A comparison of fertility control and lethal control of bovine tuberculosis in badgers: the impact of perturbation induced transmission.

In this paper we use mathematical modelling to consider the broad advantages and disadvantages of fertility control over lethal control for bovine tuberculosis in badger populations. We use a deliberately simple model, attempting to capture only the key transmission processes. The model is parametrized with reference to the long-term Woodchester Park study. Estimates of mortality rate from this study suggest no significant extra mortality risk for animals with evidence of infection as indicated by the presence of anti-Mycobacterium bovis antibodies or M. bovis isolation. We find that large reductions in prevalence are sometimes the consequence of only moderate reductions in population numbers. If we assume that the act of control does not in itself affect transmission rates, then as far as eradication is concerned, both fertility control and mortality control operate through the same epidemiological mechanism, the removal of susceptibles: if one is in principle capable of keeping a population low enough to be infection free then so is the other. It is necessary to continue either form of control at regular intervals to maintain a constant level of infection in the long term. If control were to be stopped, return to precontrol levels of badger population and infection prevalence would be expected within a few years. Fertility control is less effective in reducing population density than lethal control since it can only act, at maximum, to remove one age cohort per year. It is also less effective in reducing transmission as it can only ever remove susceptibles, while lethal control also removes infectious badgers. However, if the social disturbance caused by lethal control does in fact increase contact rates for the remaining infectious badgers, the relative efficacies of the two strategies become a great deal less clear. While we have no quantitative data on the extent to which social perturbation does act to promote transmission, model simulations show that it is possible to develop plausible scenarios in which the lethal control may actually act to increase the absolute numbers of animals infected, while reducing the number of uninfected animals to very low numbers.     

Protection afforded by sickle-cell trait (Hb AS): what happens when malarial selection pressures are alleviated?

A study of reproductive outcome in Mobile, AL was conducted among a large maternal cohort with sickle-cell disease (Hb SS), sickle-cell trait (Hb AS), and no hemoglobinopathies (Hb AA). It was found that mean gravidity and live births among Hb AS women were significantly higher than among Hb AA women. These findings were surprising since it is generally held that once malarial pressure is alleviated, any reproductive advantage that might be conferred by Hb AS would disappear and fertility levels would reach levels similar to or slightly less than that of Hb AA women. A search of the literature was subsequently conducted and a large cohort study of an African-derived population was found in the United Kingdom. Results from this study also showed that parity was significantly higher among Hb AS women compared to Hb AA women. If survivorship is similar among Hb AS and Hb SS women, findings from these two studies raise doubts whether directional selection is occurring against the Rb S allele in nonmalarial environments. Balancing selection may still be occurring.     

A regression approach to the projection of U.S. fertility based on past fertility data

The method of fertility projection used by the U.S. Bureau of the Census involves assumptions about the ultimate cohort total fertility rate and the ultimate cohort mean age at childbearing based on recent levels of fertility and women's birth expectations. This paper provides an outline of a general regression approach to fertility projection based on past data which would generate these two ultimate cohort characteristics. The technique is illustrated by using the U.S. single-year age-specific fertility rates up to 1986 for total women and projecting them indefinitely into the future until they become stable for both calendar years and cohorts.     

A regression approach to the projection of U.S. fertility based on past fertility data

Abstract

The method of fertility projection used by the U.S. Bureau of the Census involves assumptions about the ultimate cohort total fertility rate and the ultimate cohort mean age at childbearing based on recent levels of fertility and women's birth expectations. This paper provides an outline of a general regression approach to fertility projection based on past data which would generate these two ultimate cohort characteristics. The technique is illustrated by using the U.S. single‐year age‐specific fertility rates up to 1986 for total women and projecting them indefinitely into the future until they become stable for both calendar years and cohorts.     

Estimating parity of parents: application to the history of infertility among the !Kung of Southern Africa

We derive a method for interpreting information about the reproductive performance of mothers of a sample of informants and apply it to the history of low fertility among the !Kung of the Kalahari desert of southern Africa. The method formalizes the commonsense procedure of weighting mothers with 1 birth by 1, with 2 births by 1/2, with 3 births by 1/3, etc. An expression for the confidence interval of the estimate of mean completed fertility of fertile women in the mothers' cohort is given. Several independent studies show that !Kung women have low fertility, with a population average completed family size of slightly over 4. Our method, applied to the cohort of old informants, shows that fertility is comparable among !Kung women, mothers of old informants, who were born in the late nineteenth and early twentieth centuries. If the cause is an endemic infectious disease of long standing in this region, there are important implications for the history of southern and central Africa.     

Reducing Outbreaks: Using International Governmental Risk Pools to Fund Research and Development of Infectious Disease Medicines and Vaccines

The deadliest Ebola outbreak the world has ever seen is currently ravaging West Africa, despite the concerted efforts of the World Health Organization and many national governments. The current picture is troubling, but not altogether unexpected. Ebola was initially identified in 1976, and since that time, few drugs have been developed to combat it. The same is true for myriad other dangerous infectious diseases to which the world is currently susceptible. One proposal that might prevent outbreaks of this scale and magnitude from recurring would be to have the World Health Organization (WHO) and its technical partners assess which of its member states are at high risk for a disease, either directly or indirectly, and facilitate the creation of international governmental risk pools of those member states. Risk pools would offer open-indexed grant contracts to fund vaccine and drug development for a particular disease, and pharmaceutical companies could browse the index to apply for these grants. If the risk-pool states and a particular company sign a contract, a mutually agreed upon amount of the vaccine or drug would be produced at a below-market purchase price for those states. In return, the company would keep any patents or intellectual property rights for the developed vaccines or drugs. Risk-pool countries that did not use their vaccine or drug could resell that supply on secondary markets to other countries outside of the risk pool. This arrangement will increase the supply of tested drug and vaccine candidates available for combatting unexpected outbreaks of any previously discovered major infectious disease in the future.     

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.     

Condition, growth and reproduction in female red lechwe (Kobus leche leche Gray 1850)

Information on condition, growth and reproduction was collected from a sample of 155 female lechwe in the Linyanti Swamp, northern Botswana. Condition varied significantly with age, reproductive state and season and indications were found of relationships between body mass and the attainment of puberty in young females and body mass and the fertility of adult females. There were also indications that the population was under nutritional stress because of high water levels and that this had caused reductions in the growth rate and fertility of young females. It is suggested that the sensitivity of young females to adverse environmental conditions could be exploited to optimize population monitoring for conservation purposes by using them as an indicator class, rather than monitoring the entire population. Because of relationships between condition, growth and reproduction, it is also suggested that long-term monitoring of condition should form part of any effort to understand population dynamics.     

Does the anterior cruciate have a modeling threshold? A case for the affirmative

Growing evidence supports a 1972 proposal that dynamic tension strains of a ligament above a threshold range, but below its ultimate strength, would make its cells synthesize more collagen to thicken and strengthen it. If so, when that strengthening reduced later strains to the bottom of that threshold range this "diametric modeling" would stop. A) Such a mechanism must create a "strength-safety factor" that would minimize or prevent voluntary activities from rupturing healthy ligaments, so chiefly injuries would rupture them. B) Such a mechanism should also make the usual largest loads on a healthy anterior cruciate ligament (ACL) determine its strength, and would make smaller loads mixed with large ones have little effect on its strength. C) In principle, when an ACL's strains exceeded that threshold range, diametric modeling would turn on, strengthen it, and reduce subsequent strains from the same loads. When its strains remained smaller, this mechanically-controlled modeling would turn off. Normal ACLs do have a strength-safety factor so they could have a diametric modeling threshold too, as we now know bone does. In healthy young adult humans available evidence suggests that threshold's value could lie in the region of 23 Newtons/mmC of the ACL's cross section area. If similar relationships applied to fascia, tendons and other ligaments (I suggest they do), they would form fundamental biomechanical properties of collagenous tissue organs.     

A synthetic biosocial model of fertility transition: Testing the relative contribution of embodied capital theory,changing cultural norms,and women's labor force participation

This article presents a biosocial model of fertility decline, which integrates ecological‐economic and informational‐cultural hypotheses of fertility transition in a unified theoretical framework. The model is then applied to empirical data collected among 500 women from San Borja, Bolivia, a population undergoing fertility transition. Using a combination of event history analysis, multiple regression, and structural equation modeling, we examine the pathways by which education responds to birth cohort, parental education and network ties, and how age at first birth and total fertility, in turn, respond to birth cohort, social network ties, education, expectations about parental investment, work, and contraceptive use. We find that in addition to secular trends in education, respondent's education is associated with the education of parents, the investment she received from them, and the education of older siblings. Total fertility has dropped over time, partly in response to increased education; moreover, the behavior of other women in a woman's social network predicts both initiation of reproduction and total fertility, while expected parental investment in offspring negatively predicts total fertility. Involvement in paid work that is incompatible with childcare is associated with a later age of first reproduction, but not subsequent fertility. Contraceptive use partially mediates the effect of education and birth cohort on total fertility, but is not a mediator of the effect of social network or expected parental investment on total fertility. Overall, the empirical results provide support for a biosocial model of fertility decline, particularly the embodied capital and cultural pathways. Am J Phys Anthropol 154:322–333, 2014. © 2014 Wiley Periodicals, Inc.     

Continuing fertility transitions in a plural society: ethnic trends and differentials in Peninsular Malaysia

Fertility in Peninsular Malaysia has declined continuously from the late 1950s, reaching a total fertility rate of 3735 in 1983. All ethnic groups in Malaysia have contributed to this modern demographic transition but the rate of change has been most rapid for Chinese and Indians, Malay fertility having reached a plateau in the early 1980s. The effect of age structure, marital patterns and marital fertility (by parity) on the fertility declines for each ethnic community are analyzed. There has been a tendency, in each ethnic group, for the age distribution within the group of reproductive-age women to grow younger, reflecting the entry into the younger reproductive ages of the large birth cohorts of the 1950s and early 1960s. The effect of this on crude birth rates is hard to determine, because rising age at marriage and increasing use of contraception meant that fertility was increasingly concentrated in the more central reproductive ages. By the 1990s, the earlier declines in fertility will bring about a decline in the proportion of the total population made up of females in the main reproductive ages. After that point, further declines in fertility will be reflected in a sharper decline in the crude birth rate and hence the rate of population increase. Between 1947 and 1980, the age at marriage changed dramatically for females of all ethnic groups. The transition to higher age at marriage for Chinese was completed earlier, and since 1970 has risen by only a year. For Malays and Indians, the rise began later, proceeded faster and continued right up to 1980 when the medium ages at 1st marriage were Malays 22, Indians 23, Chinese 24 years. In 1980, Malay women on average were marrying 5 years later, and Indian women 6 years later than had their mothers' generation in 1947. The proportion never-married among Malay and Indian women aged 20-24 rose from 1/10 to 1/2 over this period; relatively greater changes are evident at ages 25-29. Other factors are the almost complete shift from parent-arranged to self-arranged marriages. Family size desired has decreased for all groups and the decline in breastfeeding has been offset by the sharp increase in the practice of contraception. Continuation of these trends would lead to replacement-level fertility for Malaysian Chinese and Indians by the year 2000. Malay fertility is likely to continue to decline but at a more moderate pace.     

Differential fertility in the United States, 1980: continuity or change?

This paper considers how changes in women's sociocultural characteristics have influenced recent patterns of differential fertility in the US and whether the convergence of fertility differentials observed up to 1970 has continued. The data are drawn from the June 1980 US Current Population Survey, which is a probability sample survey selected to represent the civilian non-institutionalized population living in households. The study population consists of 20,621 ever-married White and Black women aged 25-44, a group for various reasons considered to have a high impact from the point of view of fertility behavior. Fertility to date and ever expected fertility are the dependent variables. The respondents were separated into age cohorts, and differentiated by race. The data suggest that there has been no change in differential fertility in recent years: the 2 youngest cohorts (25-29 and 30-34 years) have similar expected fertilities that are lower than those of the older cohorts. Age at 1st birth, length of 1st birth interval, income, and education were negatively associated with fertility, among both older and younger women, of both races. Differentials by race have narrowed slightly. When fertility expectations were examined, the association of the independent variables with expected completed fertility was weaker among younger women, indicating that there has been some convergence in expected fertility. Further narrowing of differentials in actual fertility depends on how successful the younger women are in preventing future unplanned births. If the present tendency towards surgical sterilization (among both races and groups above and below the poverty level) persists, it will make it possible for more women to stay within their expected total fertility levels.     

Forecasting the obesity epidemic in the aging U.S. population

Objective: The objective was to forecast BMI distribution in the U.S. population along with demographic changes based on past race‐, sex‐, and birth cohort‐specific secular trends. Research Methods and Procedures: We compiled data from 44,184 subjects from 4 National Health and Nutrition Examination Surveys (NHANES; 1971 to 2004). By race and sex, we fit regression models to create smoothed mean BMI curves by age for 1970 to 2010. Linking corresponding birth cohorts across age‐ and year‐specific mean BMI projections, we estimated the trajectory of relative BMI throughout each cohort's lifetime. These projections were validated using actual cohorts in the Nurses’ Health Study and Health Professionals Follow‐up Study. Combined with U.S. census, we predicted BMI distributions in 2010 and examined the joint impact of the obesity epidemic and population aging. Results: BMI secular trends in the past 3 decades differ significantly by birth cohort, sex, and race. If these trends continue, the prevalence of obesity is expected to reach 35%, 36%, 33%, and 55% in 2010 among white men, white women, black men, and black women, respectively, far from the Healthy People 2010 goal of 15%. Such forecasts translate into 9.3 million more obese adults 20 to 74 years of age than in 2000, 8.3 million of whom would be 50 years of age or older, and 8.5 million of whom would be white. The mean age among obese men and women is also expected to rise from 47 to 49 years among whites and from 43 to 44 years among blacks. Discussion: As the baby boom generation approaches retirement age, the continuing obesity epidemic signals a likely expansion in the population with obesity‐related comorbidities. A framework to combine BMI and demographic trends is essential in evaluating the burden and disparity associated with the epidemic in the aging U.S. population.     

Population homeostasis in sub-Saharan Africa

Global population growth remains one of the major challenges of the twenty-first century. This is particularly true for African countries which have been undergoing their demographic transitions. To investigate whether predicted increasing population density and urbanization can help to stabilize African population, we construct a database for 84 georeferenced Demographic and Health Survey (DHS) samples including 947,191 individuals in sub-Saharan Africa and match each location with gridded population density from NASA. We apply a proportional hazard model to evaluate the quantitative impact of local population density on the transitions from childlessness to motherhood, and from celibacy to marriage. Moving from the 5th to the 95th percentile of population density increases the median age at first birth by 2.2 years. This roughly decreases completed fertility by half a child. The same increase in population density increases the median age at first marriage by 3.3 years. These findings contribute to the understanding of why fertility has not dropped in Africa as fast as expected. One part of the answer is that population density remains low. Yet the total effect of increased density on fertility remains limited and counting on it to stabilize the population would be unrealistic.     

Anticipation in bipolar affective disorder.

Anticipation refers to the increase in disease severity or decrease in age at onset in succeeding generations. This phenomenon, formerly ascribed to observation biases, correlates with the expansion of trinucleotide repeat sequences (TNRs) in some disorders. If present in bipolar affective disorder (BPAD), anticipation could provide clues to its genetic etiology. We compared age at onset and disease severity between two generations of 34 unilineal families ascertained for a genetic linkage study of BPAD. Life-table analyses showed a significant decrease in survival to first mania or depression from the first to the second generation (P < .001). Intergenerational pairwise comparisons showed both a significantly earlier age at onset (P < .001) and a significantly increased disease severity (P < .001) in the second generation. This difference was significant under each of four data-sampling schemes which excluded probands in the second generation. The second generation experienced onset 8.9-13.5 years earlier and illness 1.8-3.4 times more severe than did the first generation. In additional analyses, drug abuse, deaths of affected individuals prior to interview, decreased fertility, censoring of age at onset, and the cohort effect did not affect our results. We conclude that genetic anticipation occurs in this sample of unilineal BPAD families. These findings may implicate genes with expanding TNRs in the genetic etiology of BPAD.     

An Old Mom Keeps You Young: Mother’s Age at Last Birth and Offspring Longevity in Nineteenth-Century Utah

This study analyzes the intergenerational effects of late childbearing on offspring’s adult longevity in a population in Utah (United States) that does not display evidence of parity-specific birth control—a so-called natural fertility population. Studies have found that for women who experience late menopause and prolonged reproduction, aging is postponed and longevity is increased. This is believed to indicate female “robustness” and the impact of biological or genetic factors. If indeed there is a genetic component involved, one would expect to also find evidence for the intergenerational transmission of longevity benefits. Our study investigates the relationship between prolonged natural fertility of mothers and their offspring’s survival rates in adulthood. Gompertz regression models (N = 7,716) revealed that the offspring of mothers who were naturally fertile until a relatively advanced age lived significantly longer. This observed positive effect of late reproduction was not independent of but conditional upon survival of the mother to the end of her fecundity (defined as age 50). Offspring’s relative risks at death beyond age 50 were 6–12 percent lower than those of their counterparts born to mothers who had an average age at last birth. Our results, which account for various early, adult, and later-life conditions, as well as shared frailty, suggest that there is a positive relationship between mother’s age at last birth and offspring longevity, and strengthen the notion that age at menopause is a good predictor of this relationship.     

Fertility decline driven by poverty: the case of Addis Ababa, Ethiopia

Demographic transition theory states that fertility declines in response to development, thus wealth and fertility are negatively correlated. Evolutionary theory, however, suggests a positive relationship between wealth and fertility. Fertility transition as a result of industrialization and economic development started in the late 19th and early 20th centuries in Western Europe; and it extended to some of the Asian and Latin American countries later on. However, economic crises since the 1980s have been co-incident with fertility decline in sub-Sahara Africa and other developing countries like Thailand, Nepal and Bangladesh in the last decade of the 20th century. A very low level of fertility is observed in Addis Ababa (TFR=1.9) where contraceptive prevalence rate is modest and recurrent famine as well as drought have been major causes of economic crisis in the country for more than three consecutive decades, which is surprising given the high rural fertility. Detailed socioeconomic and demographic characteristics of 2976 women of reproductive age (i.e. 15-49 years) residing in Addis Ababa were collected during the first quarter of 2003 using an event history calendar and individual women questionnaire. Controlling for the confounding effects of maternal birth cohort, education, marital status and accessible income level, the poor (those who have access to less than a dollar per day or 250 birr a month) were observed to elongate the timing of having first and second births, while relatively better-off women were found to have shorter birth intervals. Results were also the same among the ever-married women only model. More than 50% of women currently in their 20s are also predicted to fail to reproduce as most of the unmarried men and women are 'retreating from marriage' due to economic stress. Qualitative information collected through focus group discussions and in-depth interviews also supports the statistical findings that poverty is at the root of this collapse in fertility. Whilst across countries wealth and fertility have been negatively correlated, this study shows that within one uniform population the relationship is clearly positive.     

Twenty years' demographic change in sedentes and migrants of an international migrant-sending community in Tonga

In the Kingdom of Tonga, migration to overseas developed countries has prevailed. To elucidate the effects of migration on population dynamics, an interview survey was conducted in the migrant-sending community of Kolovai, in the outer region of Tongatapu Island. All births, deaths, marriages and in- and out-migrations that took place between 1983 and 2002 were recorded for all members of the 'Kolovai population', consisting of persons who had lived in this community for at least a one-year period during this 20 years. The 'Kolovai population' members, numbering 1184 (564 males and 620 females), were divided into three groups based on residence at the end of each year, i.e. Kolovai (called KK), other places in Tonga (KT) or overseas countries (KO). The KK population decreased from 774 in 1982 to 570 in 2002, owing mostly to an increase of 167 persons as the natural balance and a decrease of 324 persons as the balance of international migration. Comparison of total fertility rate (TFR) between KK and KO women revealed that the mean TFR of the former decreased from 3.460 in the earlier 10-year period (1983-1992) to 2.240 in the later 10-year period (1993-2002), while that of the latter was more than 3.5 in both 10-year periods. This difference was largely due to the decrease in the proportion married among KK women. If the current trends of international migration and fertility continue, the population of Kolovai will be reduced and its age composition will become cylinder-shaped in the near future.     

Number and sex ratio of children and impact of parental diabetes in individuals with Type 1 diabetes

Diabet. Med. 29, 1268-1271 (2012) ABSTRACT: Objective To assess the number and sex ratio of children in individuals with Type?1 diabetes mellitus and the influence of parental diabetes on age at onset of Type?1 diabetes in our cohort. Methods In a cross-sectional study in a German region comprising 350?000 inhabitants, 697 subjects with Type?1 diabetes (364 women, 333 men) underwent a standardized assessment regarding the number and sex of their children and the family history of diabetes. Results Compared with 1.36 children per woman in the German background population, the total fertility rate in the calendar year of 2010 in our female cohort with Type?1 diabetes (age 18-49?years) was 0.88. Men with Type?1 diabetes had a fertility rate of 0.65. More men (51.1%) than women (35.7%; P?相似文献