A dynamic model of the marriage market-Part 2: simulation of marital states and application to empirical data.

A dynamic, two-sex, age-structured marriage model is presented. Part 1 focused on first marriage only and described a marriage market matching algorithm. In Part 2 the model is extended to include divorce, widowing, and remarriage. The model produces a self-consistent set of marital states distributed by age and sex in a stable population by means of a gender-symmetric numerical method. The model is compared with empirical data for the case of Zambia. Furthermore, a dynamic marriage function for a changing population is demonstrated in simulations of three hypothetical scenarios of elevated mortality in young to middle adulthood. The marriage model has its primary application to simulation of HIV-AIDS epidemics in African countries.

A dynamic model of the marriage market-part 1: matching algorithm based on age preference and availability.

The matching algorithm in a dynamic marriage market model is described in this first of two companion papers. Iterative Proportional Fitting is used to find a marriage function (an age distribution of new marriages for both sexes), in a stable reference population, that is consistent with the one-sex age distributions of new marriages, and includes age preference. The one-sex age distributions (which are the marginals of the two-sex distribution) are based on the Picrate model, and age preference on a normal distribution, both of which may be adjusted by choice of parameter values. For a population that is perturbed from the reference state, the total number of new marriages is found as the harmonic mean of target totals for men and women obtained by applying reference population marriage rates to the perturbed population. The marriage function uses the age preference function, assumed to be the same for the reference and the perturbed populations, to distribute the total number of new marriages. The marriage function also has an availability factor that varies as the population changes with time, where availability depends on the supply of unmarried men and women. To simplify exposition, only first marriage is treated, and the algorithm is illustrated by application to Zambia. In the second paper, remarriage and dissolution are included.

HCV burden of infection in Egypt: results from a nationwide survey.

Egypt is the country with the largest hepatitis C virus (HCV) epidemic in the world. In 2008, a Demographic Health Survey (DHS) was carried out in Egypt, providing for the first time a unique opportunity for HCV antibody testing on a nationwide representative sample of individuals. Consenting individuals answered a questionnaire on socio-demographic characteristics and iatrogenic exposures, before providing a blood sample for HCV antibody testing by enzyme-linked immunosorbent assay. Factors independently associated with HCV infection were examined through multivariate logistic regression models. Of 12 780 eligible subjects aged 15-59 years, 11 126 (87.1%) agreed to participate and provided a blood sample. HCV antibody prevalence nationwide was 14.7% (95% CI 13.9-15.5%) in this age group. HCV antibody prevalence gradually increased with age, reaching, in the 50-59 years age group, 46.3% and 30.8% in males and females, respectively. It was higher in males compared to females (17.4% versus 12.2%, respectively, P < 0.001), and in rural compared to urban areas (18.3% versus 10.3%, respectively, P < 0.001). In multivariate analysis, age, male sex, poverty, past history of intravenous anti-schistosomiasis treatment, blood transfusion, and living outside of the Frontier Governorates were all significantly associated with an increased risk of HCV infection. In addition, in urban areas, lack of education and being circumcised for females were associated with an increased risk of HCV infection. This study confirmed on a nationwide representative sample the very high HCV antibody prevalence in Egypt. It stresses the urgent need for strengthening prevention efforts, and bringing down the costs of antiviral drugs for countries like Egypt, where the people in the most precarious situations are also those most likely to be infected by the virus.

Commercial sex and HIV transmission in mature epidemics: a study of five African countries.

The study compares the association between using the services of commercial sex workers and male HIV seroprevalence in five African countries: Ghana, Kenya, Lesotho, Malawi and Rwanda. The HIV seroprevalence among men who 'ever paid for sex' was compared with controls who 'never paid for sex'. Results were based on 12,929 eligible men, aged 15-59 years, interviewed in Demographic and Health Surveys. The odds ratio of HIV seroprevalence associated with ever paying for sex was 1.89 (95% confidence interval = 1.57-2.28), with only minor differences by country. The results were stable in multivariate analysis after controlling for available potential cofactors (data on non-sexual routes of transmission were not available). Given the relatively small proportion of men involved, the risk attributable to 'ever paying for sex' remained low: 7.1% in univariate analysis and 4.4% after adjustment, and it varied among countries (range 1.3-9.4%). These results match previous observations that commercial sex seems to play a minor role in the spread of HIV in mature epidemics.

Access to medicines in Senegal: results of a sample survey.

The survey was conducted in Senegal in April 2001 on a representative sample of providers and clients. Results show that access to medicines in Senegal was limited for three main reasons: (1) the supply of drugs was inadequate, and even critical drugs were often missing in health centres, and were somewhat less in pharmacies; (2) the health infrastructures appeared insufficient to cover the needs of the whole population, creating high opportunity costs; (3) the cost of the drugs prescribed was higher than the minimum price, sometimes exceeding the capacity of poorer people, although high cost was seldom reported as the main reason for not acquiring prescribed drugs. Improving access to medicine is a priority to help reduce health inequalities in developing countries.

Fertility Trend and Pattern in a Rural Area of South Africa in the Context of HIV/AIDS

Little is known about the dynamics of fertility transition in South Africa; though recent studies have begun to shed light on demographic changes in the country. This study presents trends and patterns of fertility observed in a rural South African population. Various demographic and statistical techniques were used to examine fertility patterns in a population of 21;847 women in a rural KwaZulu-Natal (KZN) demographic surveillance area. These are compared with patterns seen in another South African rural population under demographic surveillance; and with data from the 1998 South Africa Demographic and Health Survey. Findings are interpreted in light of contraceptive use patterns and HIV prevalence in the population. In South Africa; the end of the fertility transition is now in sight. In rural KZN; where national fertility levels are highest; fertility has declined rapidly for about two decades and would have reached below replacement level in 2003. While fertility has declined rapidly among all women over age 18 years; fertility levels among adolescents have not changed in decades. Although most adolescents in rural KZN were sexually active (60 ); few had ever used contraception (20 ). High HIV seroprevalence appears to explain a small part of the fertility decline (12 ); however; this effect is likely to grow in the near future as the HIV/AIDS epidemic continues in South Africa. If the current trends continue in the future; below replacement fertility; together with high mortality due to AIDS; it could soon lead to negative natural population growth in rural South Africa

Effect of zinc supplementation on growth in West African children: a randomized double-blind placebo-controlled trial in rural Burkina Faso.

OBJECTIVE: To analyse the effects of zinc supplementation on growth parameters in a representative sample of young children in rural Burkina Faso. Design Randomized, double-blind, placebo-controlled efficacy trial. Setting Eighteen villages in rural northwestern Burkina Faso. Subjects In all, 709 children aged 6-31 months were enrolled; 685 completed the trial. Intervention Supplementation with zinc (12.5 mg zinc sulphate) or placebo daily for 6 days a week for 6 months. Outcomes Weight, length/height, mid-arm circumference, and serum zinc. RESULTS: In a representative subsample of study children, 72% were zinc-deficient at baseline. After supplementation, serum zinc increased in zinc-supplemented but not in control children of the subsample. No significant differences between groups were observed during follow-up regarding length/height, weight, mid-arm circumference, and z scores for height-for-age, weight-for-age, and weight-for-height. CONCLUSIONS: We conclude that zinc supplementation does not have an effect of public health importance on growth in West African populations of young children with a high prevalence of malnutrition. Multinutrient interventions are likely to be more effective.

Effect of zinc supplementation on malaria and other causes of morbidity in west African children: randomised double blind placebo controlled trial.

OBJECTIVE: To study the effects of zinc supplementation on malaria and other causes of morbidity in young children living in an area holoendemic for malaria in west Africa. DESIGN: Randomised, double blind, placebo controlled efficacy trial. SETTING: 18 villages in rural northwestern Burkina Faso. PARTICIPANTS: 709 children were enrolled; 685 completed the trial. INTERVENTION: Supplementation with zinc (12.5 mg zinc sulphate) or placebo daily for six days a week for six months. MAIN OUTCOME MEASURES: The primary outcome was the incidence of symptomatic falciparum malaria. Secondary outcomes were the severity of malaria episodes, prevalence of malaria parasite, mean parasite densities, mean packed cell volume, prevalence of other morbidity, and all cause mortality. RESULTS: The mean number of malaria episodes per child (defined as a temperature >/=37.5 degrees C with >/=5000 parasites/microliter) was 1.7, 99.7% due to infection with Plasmodium falciparum. No difference was found between the zinc and placebo groups in the incidence of falciparum malaria (relative risk 0.98, 95% confidence interval 0.86 to 1.11), mean temperature, and mean parasite densities during malaria episodes, nor in malaria parasite rates, mean parasite densities, and mean packed cell volume during cross sectional surveys. Zinc supplementation was significantly associated with a reduced prevalence of diarrhoea (0.87, 0.79 to 0.95). All cause mortality was non-significantly lower in children given zinc compared with those given placebo (5 v 12, P=0.1). CONCLUSIONS: Zinc supplementation has no effect on morbidity from falciparum malaria in children in rural west Africa, but it does reduce morbidity associated with diarrhoea.

Validation and application of verbal autopsies in a rural area of South Africa.

OBJECTIVE: To validate the causes of death determined with a single verbal autopsy instrument covering all age groups in the Agincourt subdistrict of rural South Africa. METHODS: Verbal autopsies (VAs) were conducted on all deaths recorded during annual demographic and health surveillance over a 3-year period (1992-95) in a population of about 63 000 people. Trained fieldworkers elicited signs and symptoms of the terminal illness from a close caregiver, using a comprehensive questionnaire written in the local language. Questionnaires were assessed blind by three clinicians who assigned a probable cause of death using a stepwise consensus process. Validation involved comparison of VA diagnoses with hospital reference diagnoses obtained for those who died in a district hospital; and calculation of sensitivity, specificity and positive predictive value (PPV) for children under 5 years, and adults 15 years and older. RESULTS: A total of 127 hospital diagnoses satisfied the criteria for inclusion as reference diagnoses. For communicable diseases, sensitivity of VA diagnoses among children was 69%, specificity 96%, and PPV 90%; among adults the values were 89, 93 and 76%. Lower values were found for non-communicable diseases: 75, 91 and 86% among children; and 64, 50 and 80% among adults. Most misclassification occurred within the category itself. For deaths due to accidents or violence, sensitivity was 100%, specificity 97%, and PPV 80% among children; and 75, 98 and 60% among adults. Since causes of death were largely age-specific, few differences in sensitivity, specificity and PPV were found for adults and children. The frequency distribution of causes of death based on VAs closely approximated that of the hospital records used for validation. CONCLUSION: VA findings need to be validated before they can be applied to district health planning. In Agincourt, a single verbal autopsy instrument provided a reasonable estimate of the frequency of causes of death among adults and children. Findings can be reliably used to inform local health planning and evaluation.

Causes of death in a rural area of South Africa: an international perspective.

The study compares the cause of death profile in a rural area of South Africa (Agincourt), with that in a rural area of West Africa (Niakhar), and in a developed country with the same life expectancy (France, 1951) in order to determine causes with high and low mortality and priorities for future health interventions. In the two African sites, causes of death were assessed by verbal autopsies, whereas they were derived from regular cause of death registration in France. Age-standardized death rates were used to compare cause-specific mortality in the three studies. Life expectancy in Agincourt was estimated at 66 years, similar to that of France in 1951, and much higher than that of Niakhar. Causes of death with outstandingly high mortality in Agincourt were violent deaths (homicide and suicide), accidents (road traffic accidents and household accidents), certain infectious diseases (HIV/AIDS, tuberculosis, diarrhea and dysentery), certain chronic diseases (cancer of genital organs, liver cirrhosis, gastrointestinal hemorrhage, maternal mortality, epilepsy, acute rheumatic fever, and pneumoconiosis) and malnutrition of young children (kwashiorkor). Causes of death with lower mortality than expected were primarily respiratory diseases (pneumonia, bronchitis, influenza, lung cancer), other cancers, vaccine preventable diseases (measles, whooping cough, tetanus), and marasmus. Verbal autopsies could be used in a rural area of a developing country without formal cause of death registration to identify the most salient health problems of the population, and could be compared with a formal cause of death registration system of a developed country.

Premarital fertility in rural South Africa: a challenge to existing population policy.

The age pattern of fertility in a rural area of South Africa under demographic surveillance (Agincourt subdistrict) was investigated over the 1992-97 period. The total fertility rate (TFR) averaged 3.3 births per woman of reproductive age over the period, a major drop from earlier estimates in the same area (6.0 births in 1970-74). Age-specific fertility rates showed an atypical bimodal pattern. They were decomposed into two components of similar magnitude: premarital fertility (among women aged 12-26) and marital fertility (among women aged 15-49). The decomposition revealed the two underlying modes: a mode of premarital fertility (among women aged 18-20) and a mode of marital fertility (among women aged 28-30). Premarital fertility accounted for 21 percent of all births and for 47 percent of births among women aged 12-26. This pattern of high premarital fertility appears to reflect a low incidence of contraceptive use before the first birth, especially among adolescents, a low prevalence of abortion, and a high contraceptive prevalence thereafter. This finding calls for a reorientation of the family planning policy, which until now has targeted married women and women who have been pregnant once, but has failed to address the contraceptive needs of young women before their first pregnancy, especially adolescents.

The Agincourt demographic and health study--site description, baseline findings and implications.

OBJECTIVES: To present baseline results from first-phase demographic and health surveillance in the Agincourt field site, Bushbuckridge. To contrast findings with international data, and comment on their relevance to health development. DESIGN: Multi-round, prospective community-based study. Baseline census, 1992. SETTING: A subdistrict in South Africa's rural north-east, adjacent to the border with Mozambique. SUBJECTS: Entire population of the Agincourt subdistrict. OUTCOME MEASURES: Baseline variables for each resident included age, sex, months spent at home during 1991, mother alive/dead, highest educational standard achieved, and refugee status. A full demographic profile was constructed. RESULTS: In 1992 the subdistrict contained 57,609 persons, 26.4% of whom were Mozambican, with a population density of 148 persons per km2. Forty-four per cent were under 15 years of age, and the dependency ratio was 93%. Fertility was declining, along with a moderate decline in adult female mortality. The approximate total fertility rate was 4.0; teenage parenting was common and almost 40% of 19-year-olds had at least one child. Over 60% of men and 14% of women in the 30-49-year age group were migrants, resulting in a high proportion of single-parent households. Despite improvements, most children experienced delays in reaching primary school, and less than half made the transition to secondary school. Educational levels among Mozambican children were lower than those of local children. CONCLUSIONS: Agincourt contains a complex mix of communities comprising migrant workers, Mozambicans and a more stable permanent population. The area shares features with sub-Saharan Africa, although the mortality and fertility transitions have progressed further. Reliable, local information is essential for managing decentralised health systems.

Who dies from what? Determining cause of death in South Africa's rural north-east.

Information on cause of death is essential for rational public health planning, yet mortality data in South Africa is limited. In the Agincourt subdistrict, verbal autopsies (VA) have been used to determine cause of death. A VA is conducted on all deaths recorded during annual demographic and health surveillance. Trained lay fieldworkers interview a close caregiver to elicit signs and symptoms of the terminal illness. Each questionnaire is reviewed by three medical practitioners blind to each other's assessment, who assign a 'probable cause of death' where possible. Of 1001 deaths of adults and children identified between 1992 and 1995, 932 VAs were completed. The profile of deaths reflects a mixed picture: the 'unfinished agenda' of communicable disease and malnutrition (diarrhoea and kwashiorkor predominantly) are responsible for over half of deaths in under-fives, accidents are prominent in the 5-14 age-group, while the 'emerging agenda' of violence and chronic degenerative disease (particularly circulatory disease) is pronounced among the middle-aged and elderly. This profile shows the social and demographic transition to be well underway within a rural, underdeveloped population. Validation of VA findings demonstrate that the cause of death profile derived from VA can be used with confidence for planning purposes. Findings of note include the high death rates from kwashiorkor and violence, emerging AIDS and pulmonary tuberculosis, and circulatory deaths in the middle-aged and young elderly. A deeper understanding of the causal factors underlying these critical health problems is needed to strengthen policy and better target interventions.

Reversal in mortality trends: evidence from the Agincourt field site, South Africa, 1992-1995.

OBJECTIVE: To examine changes in mortality in rural South Africa over the period 1992-1995 by age, sex and cause of death. DESIGN: As with much of sub-Saharan Africa, South Africa lacks effective vital registration and information on mortality is lacking. The Agincourt demographic and health surveillance system was established to inform health policy and practice with regard to rural subdistrict populations. METHODS: Prospective community-based study involving annual update of a household census with enquiry into all birth, death and migration events. All reported deaths (n = 1001) are the subject of a verbal autopsy. RESULTS: An increasing trend in overall mortality relative to general population growth in the study area is apparent. There is evidence for a reversal in the previously declining trend in mortality among women 20-44 years. A comparison of 1992-1993 with 1994-1995 shows that most of the increase in mortality is concentrated in the younger adult (20-49 year) age group. AIDS and related diseases, particularly tuberculosis, appear primarily responsible. Injuries and violence (especially homicide) and circulatory disease are important, under-recognized causes of death, although their levels have remained constant over the period. CONCLUSIONS: Mortality from AIDS and related diseases appears responsible for the probable reversal in mortality emerging in South Africa's rural northeast. Findings carry implications for the emerging system of decentralized health care.

Accuracy of indirect estimates of maternal mortality: a simulation model.

A simulation model was developed to test the accuracy of indirect estimates of maternal mortality (the sisterhood method). The model generated a first generation of grandmothers, a second generation of mothers (with brothers and sisters), and a third generation of children (births). In the second generation, maternal mortality was introduced. Empirical values for the parameters of fertility and mortality were taken from a prospective survey in Senegal (Niakhar). Results based on 100 simulations of the same situation revealed several limitations of the sisterhood method: The indirect estimates could fall as far as 33 percent from the true values on individual cases; the indirect estimates tended to be systematically higher than the direct estimates; their range was wider, as were their confidence intervals; and biases were particularly strong for the younger age groups of respondents. Reasons for these biases are explored.

PIP: A simulation method was used to assess the accuracy of indirect estimates of maternal mortality (sisterhood method). The model generated a first generation of grandmothers, a second generation of mothers (with brothers and sisters), and a third generation of children (births). Maternal mortality was introduced in the second generation. Fertility and mortality parameters for the simulations were derived from a prospective study conducted in Niakhar, Senegal, in 1983-89. Results based on 100 simulations of the same situation revealed several limitations of the sisterhood method. The indirect estimates were as far as 33% from the true values on individual cases, despite the assumed perfect quality of the data. The indirect estimates tended to be systematically higher than the direct estimates, with wider ranges and confidence intervals. Biases were especially marked for the younger age group (15-39 years). The only justification for use of indirect rather than direct estimates seems to be the avoidance of questions about age differences between the respondent and the sister and the age of the sister at time of death, when applicable. Recommended, instead of indirect estimates, are two methods of computing direct estimates of maternal mortality: 1) direct computation of the maternal mortality quotient, followed by conversion to the maternal mortality rate through use of the total fertility rate, and 2) use of information on parity by age from maternity histories to compute the maternal mortality rate in each age group directly.

Direct and indirect estimates of maternal mortality in rural Burkina Faso.

A retrospective study of maternal mortality was conducted in Nouna, a rural area of Burkina Faso in 1992. Strong evidence was found of a major mortality decline among children and young adults over the 50 years preceding the study: The estimated life expectancy of 36 years in around 1945 rose to 58 years in 1991. Direct and indirect (using the sisterhood method) estimates of the maternal mortality ratio (MMR) were compared. Overall, the direct estimate of the MMR (389 deaths per 100,000 live births) for women aged 15 and older was slightly lower than the indirect estimate (428 deaths per 100,000). Taking into account the biases involved in the use of information obtained from sisters, the direct estimates indicated a marked decline in maternal mortality over time from 569 deaths per 100,000 around 1941 to 305 deaths around 1987. The validity of both data and approach, as well as the discrepancies between the direct and indirect methods, are discussed.

PIP: A retrospective study of maternal mortality was conducted in Nouna, a rural area of Burkina Faso in 1992. Strong evidence was found of a major mortality decline among children and young adults over the 50 years preceding the study: the estimated life expectancy of 36 years around 1945 rose to 58 years in 1991. Direct and indirect (using the sisterhood method) estimates of the maternal mortality ratio (MMR) were compared. Overall, the direct estimate of the MMR (389 deaths/100,000 live births) for women aged 15 years and older was slightly lower than the indirect estimate (428 deaths/100,000 live births). Taking into account the biases involved in the use of information obtained from sisters, the direct estimates indicated a marked decline in maternal mortality over time from 569 deaths/100,000 live births around 1941 to 305 deaths/100,000 live births around 1987. The validity of both data and approach, as well as the discrepancies between the direct and indirect methods, are discussed.

Risk factors for maternal mortality: a case-control study in Dakar hospitals (Senegal).

This study was conducted in the three main hospitals of Dakar, the capital city of Senegal. Each case of 152 maternal deaths identified over a 12-month period was matched with two controls: a safe delivery in the same clinic, and a safe delivery in the same neighbourhood of residence. Controls were matched on age, birth order, place, and time of delivery. The leading causes of death were: puerperal sepsis and other infections (51 cases), haemorrhage (32 cases), eclampsia (29 cases), ruptured uterus (11 cases), and anaemia (7 cases). Results of the case-control study revealed the major risk factors associated with health system failures: medical equipment failure (odds ratio [OR] = 55.0), late referral (OR = 23.2), lack of antenatal visit (OR = 16.9), and lack of available personnel at time of admission (OR = 6.6). Various indicators of maternal status at time of admission (complications, blood pressure, temperature, oedema, haemoglobin level) and of health history prior to admission (previous complications, previous C-section, lack of treatment) were also strong predictors of survival. Lastly, socio-demographic factors also appeared as correlates of maternal mortality, in particular: first pregnancy (OR = 2.3), pregnancy of high birth order (OR = 1.9), rainy season (OR = 2.4), being unmarried (OR = 2.5), and low level of education (OR = 1.6). Implications for policy are discussed.