There is some evidence, mostly of an epidemiological nature, that coital rates may be positively associated with dizygotic twinning. It is suggested that this link is causal, in which case an explanation becomes available for some curious—and hitherto unexplained—features of dizygotic twinning rates by maternal age and legitimacy.

This study aimed to assess the prevalence of and risk factors associated with alcohol abuse among women and men in Moshi in northern Tanzania. Alcohol abuse was measured by a CAGE score of 2–4, versus 0–1 for no alcohol abuse (Ewing, 1984). Crude and adjusted logistic regression models determined odds ratios (OR) and 95% confidence intervals (95% CI) of alcohol abuse by characteristics of, respectively, women with partners (n=1200), women without partners (n=614) and men (n=788) (women’s partners). Prevalence of alcohol abuse was 7·0% (95% CI: 5·6–8·4) among women with partners, 9·3% (95% CI: 7·0–11·6) among women without partners, and more than double among men at 22·8% (95% CI: 19·9–25·8). In general, Christians had higher alcohol abuse than Muslims or other religions, as did Chagga men compared with men of other ethnic groups. Other socio-demographic characteristics, such as education or income, were not significant. Sexual behaviours were significant predictors of alcohol abuse. For example, women without partners who reported more than two partners in the last year had higher alcohol abuse compared with women reporting no partners (OR=8·75; 95% CI: 2·37–32·31), as did men reporting it is ‘OK to hit a partner’ for any reason (OR=1·79; 95% CI: 1·16–2·77) compared with men who did not. HIV-1 infection was not significantly associated with alcohol abuse by women or men. The Christian Church in Moshi should consider raising awareness about the harmful effects of high alcohol use among its adherents. Comprehensive programmes focusing on reducing number of partners and alcohol use, particularly by men, are needed in this community.

Anthropometric and sociodemographic variables were taken from 4320 children in a baseline survey carried out in March–April 1988 in the district of Mbarara, south-west Uganda. After 12 months a follow-up survey assessed the mortality of the children during the preceding year. Lack of ownership of cattle, recent arrival in the village, using candles for lighting, being of birth order higher than 5 and having a father with less than 8 years of schooling were significantly associated with child mortality. The addition of mid-upper arm circumference significantly improved the logistic model of socioeconomic variables and mortality and did not diminish the predictive power of socioeconomic variables in relation to increased mortality. This suggests that nutritional status and specific socioeconomic factors are both, independently, important predictors of child mortality.

A fundamental public health strategy to reduce the risk of HIV/AIDS is to increase levels of awareness and knowledge about the disease. Although knowledge about HIV/AIDS and protective sexual behaviour are linked theoretically, relatively little is known about their empirical relationship. Using Demographic and Health Survey data from 23 low- and middle-income countries, this study used multilevel logistic regression models: to examine cross-national variability in the relationship between HIV/AIDS knowledge and protective behaviour (condom use and restricted sex); to investigate the moderating influences of women’s educational attainment on this relationship; and to test the extent to which severity of the HIV/AIDS epidemic accounts for cross-national variability in the association between HIV/AIDS knowledge and protective behaviour. There was an association between increased knowledge of HIV/AIDS and condom use that varied in strength and form cross-nationally. This cross-national variation was accounted for partially by the socioeconomic characteristics of women resident in the study countries and between-country differences in the severity of the HIV epidemic. While education modified the association between HIV/AIDS knowledge and protective behaviour – stronger associations at lower levels of education – epidemic severity exerted a stronger influence on behaviour than any other characteristic. Finally, this study indicates that protective sexual practices are disturbingly low. In eight of 23 countries, overall levels of condom use to prevent STDs and HIV/AIDS were less than 5·0%. Waiting for the spread of HIV/AIDS infection to change sexual practices in low- and middle-income countries will result in dramatic unnecessary suffering.

Among the Kipsigis, a population of south-western Kenya who do not use contraception, age at menarche and age at last live birth could be determined for a cohort of post-menopausal women, through reference to clitoridectomy ceremonies that can easily be dated. While a woman's age at last live birth was strongly associated with the length of her reproductive lifespan, completed family size was better predicted by age at menarche. The demographic implications of variation in menarcheal age are discussed.

Over the past century, the population of Korea has aged rapidly as a result of decreasing fertility and mortality. Furthermore, the percentage of the population aged 65 and older is expected to double from 7% to 14% within 18 years, a much shorter doubling period than in most other developed countries. As Korean society ages, interest in healthy and successful ageing has increased. However, although previous studies have examined various determinants of successful ageing, such as socioeconomic status, gender differences have been neglected. This study investigated gender differences as factors in successful ageing among elderly men and women. Successful ageing has been defined as having high levels of physical and social functioning. Physical functioning includes having no difficulties with activities of daily living (ADL) or instrumental activities of daily living (IADL). Social functioning is defined as participation in at least one of the following social activities: paid work, religious gatherings or volunteer service. Data for this study were obtained from a representative sample of 761 community-living individuals aged 65–84 years (340 males, 421 females); the respondents were interviewed face-to-face as part of the third wave of the Hallym Ageing Study (2007). Socioeconomic status appears to have a greater gender-specific effect on physical functioning than on social functioning. Especially for elderly men, a higher monthly individual income was significantly related to a higher level of physical functioning. Among elderly women, a higher level of education was associated with a higher level of physical functioning. In a major metropolis, elderly men had low social functioning and elderly women had low physical functioning. As Korea's population ages, successful ageing has received much attention. This study shows that policies promoting successful ageing must consider gender differences and associated socioeconomic factors.

A study has been made in a group of rural Oxfordshire villages of levels of similarity between husbands and wives for IQ, personality and some anthropometric characteristics. Significant levels of assortative marriage have been found in both verbal and performance IQ, personality ‘inconsistency’, stature, weight and some other bodily dimensions. Their nature has been analysed by time of marriage, birthplace and social class, all of which appear to have marked effects. On the other hand, length of courtship and distance apart of the partners' residences at marriage seem to be more or less inconsequential.

A study was conducted in Dakar, Senegal, to measure reproductive health knowledge and contraceptive use among young adults, and access to family planning services. A household survey was conducted with 1973 single and married women aged 15–24 and 936 single men aged 15–19. Two focus groups and a simulated client study were also conducted. The survey and focus groups noted gaps in knowledge of family planning methods and reproductive health. There were misconceptions about methods and only one-third of men and women aged 15–19 correctly identified the time of the menstrual cycle when a women is most likely to get pregnant. Contraceptive use at time of first premarital sexual experience was less than 30%. The simulated client study noted many barriers to services. ‘Clients’ felt uncomfortable in the clinics and felt that providers were reluctant to take care of them. None of the ‘clients’ who requested contraception received it.

Female- and male-headed households were compared using data from a Demographic and Health Survey conducted in Tanzania in 1996. Chi-squared tests showed that sex of head of household was highly significantly associated with: residence, household size and composition, radio ownership, having enough food to eat, and age and marital status of head of household. An analysis by the logit regression model showed that female-headed households were more likely than male-headed households to be in rural areas, be small, have fewer men, not have radios and not have enough food to eat. The majority of female heads of households were unmarried and older than male heads of households. The implication is that female-headed households are poorer than male-headed households.

This paper examines the effects of a child's place of birth, mother's education, region of residence and rural and urban residence on infant mortality in Nigeria between 1965 and 1979, using data from the 1981/82 Nigeria Fertility Survey. Infant mortality rates declined in all regions between 1965 and 1979. Children born in modern health facilities, irrespective of their mothers' place of residence, experienced significantly lower rates of infant mortality than those born elsewhere. Logistic regression analysis showed that all other variables tested were also significant, although some to a lesser degree. Efforts to reduce infant mortality in Nigeria should include policies that rectify rural and urban differentials in the distribution of health facilities and encourage their use.

Immigration, immigration policies and education of immigrants alter competence levels. This study analysed their effects using PISA, TIMSS and PIRLS data (1995 to 2012, N=93 nations) for natives' and immigrants' competences, competence gaps and their population proportions. The mean gap is equivalent to 4.71 IQ points. There are large differences across countries in these gaps ranging from around +12 to −10 IQ points. Migrants' proportions grow roughly 4% per decade. The largest immigrant-based ‘brain gains’ are observed for Arabian oil-based economies, and the largest ‘brain losses’ for Central Europe. Regarding causes of native–immigrant gaps, language problems do not seem to explain them. However, English-speaking countries show an advantage. Acculturation within one generation and intermarriage usually reduce native–immigrant gaps (≅1 IQ point). National educational quality reduces gaps, especially school enrolment at a young age, the use of tests and school autonomy. A one standard deviation increase in school quality represents a closing of around 1 IQ point in the native–immigrant gap. A new Greenwich IQ estimation based on UK natives' cognitive ability mean is recommended. An analysis of the first adult OECD study PIAAC revealed that larger proportions of immigrants among adults reduce average competence levels and positive Flynn effects. The effects on economic development and suggestions for immigration and educational policy are discussed.

Are risk behaviours in adolescence differentiated according to same-sex vs opposite-sex interest? For all respondents a five-point scale of interest in each sex used information from both of the first two in-home waves of the National Longitudinal Study of Adolescent Health (Add Health). Logistic regression predicted the probability of experiencing each risk behaviour from the same-sex and opposite-sex interest scores. Same-sex interests have more effect on emotional risk, and opposite-sex interests have more effect on substance use. Nevertheless, all risk variables except boys’ depression are responsive to both same-sex and opposite-sex interest. The same-sex interest component of risk is attributed to the emotional strain of living with an anomalous sex interest in a heterosexual society.

Using a sub-sample of ever-married women from the 1993 Ghana Demographic and Health Survey (GDHS), this study examines differentials in contraceptive use in six cultural groups: Ga-Adangbe, Twi, Fante/other Akans, Ewe, Guan/others and Mole-Dagbani. Multivariate analysis is used to explore whether reported ethnic differentials in contraceptive use can be attributed to ethnicity or to other characteristics that distinguish the ethnic groups. Overall, the findings are generally more consistent with the 'characteristics' hypothesis, because contraceptive use differentials by ethnic group is accounted for by differences in socioeconomic and demographic characteristics of these women. However, for the Fante/other Akans, even after the necessary controls, ethnicity continued to emerge as a significant determinant of contraceptive use. Programmatic implications of these results are discussed.

Based on the authors’ interview survey for 608 randomly selected women of the rural Arab population in the South Ghor district of Jordan, this paper examined the effects of polygyny and consanguinity on high fertility, which was recognized as natural fertility. The prevalence of polygynous and consanguineous marriages was 28·0% and 58·1%, respectively, largely reflecting the population’s traditional marriage customs. The findings highlighted a significantly higher total marital fertility rate (TMFR) in the monogamous wives (10·5) than in the senior polygynous (8·1) and junior polygynous wives (8·6); the TMFR did not significantly differ among the wives of non-consanguineous, first-cousin and second-cousin marriages. The formation of polygynous marriage was decided by the husband, mostly as a result of his senior wife’s infecundity or sub-fecundity, and the age of the husband at marriage to his junior polygynous wife was high in many cases, leading to a decline in this wife’s fecundity.

Data from the 1998–99 National Family Health Survey (NFHS2) of India are used to examine the net effects of social and demographic characteristics of women on the likelihood of abortion while emphasizing important differences between women from northern and southern states. A north–south comparison illustrates that southern women have relatively higher levels of literacy and labour force participation, lower levels of son preference, and smaller family size. Results from logistic regression analyses show that literacy, type of work, belonging to a scheduled caste or tribe, urban residence, standard of living, parity, religion, age, age at union and contraceptive behaviour all have significant effects on the likelihood of abortion. However, most of these effects significantly differ for southern and northern women. Moreover, the effects of agricultural work, son preference and age at union on the likelihood of abortion are significant for northern but not southern women.

This study aimed to understand access to maternal health care and the factors shaping it amongst poor migrants in Mumbai, India. A cross-sectional mixed methods approach was used. It included multistage cluster sampling and face-to-face interviews, through structured interview schedules, of 234 migrant women who had delivered in the two years previous to the date they were interviewed. Qualitative in-depth interviews of migrant women, health care providers and health officials were also conducted to understand community and provider perspectives. The results showed that access to antenatal care was poor among migrants with less than a third of them receiving basic antenatal care and a quarter delivering at home. Multivariate analysis highlighted that amongst migrant women those who stayed in Mumbai during pregnancy and delivery had better access to maternal health care than those who went back to their home towns. Poor maternal health care was also due to weaker demand for health care as a result of the lack of felt-need among migrants due to socio-cultural factors and lack of social support for, and knowledge of, health facilities in the city. Supply-side factors such as inadequate health infrastructure at primary and secondary levels, lack of specific strategies to improve access to health care for migrants and cumbersome administrative procedures that exclude migrants from certain government programmes all need to be addressed. Migrants should be integral to the urban development process and policies should aim at preventing their exclusion from basic amenities and their entitlements as citizens.

A fertility survey of unmarried adolescents and young adults (953 males and 829 females) in Greater Accra and Eastern regions of Ghana revealed that a substantial proportion of the respondents were sexually experienced. Overall, 66·8% of the males and 78·4% of the females were sexually experienced. The mean ages (±SD) of the males and females were 15·5±2·5 and 16·2±2·0 years, respectively. Most respondents claimed to have received adequate information on reproductive health and sexually transmitted diseases (STDs), including AIDS. However, 20% and 30% of the respondents in peri-urban and rural areas, respectively, did not know that a girl could get pregnant the first time she has sexual intercourse. The incidence of pregnancy among the unmarried female respondents was relatively high (37%), and was higher in urban than in rural areas. Approximately 47% of those who had ever been pregnant reported that they had had an abortion. Levels of contraceptive awareness were high (98·2% among males and 95·5% among females) but many still engaged in unprotected sexual relations. The most commonly used methods were the condom and the pill. The main reasons given for non-use were that they did not think about contraception, were concerned about the safety of contraceptives, and partner objection. These findings point to the need for targeting of unmarried adolescents and young adults with information on reproductive health and family planning to increase their awareness of the risks of pregnancy, STDs and HIV infection.

Obesity has been linked to several physiological and psycho-social diseases, decreases in cognitive function, poor levels of scholastic achievement, low socioeconomic status and delayed onset of maturity. This study investigates the association between obesity and both academic performance and reasoning ability in 394 male and 398 females students between the ages of 6 and 12 from Lisbon, Portugal. It also assesses how this relationship may be influenced by chronological age, maturity and socioeconomic status. The results suggest that: 1) reasoning ability is independent of socioeconomic status and level of maturity; 2) no differences in reasoning ability exist between groups of different BMI; 3) academic performance is moderated by chronological age in boys, and by maturity in both genders; 4) obesity is not associated with academic performance. It is concluded that reasoning ability and academic performance are not associated with obesity, and that inter-individual differences in academic performance in boys may be explained by differences in their level of maturity.

The aim of the present study was to estimate the prevalence and examine the determinants of consanguineous marriage types in India. Data for 456,646 ever-married women aged 15–49 years were analysed from the National Family Health Survey (NFHS)-4 conducted in 2015–16. The overall prevalence of consanguineous marriage was 9.9%; the South region (23%) and North-East region (3.1%) showed the highest and lowest prevalences, respectively. Muslims had a higher prevalence (15%) than Hindus (9%). The prevalence of first cousin marriage (8.7%) was more than that of second cousin (0.7%) and of uncle–niece marriages (0.6%). Women living in urban areas and in nuclear families, having a higher level of education and belonging to affluent families were less likely to marry their cousins (p < 0.01). Women living in the South region of the country were more likely to marry their cousins, as well as uncles (p < 0.001). Close scrutiny of the trends in the results (odds ratios) revealed no clear relationship between socioeconomic condition and consanguineous marriage. The study results suggest that religion and north–south regional dichotomy in culture largely determine consanguineous marriage rather than socioeconomic condition in India.

Women's social networks and social power are increasingly seen as important factors modulating their health in sub-Saharan Africa. Polygyny, a common marital structure in many societies, mediates important intra-household relationships by requiring both competition and co-operation among co-wives. Using mixed methods, semi-structured questionnaires were administered to 298 women aged 15–84 living in the Kolondiéba region of rural Mali in 1999, and supplemented by detailed interviews with 40 women. Three categories of outcome were explored: illness experience, therapeutic itinerary and social support received. Quantitative data were analysed using regression analysis and qualitative data using a grounded theory approach. In quantitative analyses, controlling for age and household wealth index, senior wives were less likely to be escorted to a healer by their husbands during illness than were junior wives or monogamous women. Polygynous women were also less likely to obtain a treatment for which there was a monetary fee. Fewer than one-third of polygynous women reported the assistance of a co-wife during illness in any given task. In qualitative analyses, women further related varied mechanisms through which polygyny impacted their health trajectories. These ranged from strongly supportive relationships, to jealousy because of unequal health or fertility, bias in emotional and material support provided by husbands, and accusations of wrong-doing and witchcraft. This study highlights the need for more prospective mixed methods analyses to further clarify the impact of polygyny on women's health-related experiences and behaviours in sub-Saharan Africa.