Women in almost all modern populations live longer than men. Research to date provides evidence for both biological and social factors influencing this gender gap. Conditions when both men and women experience extremely high levels of mortality risk are unexplored sources of information. We investigate the survival of both sexes in seven populations under extreme conditions from famines, epidemics, and slavery. Women survived better than men: In all populations, they had lower mortality across almost all ages, and, with the exception of one slave population, they lived longer on average than men. Gender differences in infant mortality contributed the most to the gender gap in life expectancy, indicating that newborn girls were able to survive extreme mortality hazards better than newborn boys. Our results confirm the ubiquity of a female survival advantage even when mortality is extraordinarily high. The hypothesis that the survival advantage of women has fundamental biological underpinnings is supported by the fact that under very harsh conditions females survive better than males even at infant ages when behavioral and social differences may be minimal or favor males. Our findings also indicate that the female advantage differs across environments and is modulated by social factors.

https://www.pnas.org/content/pnas/early/2018/01/03/1701535115.full.pdf

Women live longer than men even during severe famines and epidemics

The current worldwide decline in the initiation and duration of breastfeeding has increased the need for effective breastfeeding promotion. Promotion policies and programs need to be sensitive to those factors that may help or hinder a mother in her efforts to breastfeed. Such factors include sociodemographic characteristics, maternal employment, and social support. Social support that increases breastfeeding includes emotional, tangible, and educational components from both informal social network members (male partner, mother, family/friends) and professional network members (health care professionals, lactation consultants). Conversely, negative social support may decrease breastfeeding.

The Role of Social Support in Breastfeeding Promotion: A Literature Review

Differences internationales. Zones urbaines et rurales. La frequence de la maladie a-t-elle change? Etiologie infectieuse. Facteurs genetiques. Frequence chez les juifs. Regime. Mortalite. Maladie de Crohn et cancer

https://gut.bmj.com/content/gutjnl/25/8/886.full.pdf

Epidemiological aspects of Crohn's disease: a review of the literature.

Background. Extended breastfeeding is known to benefit the health of children in developing countries and despite widespread expectations of a decline in breastfeeding in these countries, it has been demonstrated that the incidence and duration of breastfeeding are in fact increasing in many countries. Methods. In this paper, trends in breastfeeding duration are examined in 15 developing countries, using data from two comparable surveys for each country, the World Fertility Survey (conducted in the late 1970s) and the Demographic and Health Survey (conducted in the late 1980s). Multivariate regression models are used to examine differentials in breastfeeding behaviour across population subgroups in these countries for each time period, and these differentials are used to determine the extent to which the observed trends are due to changes in population characteristics and to what extent behaviour has changed within population subgroups. Results. Results show that changes in the characteristics of the population have almost universally pushed breastfeeding durations in a downward direction. On the other hand, trends within population subgroups have been positive in all but two of the 15 countries examined. Conclusions. Changes in population characteristics can be expected to continue for most developing countries, exerting a downward pressure on breastfeeding. Policies that promote breastfeeding are needed to counter these changes, especially in the most vulnerable population subgroups.

The Effect of Changes in Population Characteristics on Breastfeeding Trends in Fifteen Developing Countries

This paper examines the question of why the total fertility rate of the !Kung San hunter-gatherers of the Northern Kalahari desert is as low as 4.69 births. When the intermediate variables involved are examined through the employment of a reproductive equation, it becomes clear that low fecundity is a major issue. Arguments offered previously to explain the low fertility of !Kung women, depending on factors such as nutrition, health status, and lactational practices are insufficient. Drawing upon recent data from sports medicine and endocrinology, I suggest that the pattern of San female energetics in their gathering and subsistence routine has a direct effect upon their fecundity. Such a correlation between activity patterns, endocrine function, and reproductive capacity may also be important for understanding the fertility of other mobile hunter-gatherer groups.

Hunter-Gatherer Energetics and Fertility: A Reassessment of the !Kung San

Studies show that breastfeeding is ideal for infant nutrition and is an important means of spacing births Breast milk provides some immunological protection to the infant protects against infection and malnutrition satisfies the infants nutritional needs and costs less than other feeding substitutes Breastfeeding also protects against pregnancy although the length of the contraceptive effect cannot be predicted Analysis of breastfeeding trends and patterns shows that although most women in developing countries initially breastfeed their children the length of breastfeeding is declining especially in urban areas The practice of breastfeeding in contrast appears to be increasing in some developed countries after several decades of decline Breastfeeding trends and patterns may be influenced by the following sociodemographic factors: 1) urban-rural residence 2) parental education and socioeconomic status 3) mothers age and parity 4) support from family and friends 5) mothers employment and 6) contraceptive use Biological scientists and demographers are unanimous in concluding that although breastfeeding substantially contributes to birth spacing and fertility control in many areas it is an unreliable means of contraception Breastfeeding women are therefore advised to seek alternative means of contraception to avoid pregnancy The effects of hormonal contraception on breastfeeding have not been established but the following points can be made: 1) combined estrogen-progestin oral pills decrease milk volume in some cases 2) progestin-only contraception does not affect milk volume or increase it 3) small doses of hormones used for contraception do not appear to prevent initiation of lactation and 4) minute amounts of hormones are transmitted to the infant in breast milk and although no serious effects have been observed the long-term effects are unknown Determining the appropriate contraception during breastfeeding requires consideration of the womans personal preference availability and convenience of various methods impact on fertility of starting different methods at different times after delivery and possible effects on lactation Implications for family planning programs and research needs are also discussed

Fox G

Papers

Breast-feeding, fertility, and family planning.