compared to the total population. Patients aged 25–74 and hospitalised with severe mental disorders in 1990–2010 in Finland were identified using the national hospital discharge register and linked individually to population register data on mortality and demographics. We studied mortality in the period 1996–2010 among patients with psychotic disorders, psychoactive substance use disorders, and mood disorders by several causes of death. In addition to all-cause mortality, we examined mortality amenable to health care interventions, ischaemic heart disease mortality, disease mortality, and alcohol-related mortality. Patients with severe mental disorders had a clearly higher mortality rate than the total population throughout the study period regardless of cause of death, with the exception of alcohol-related mortality among male patients with psychotic disorders without comorbidity with substance use disorders. The all-cause mortality rate ratio of patients with psychotic disorders compared to the total population was 3.48 (95% confidence interval 2.98–4.06) among men and 3.75 (95% CI 3.08–4.55) among women in the period 2008–10. The corresponding rate ratio of patients with psychoactive substance use disorders was 5.33 (95% CI 4.87–5.82) among men and 7.54 (95% CI 6.30–9.03) among women. Overall, the mortality of the total population and patients with severe mental disorders decreased between 1996 and 2010. However, the mortality rate ratio of patients with psychotic disorders and patients with psychoactive substance use disorders compared to the total population increased in general during the study period. Exceptions were alcohol-related mortality among patients with psychoactive substance use disorders and female patients with psychotic disorders, as well as amenable mortality among male patients with psychotic disorders. The mortality rate ratio of persons with mood disorders compared to the total population decreased. The markedly high mortality amenable to health care intervention among patients with severe mental disorders found in our study suggests indirectly that they may receive poorer quality somatic care. The results highlight the challenges in co-ordinating mental and somatic health services.     

Population Control in Confined Colonies of Golden Hamsters (Mesocricetus auratus Waterhouse)

The mechanisms by which confined colonies of Golden Hamsters regulate the density of their population were investigated. Six experimental populations were established with two ♂♂ and two ♀♀ each and allowed to grow freely for 3–8 months. At no time did any population exceed eight individuals. This appeared to be the result of a high rate of infant mortality due to failure of pregnant and parturient ♀♀ to isolate themselves from the others. Two other populations were then established allowing many more nesting areas and more room for dispersal, but animals continued to crowd together and infant survival did not improve. These results contrast sharply with the large ultimate populations and only slowly developing disturbances seen in rats and mice. This difference in population control appears to be the direct result of a species difference in the tolerance of adults for strange newborns. In two further short-term experiments, the effects of the number and sex of adults in the founding population were systematically examined. The critical density at which no pups survived past the first day was six or more animals; ♀♀ appeared to contribute more than ♂♂ to infant mortality.     

Bevölkerungswachstum: Bildung ist die Lösung

Population growth – education is the answer Over the last decades world population has been constantly growing by some 80 million per year. Whereas the growth rate as well as the fertility rate have been cut by half since the 1970th, population growth will continue well over mid‐century. As the developed countries have completed the demographic transition from high mortality and fertility rates to low ones, population growth is fading out there or has already been reversed into decline. In the least developed countries mortality has fallen as well, whereas fertility decline has stalled. Therefor population growth is very high making the solution of the widespread problems in this part of the world more and more difficult. One obvious way out of this trap would be a better education that could open new development perspectives. A positive side effect is that educated women have much less offspring than their counterparts who never went to school.     

Maternal Investment and Infant Survival in Gray-Cheeked Mangabeys (Lophocebus albigena)

Differences among females in infant survival can contribute substantially to variance in fitness. Infant survival is a product of external risk factors and investment by kin, especially the mother, and is thus closely tied with the evolution of behavior and life history. Here we present a 9-yr study (2004–2012) of infant survival and sex ratio relative to age and dominance ranks of mothers and the presence of immigrant males in a free-ranging population of gray-cheeked mangabeys (Lophocebus albigena) in Kibale National Park, Uganda. We consider immigrant males because they are known to increase infant mortality in several other species. We found that infants of older mothers had higher survival than those of younger mothers but that high rank did not confer a significant benefit on infant survival. Female infants had higher survival than male infants. Young, low-ranking females had more male infants than young, high-ranking females, which had slightly more daughters, but this difference declined as females aged because low-ranking females had more daughters as they aged. With limited data, we found a significant relationship between the presence of male immigrants and infant mortality (falls and unexplained disappearances) to 18 mo. Our results suggest that infant survival in gray-cheeked mangabeys is most precarious when mothers must allocate energy to their own growth as well as to their infants, that sons of young mothers are at greatest risk, and that immigrant males can negatively affect infant survival.     

Consanguinity, fertility of couples and mortality of children in the high Atlas population (commons of Anougal and Azgour, Marrakesh, Morroco)

This study analyses the relationship between consanguinity, fertility and child mortality in a rural population of two moroccan High-Atlas valleys. Among this very endogamous population, we have reconstituted, by inquiries, for each family, the totality of its reproductive life as well as the genealogic relationships that exist between the spouses on several generations. The analysis carried out on the group of families with women who are over 40 years old (438 families) has shown that the population was very strong related (28% of marriages are consanguineaous). A positive association between levels of fertility, infant mortality and consanguinity was observed.     

Biosocial covariates of adult male body mass index in Central India

Body mass index (BMI) is the 'measuring rod' of nutritional status. This study investigates the type and extent of correlation between adult male BMI and socioeconomic, cultural and bio-demographical variables using data from 11,496 individuals from 38 districts of Central India. For each individual, stature, body weight and sitting height data were collected, their Cormic index and BMI computed, and averages for each district calculated. Mean BMI was found to be lowest for the population of Tikamgarh (17.90+/-1.91 kg m(-2)) and highest for that of Durg district (19.33+/-2.16 kg m(-2)), whereas the mean BMI for the total population of Central India was 18.67+/-2.18 kg m(-2), which is lower than that of well-to-do individuals in India as a whole. The F ratio indicates that there is inter-district variation in anthropometric characteristics of populations. District-wise biosocial indicators were obtained, namely population density per square kilometre, percentage urban population, percentage of population that is of scheduled caste/tribe, sex ratio, average rural population per PHC/CHC (primary or community health centre), literacy rate, life expectancy, total fertility rate, infant mortality rate, gender development index and human development index. Most of these variables were found to be significantly correlated with each other, but BMI was only significantly correlated with three of them, viz. gender development index (R2=0.211), life expectancy (R2=0.130) and infant mortality rate (R2=0.128). Gender development index and life expectancy were positively correlated with BMI, whereas infant mortality rate was negatively correlated. It is concluded that if BMI increases then life expectancy will also increase. Thus better nutritional status may be a helpful tool for reducing infant mortality rate, which is an indicator of socioeconomic status, health condition, health care and ultimately overall development of a region or population.     

Unemployment and mortality in Denmark, 1970-80.

Relative mortality in the period 1970-80 was studied among Danish men and women who were unemployed and employed on the day of the 1970 census. The study population consisted of the total labour force in the age range 20-64 on 9 November 1970--that is, about 2 million employed and 22,000 unemployed people. Relative mortality was analysed by a multiplicative hazard regression model (as a natural extension of the standardised mortality ratio) and a multiplicative regression model with extra-Poisson variation. A significantly increased death rate (40-50%) was found among the unemployed after adjusting for occupation, housing category, geographical region, and marital state. Analysis of five main causes of death showed increased mortality from all causes, but especially from suicide or accidents. In areas where the local unemployment rate was comparatively high the relative mortality among the unemployed was lower. The increased mortality among the unemployed was interpreted as a consequence of health related selection as well as increased susceptibility associated with the psychosocial stress of unemployment.     

An evolutionary model of stature, age at first birth and reproductive success in Gambian women

We have built a model to predict optimal age at first birth for women in a natural fertility population. The only existing fully evolutionary model, based on Ache hunter-gatherers, argues that as women gain weight, their fertility (rate of giving birth) increases-thus age at first birth represents a trade-off between time allocated to weight gain and greater fertility when mature. We identify the life-history implications of female age at first birth in a Gambian population, using uniquely detailed longitudinal data collected from 1950 to date. We use height rather than weight as an indicator of growth as it is more strongly correlated with age at first birth. Stature does not greatly influence fertility in this population but has a significant effect on offspring mortality. We model age at first reproduction as a trade-off between the time spent growing and reduced infant mortality after maturation. Parameters derived from this population are fitted to show that the predicted optimal mean age of first birth, which maximizes reproductive success, is 18 years, very close to that observed. The reaction norm associated with variation in growth rate during childhood also satisfactorily predicts the variation in age at first birth.     

Optimal birthweights in Peruvian populations at high and low altitudes

This study tests the hypothesis that optimum birthweight for survival is lower among hospital-born infants in Puno, Peru (altitude 3860 m) than that among their counterparts at low altitude in Tacna, Peru (altitude 600 m). The data are derived from hospital birth records for 1971 and 1972 and municipal death records for 1971 through 1973. Linking these records permits analysis of the patterns of mortality in relation to birthweight. Stabilizing selection upon birthweight is operating in both populations. The high altitude population has a lower mean birthweight and a lower optimal birthweight. The Puno population is closer to its optimal birthweight distribution and, as a result of mortality during infancy, is approaching its optimum birthweight distribution for survival more rapidly than the Tacna population. It appears that the high altitude Puno population may well be adapted to its environment in the sense that there is less selective mortality on birthweight phenotypes.     

Natural selection among Kinnaura of the Himalayan highland: A comparative analysis with other Indian and Himalayan populations

The present investigation on fertility and mortality differential among Kinnaura of the Himalayan highland is based on data collected from 160 post-menopausal women belonging to the middle and high altitude region of Kinnaur district of Himachal Pradesh (Indian Himalayas). Selection potential based on differential fertility and mortality was computed for middle-and high-altitude women. Irrespective of the methodology, the total index of selection was found to be highest among middle-altitude women (0.386) as compared with high-altitude (0.370) women, whereas for the total population it is estimated to be 0.384. It was found that the Kinnaura of the Himalayan highland showing moderate index of total selection and relative contribution of the mortality component (Im) to the index of total selection is higher than the corresponding fertility component (If). The analysis of embryonic and post-natal mortality components shows that the post-natal mortality components are higher in comparison with the embryonic mortality components among highlanders and needs special intervention and health care. The present findings are compared with other Indian tribes as well as non-tribes of the Himalayan region and other parts of the country. It reveals that this index among Kinnaura is moderate than the other population groups; among the Himalayan population, the highest was reported for Galong (It = 1.07) of Arunachal, whereas the lowest was reported from Ahom (It = 0.218) of Manipur. The correlation and regression analysis between total index of selection (It) and fertility (If) and mortality (Im) components for pooled data of populations of the Indian Himalayan states show that If and Im account for 21.6 and 29.1% variability, respectively. In Crow's total index of selection (It) along with strong association, which is significant at the 1% level, this indicates that mortality plays a greater role in natural selection in comparison with fertility among populations of the Indian Himalayas.