This study examined factors associated with early weaning among Japanese women in comparison with Caucasian women in Hawaii. A mailed survey was sent to all women who delivered an infant in Hawaii between January 1st 1989 and March 31st 1989. Only Japanese (N=228) and Caucasian women (N=439) were included in this study. All Japanese breast-feeding women in the study introduced formula at some point in time. Cox multivariate regression analysis was conducted in two separate models of Japanese and Caucasian women, respectively. Higher maternal age and working part-time among Japanese women, and multiparity, college education, rural island and long-term Hawaii residence among Caucasian women were protective against early weaning. Introduction of formula was strongly associated with early weaning for both groups, the association being stronger for Japanese women. The early practice of partial breast-feeding may play an important role for early weaning among Japanese women in Hawaii.

Three groups of adolescents are compared with regard to their own considerations of abortion and when they believe abortion is justified. One group of adolescents terminated their pregnancies (n=95), a second became pregnant and carried their pregnancies to term but considered abortion (n=68), and the third also carried their pregnancies to term but did not consider abortion (n=204). The study was carried out between 1995 and 1998 in Fortaleza, Brazil. Adolescents were interviewed at the time of their hospitalization or their first prenatal visit and again at 6 weeks and 1 year post-abortion or postpartum. Friends and family recommended abortion to at least half of the teenagers in each group. Teenagers who aborted were more accepting of abortion than those who did not abort, while those who considered abortion found the practice more justified than those who did not consider abortion. Teenagers who aborted became less accepting a year later, while those who did not consider abortion became more accepting. A better understanding of adolescent attitudes towards abortion and their decision-making process should help adults and professionals meet the needs of adolescents for support in the process and in the reduction of the number of unintended pregnancies in the future.

After contraceptive use, breast-feeding duration is the major determinant of the birth interval length. Three methods of estimating births averted by breast-feeding, and the increase in contraceptive use needed to substitute for breast-feeding, are presented. Method 1 simply utilizes Bongaarts’ Ci, and the other two are based on mean birth intervals with and without breast-feeding. Estimates for each method are derived for six countries with DHS surveys from the mid-1990s: Burkina Faso, Uganda, India, Indonesia, Brazil and Peru. The estimated percentage of additional births that would occur if there were no breast-feeding ranged from 1–4% in Brazil to about 50% in Burkina Faso and Uganda, reflecting very low breast-feeding in Brazil and very high levels in the sub-Saharan African nations. Strengths and limitations of the three methods are considered.

The final estimate of South Africa's population as of October 1996 from the first post-apartheid census by Statistics South Africa was lower (40·6 million) than expected (42 million). The expectation of a total population of 42 million was largely based on results of apartheid projections of South Africa's population. The results of the last apartheid census in South Africa in 1991 had been adjusted such that it was consistent with results modelling the population size of South Africa. The discrepancy between the final estimate of the 1996 census and that expected from the modelling described above, and the departure by Statistics South Africa from previous practice of adjusting the census results to be consistent with demographic models, has generated controversies regarding the accuracy of the final results from the 1996 census. This study re-examines levels and differential in fertility in South Africa from recent evidence in order to assess whether or not the fertility inputs in projections of South Africa's population during the apartheid era overestimated fertility.

The social environment and exposure to life challenge affect a person's physical and emotional well-being. The present research uses a population-based study of the elderly in Taiwan to elaborate the cumulative physiological costs – as reflected in biological markers of risk factors known to have adverse consequences for health – of challenge and unfavourable position in social hierarchies and networks. Overall, biological markers of risk among the elderly are similar in Taiwan and the United States. However, male and female Taiwanese elderly are at lower risk for illness associated with indicators of DHEA-S, while women are at higher risk for illness associated with elevated blood pressure, and men at lower risk for illness associated with total/HDL cholesterol, and glycosylated haemoglobin. There are strong and statistically significant effects of position in social hierarchy (education) and challenge (recent widowhood and a perception of high demands) on an index of cumulative risk (allostatic load). Membership in social networks and participation in social activities have expected, but not statistically discernible, effects.

The present paper is based on information on marital patterns and reproductive performance (reconstituted families) in the rural community of Los Nogales, Galicia, Spain. Biodemographic data were used to analyse temporal changes and structure of consanguinity in the population, as well as consanguinity versus reproductive success. Of 2347 marriages celebrated between 1871 and 1977, 5·15% were between relatives (up to third degree). The population’s inbreeding coefficient was above the Spanish average after 1890, and levels were high during the first part of the 20th century. A possible underestimation of inbreeding coefficients is attributed to the elevated frequency of extramarital births occurring in the Los Nogales population (13·47%). The structures of consanguineous matings, expressed as C22/C33 and C33/C44, turned out to be 0·86 and 0·82 respectively. Regarding migration, before 1920 consanguinity increased, but net migration was negative. In the period 1920–1929 consanguinity began to decrease, prior to maximum emigration. As for reproductive success, information from 1503 reconstituted families shows that complete fertility was slightly higher among consanguineous families despite a greater infant mortality. Lower infertility in consanguineous matings, as well as lower age at marriage and first maternity, could explain the above results.

The use of contraceptives has become prevalent among females in Thailand in the past 20 years, and oral contraceptive use has been suggested to trigger changes in fat intake, energy expenditure, fat metabolism and blood pressure. Based on field investigations of 391 married women aged 20 years or over in Yasothon Province, North-east Thailand, this study aims to elucidate the effects of oral contraceptive use on body mass index (BMI: kg/m2 ) and blood pressure, taking into account reproductive histories and socioeconomic conditions. The proportion of obese (BMI> 25) subjects was high in the age groups 30–39, 40–49 and 50–59, accounting for, respectively, 39·4%, 51·1% and 48·5% of these populations. The proportion of women with hypertension (90/140 mmHg) was 23·7%, 18·5% and 26·2% in the 40–49, 50–59 and 60–69 age groups. Current contraceptive practices in the studied population included sterilization by operation, oral contraception and injection. These methods accounted for 43·0%, 12·8% and 8·2% of the population, respectively. Sociodemographic factors such as reproductive history, years of education and household income were not significantly related to BMI or to blood pressure (ANOVA with age adjustment). In contrast, oral contraceptive users had significantly higher BMIs and diastolic blood pressures (p<0·01, ANOVA with age adjustment). Multiple regression analysis also revealed that oral contraceptive use was a weak but significant contributing factor to both high BMI and blood pressure when sociodemographic factors were taken into account and controlled for statistically. It can thus be concluded that the use of contraceptive pills, which contain oestrogen and progestin and are provided free of charge to Thai women, tend to increase BMI and to elevate blood pressure.

This study evaluated the strength of the independent effects of social position (expressed by educational level) and number of childbirths on body mass index (BMI) variation of Polish adult females. The material comprised 2045 pre-menopausal women aged 35–50, who were healthy and occupationally active inhabitants of the city of Wrocław, Lower Silesia, Poland. Two-way analysis of variance (ANOVA) revealed that both educational level (F=34·7; p=0·0001) and parity (F=5·6; p=0·001) exerted independent significant effects on BMI. The mean BMI of women who had attended basic vocational or trade school at the very most (27·0 kg/m2) was greater than that of women who had completed secondary school education or had graduated from university (25·3 kg/m2). However, it is worthy of note that there were no social differences in BMI values between childless women. Nevertheless, an increasing number of childbirths was essentially related to increasing female BMI in each social group, and this tendency was most marked among women of lower social position. Regardless of educational level, the highest prevalence of obesity (BMI exceeding 30 kg/m2) was found among females with at least three children (15·6% and 26·4% of women from higher or lower social groups, respectively).

Final body height is achieved as the result of a combination of genetic and environmental factors. The aim of this article is to review past studies on body height that have followed different scientific traditions. In modern Western societies, about 20% of variation in body height is due to environmental variation. In poorer environments, this proportion is probably larger, with lower heritability of body height as well as larger socioeconomic body height differences. The role of childhood environment is seen in the increase in body height during the 20th century simultaneously with the increase in the standard of living. The most important non-genetic factors affecting growth and adult body height are nutrition and diseases. Short stature is associated with poorer education and lower social position in adulthood. This is mainly due to family background, but other environmental factors in childhood also contribute to this association. Body height is a good indicator of childhood living conditions, not only in developing countries but also in modern Western societies. Future studies combining different scientific traditions in auxology are needed to create a more holistic view of body height.

This study analyses the social, physiological and motivational determinants of sexual activity for 644 married women in rural areas of Osun State, Nigeria. The data come from the Fertility Awareness and Pregnancy Avoidance study conducted in 1993–94. Sexual activity is measured by three continuous variables: weekly frequency of (1) total sexual activity, (2) coital-only sex and (3) both coital/non-coital sex. Analyses of variance were performed to test the difference in group means between the predictor variables and measures of sexual activity. Ordinary least squares regression analyses were then performed for the three dependent variables. Two models are used: the first contains only those variables associated with an individual’s demographic, social and economic status, and the second adds predictor variables associated with motivational and physiological factors. Results show that while many socioeconomic variables by themselves are significantly associated with sexual activity measures, the addition of physiological and motivational variables weakens their effects and lessens their original statistical significance. Additionally, the socioeconomic and demographic factors associated with frequency of sexual activity are not necessarily the same ones significantly associated with coital-only or combined coital/non-coital sex. While other studies have tended to focus either on socioeconomic or physiological factors, the joint examination of both types of influences seems to indicate that the latter have more proximate effects on the frequency of both coital and non-coital sexual activity of married women in this population. Contraceptive protection is shown to be highly positively associated with all three of the sexual activity measures, empirically confirming the important relationship between contraception and both coital and non-coital forms of sexual activity.

This study was carried out to quantify secular trends in seasonal variation in births in Malta, a small Mediterranean country where the vast proportion of births occur in wedlock due to a predominantly Roman Catholic population. It also related such variations to seasonal variation in marriages. Annual seasonal peaks of marriages and births were analysed over the period 1950–1996 by X11 ARIMA. A significant peak in marriages (n=111,932) in the third quarter of the year was found for almost the entire period under study. This was paralleled by a peak in births (n=299,558) for the period 1970–1996, which lagged after the peak in marriages by 13–14 months. For the period 1994–1996, when monthly data for monthly pregnancies were available by pregnancy order, the peak in births was caused by first pregnancies only. Seasonal patterns in births occur almost universally due to cultural and/or biometeorological factors. The best known patterns include those of the southern United States, where births decline in April and May, and in northern Europe, where births peak in March and April. In Malta, the late summer peak in births appears to be due to a practical and planned approach by Maltese couples to contraceptive planning, probably influenced by the Roman Catholic ethos and social pressures, with unprotected intercourse occurring only after marriage. In Malta, birth control, albeit by so-called natural methods, was introduced in the 1960s. Prior to this period, births peaked towards the beginning/end of the year, and this may be the more natural seasonality of births in Malta.

The purpose of this study was to investigate whether the well-established relationship between parity and birth weight is affected by the sex composition of siblings, especially for male newborns. Subjects were 856 male and 862 female newborns who weighed at least 2500 g at birth, who were born after 37 completed weeks of gestation, who obtained an Apgar score of 7 or higher, who had the same biological parents as all other children in the sibship, and who lived in the same household. Information on birth weight was collected from hospital records. Results showed that male newborns with older brothers weighed less than male newborns with older sisters. In contrast, the weight of female newborns with older brothers did not differ from the weight of female newborns with older sisters. One explanation of these results is that maternal immunoreactivity to some male-specific feature of the fetus affects prenatal development and consequently reduces birth weight in males. The relation between older brothers and birth weight may have theoretical significance for behavioural variables.

This paper explores the relationship between body mass and risk of death among US adults. The National Health Interview Survey–Multiple Cause of Death linked data set is used for the years 1987–1997, and Cox proportional hazard models are employed to estimate the association between obesity, as measured by the body mass index (BMI), and overall, circulatory disease-specific and diabetes-specific mortality. A U-shaped relationship is found between BMI and overall mortality. Compared with normal weight individuals, mortality during the follow-up period is 34% higher among obese class II individuals and 77% higher among obese class III individuals, controlling for age and sex. A J-shaped relationship exists between circulatory disease mortality and obesity, with a slightly higher risk of death for all categories of BMI. The relationship between BMI and diabetes mortality is striking. Compared with normal weight individuals, obese class I individuals are 2·8 times as likely to die, obese class II individuals are 4·7 times as likely to die, and obese class III individuals are 9·0 times as likely to die of diabetes during the follow-up period, controlling for age and sex. These results demonstrate that obesity heightens the risk of overall and circulatory disease mortality, and even more substantially increases the risk of diabetes mortality. These mortality findings, together with the substantial recent increases in obesity, lend urgency to public health programmes aimed at reducing the prevalence and consequences of obesity.

The study analyses various sex differences observed among children in WFS and DHS surveys conducted in sub-Saharan Africa. Four outcome indicators are presented: neonatal mortality, postneonatal mortality, child mortality and prevalence of malnutrition. Three indicators of health seeking behaviour are presented: vaccination, oral rehydration therapy and duration of breast-feeding. The statistical analysis focuses on comparison of the observed distributions of the sex ratios to theoretical distributions expected from the sample sizes of the various surveys. The results show the absence of any difference in health seeking behaviour between boys and girls, whether for preventive medicine (vaccination), curative medicine (oral rehydration therapy) or feeding practices (breast-feeding). On the other hand, mortality appears to be consistently higher for boys, more so among neonates (+28%) than among 1–12-month-olds (+8%) and 1–4-year-olds (+4%), and similarly malnutrition appears to be more prevalent among boys (+5%). The contrast between the lack of differences in behavioural indicators and the significant differences in outcome indicators suggests a biological causality. Results are discussed in the light of biological factors.

Annual changes in twinning and triplet rates by zygosity were investigated in eight countries during the period 1972–1999 using vital statistics. The monozygotic (MZ) twinning rates in Denmark, Switzerland and the Slovak Republic remained more or less constant throughout this period, whereas those in England and Wales, the Federal Republic of Germany (Germany), the Netherlands, the Czech Republic and Japan increased significantly year by year. With the exception of the Slovak Republic, the dizygotic (DZ) twinning rate increased significantly year by year in each country. It was 2·9 times higher in Denmark and 1·5 times higher in Germany in 1999 than in 1972, and within the same range in the other countries. With two exceptions, the MZ triplet rates remained more or less constant in each country. On the other hand, the DZ and trizygotic (TZ) triplet rates increased significantly year by year in each country. The TZ rate increased 30-fold in Germany, 16·6-fold in Japan, 11·7-fold in Switzerland, 9·7-fold in the Czech Republic, 8·7-fold in the Netherlands, 6·4-fold in Denmark, 5·6-fold in England and Wales and 3·5-fold in the Slovak Republic. The higher DZ twinning rate and higher DZ and TZ triplet rates since 1983 have been attributed to the higher proportion of mothers being treated with ovulation-inducing hormones and in vitro fertilization (IVF) in Denmark, England and Wales, Germany, the Netherlands, Switzerland and Japan. After the introduction of fertility drugs and IVF, variations in the DZ twinning and triplet rates and the TZ triplet rates were not only due to biological factors, but also depended on the popularity of fertility drugs and IVF in each country. In the Slovak Republic, where human fertility might not be affected by some adverse environmental factors, the DZ:MZ ratio remained constant during the period 1972–1999.

This study examines the relationship between blood pressure and the religious practices of Kuwaitis as members of a Muslim society. Religious variables were measured via a sociocultural questionnaire. Blood pressure measurements were taken with a sphygmomanometer. Non-opportunistic samples were taken from 223 Kuwaitis. The difference in religious commitment between Muslim Sunnis and Muslim Shiites was examined using a t-test. Matrix correlation was used to examine the relationship between religious commitment and some other variables. Multiple regression was conducted to determine the effect of religiosity on blood pressure, as well as statistically controlling for other variables such as body mass index, socioeconomic status, smoking, gender and age. It was found that both systolic and diastolic blood pressure were affected by religious commitment and religious activities.

Studies of human mate choice have been based almost exclusively on stated preferences and personal advertisements, and the external validity of such studies has therefore been questioned. In the present study, reallife matings based on a large representative sample of newly wed couples in 1998 (n=66,598) were analysed according to educational assortative mating. The results demonstrate a strong educational homogamy in this national Portuguese sample. However, men tend to marry women who are slightly more educated than themselves. The results are compared with those of a modern society (US, 1940–87) and a traditional society (Kipsigis, 1952–91). Since educational attainment is strongly associated with social status and intelligence, these results are discussed in an evolutionary perspective.

This study examines the extent of the interrelationship between future fertility intention and subsequent fertility behaviour in rural Bangladesh using longitudinal data. It confirms that fertility intention is an important predictor of subsequent fertility behaviour for rural Bangladeshi women. Women wanting no more children are over three times less likely to have a child during a 5-year follow-up than those wanting more children. A multivariate model using logistic regression shows that fertility intention is a useful indicator for fertility behaviour, when background and life-cycle variables are controlled. The different patterns of fertility intentions by socioeconomic and demographic subgroups suggest that different programme strategies should be designed for specific target groups.

The role of family health-seeking behaviour in under-five-year child mortality was explored through the combined approach of examining health-seeking behaviour regarding treatment generally, and in specific in relation to illness before death. A population-based case control study was carried out during the period 1993–1994 using 222 deaths from diarrhoea and acute respiratory illness (ARI) in children under five years of age in six slums of Karachi as cases, and 419 controls matched on age, disease (diarrhoea and ARI) and slum. Factors significantly associated (p<0·05) with child mortality in the multivariate analysis were: mothers changing healers quickly, using a traditional healer or an unqualified doctor and mothers to whom doctors did not explain the treatment, even when maternal education was controlled for. Seeking effective medical services is highly influential on whether the child survives or succumbs to ARI or diarrhoea. As mothers are the first providers of care, an attempt should be made to try and improve their skills through health education so that they can use simple and effective treatments for minor illnesses. They should also be taught to recognize potentially life-threatening conditions, to seek care early and to persist with treatment.