STUDIES IN FETAL AND INFANT MORTALITY. II. DIFFERENTIALS IN MORTALITY BY SEX AND RACE

Does higher early neonatal mortality in boys reverse over the neonatal period? A pooled analysis from three trials of Nepal

OBJECTIVES

Neonatal mortality is generally 20% higher in boys than girls due to biological phenomena. Only a few studies have examined more finely categorised age patterns of neonatal mortality by sex, especially in the first few days of life. The objective of this study is to examine sex differentials in neonatal mortality by detailed ages in a low-income setting.

DESIGN

This is a secondary observational analysis of data.

SETTING

Rural Sarlahi district, Nepal.

PARTICIPANTS

Neonates born between 1999 and 2017 in three randomised controlled trials.

OUTCOME MEASURES

We calculated study-specific and pooled mortality rates for boys and girls by ages (0-1, 1-3, 3-7, 7-14, 14-21 and 21-28 days) and estimated HR using Cox proportional hazards models for male versus female mortality for treatment and control groups together (n=59 729).

RESULTS

Neonatal mortality was higher in boys than girls in individual studies: 44.2 vs 39.7 in boys and girls in 1999-2000; 30.0 vs 29.6 in 2002-2006; 33.4 vs 29.4 in 2010-2017; and 33.0 vs 30.2 in the pooled data analysis. Pooled data found that early neonatal mortality (HR=1.17; 95% CI: 1.06 to 1.30) was significantly higher in boys than girls. All individual datasets showed a reversal in mortality by sex after the third week of life. In the fourth week, a reversal was observed, with mortality in girls 2.43 times higher than boys (HR=0.41; 95% CI: 0.31 to 0.79).

CONCLUSIONS

Boys had higher mortality in the first week followed by no sex difference in weeks 2 and 3 and a reversal in risk in week 4, with girls dying at more than twice the rate of boys. This may be a result of gender discrimination and social norms in this setting. Interventions to reduce gender discrimination at the household level may reduce female neonatal mortality.

TRIAL REGISTRATION NUMBER

NCT00115271, NCT00109616, NCT01177111.

A biological approach to adult sex differences in skeletal indicators of childhood stress

OBJECTIVES

In previous work examining the etiology of cribra orbitalia (CO) and porotic hyperostosis (PH) in a contemporary juvenile mortality sample, we noted that males had higher odds of having CO lesions than females. Here, we examine potential reasons for this pattern in greater detail. Four non-mutually exclusive mechanisms could explain the observed sex differences: (1) sex-biased mortality; (2) sexual dimorphism in immune responses; (3) sexual dimorphism in bone turnover; or (4) sexual dimorphism in marrow conversion.

SUBJECTS AND METHODS

The sample consists of postmortem computed tomography scans and autopsy reports, field reports, and limited medical records of 488 individuals from New Mexico (203 females; 285 males) aged between 0.5 and 15 years. We used Kaplan-Meier survival analysis, predicted probabilities, and odds ratios to test each mechanism.

RESULTS

Males do not have lower survival probabilities than females, and we find no indications of sex differences in immune response. Overall, males have a higher probability of having CO or PH lesions than females.

CONCLUSIONS

All results indicate that lesion formation in juveniles is influenced by some combination of sex differences in the pace of red-yellow conversion of the bone marrow and bone turnover. The preponderance of males with CO and PH likely speaks to the potential for heightened osteoblastic activity in males. We find no support for the hypotheses that sex biases in mortality or immune responses impacted lesion frequency in this sample. Sex differences in biological processes experienced by children may affect lesion formation and lesion expression in later life.

A scoping review of methods for assessment of sex differentials in early childhood mortality

BACKGROUND

While assessment of sex differentials in child mortality is straightforward, their interpretation must consider that, in the absence of gender bias, boys are more likely to die than girls. The expected differences are also influenced by levels and causes of death. However, there is no standard approach for determining expected sex differences.

METHODS

We performed a scoping review of studies on sex differentials in under-five mortality, using PubMed, Web of Science, and Scopus databases. Publication characteristics were described, and studies were grouped according to their methodology.

RESULTS

From the 17,693 references initially retrieved we included 154 studies published since 1929. Indian, Bangladeshi, and Chinese populations were the focus of 44% of the works, and most studies addressed infant mortality. Fourteen publications were classified as reference studies, as these aimed to estimate expected sex differentials based upon the demographic experience of selected populations, either considered as gender-neutral or not. These studies used a variety of methods - from simple averages to sophisticated modeling - to define values against which observed estimates could be compared. The 21 comparative studies mostly used life tables from European populations as standard for expected values, but also relied on groups without assuming those values as expected, otherwise, just as comparison parameters. The remaining 119 studies were categorized as narrative and did not use reference values, being limited to reporting observed sex-specific estimates or used a variety of statistical models, and in general, did not account for mortality levels.

CONCLUSION

Studies aimed at identifying sex differentials in child mortality should consider overall mortality levels, and report on more than one age group. The comparison of results with one or more reference values, and the use of statistical testing, are strongly recommended. Time trends analyses will help understand changes in population characteristics and interpret findings from a historical perspective.

Maternal metabolic adaptations are necessary for normal offspring growth and brain development

Several metabolic adaptations emerge during pregnancy and continue through lactation, including increases in food intake and body weight, as well as insulin and leptin resistance. These maternal adaptations are thought to play a role in offspring viability and success. Using a model of attenuated maternal metabolic adaptations induced by ablation of the Socs3 gene in leptin receptor expressing cells (SOCS3 KO mice), our study aimed to investigate whether maternal metabolic changes are required for normal offspring development, and if their absence causes metabolic imbalances in adulthood. The litters were subjected to a cross‐fostering experimental design to distinguish the prenatal and postnatal effects caused by maternal metabolic adaptations. Males either born or raised by SOCS3 KO mice showed reduced body weight until 8 weeks of life. Both adult males and females born or raised by SOCS3 KO mice also had lower body adiposity. Despite that, no significant changes in energy expenditure, glucose tolerance or insulin resistance were observed. However, males either born or raised by SOCS3 KO mice showed reduced brain mass in adulthood. Furthermore, animals born from SOCS3 KO mice also had lower proopiomelanocortin fiber density in the paraventricular nucleus of the hypothalamus. In conclusion, these findings indicate that the commonly observed metabolic changes in pregnancy and lactation are necessary for normal offspring growth and brain development.

Sex differences in morbidity and care-seeking during the neonatal period in rural southern Nepal

BACKGROUND

South Asian studies, including those from Nepal, have documented increased risk of neonatal mortality among girls, despite their early biologic survival advantage. We examined sex differences in neonatal morbidity and care-seeking behavior to determine whether such differences could help explain previously observed excess late neonatal mortality among girls in Nepal.

METHODS

A secondary analysis of data from a trial of chlorhexidine use among neonates in rural Nepal was conducted. The objective was to examine sex differences in neonatal morbidity and care-seeking behavior for ill newborns. Girls were used as the reference group.

RESULTS

Referral for care was higher during the early neonatal period (ENP: 0-7 days old) (50.7%) than the late neonatal period (LNP: 8-28 days old) (31.3%), but was comparable by sex. There were some significant differences in reasons for referral by sex. Boys were significantly more often referred for convulsions/stiffness, having yellow body/eyes, severe skin infection, and having at least two of the following: difficulty breathing, difficulty feeding, fever, or vomiting during the ENP. Girls were more often referred for hypothermia. During the LNP, boys were significantly more often referred for having yellow body/eyes, persistent watery stool, and severe skin infection. There were no referral types in the LNP for which girls were more often referred. Less than half of those referred at any point were taken for care (47.0%) and referred boys were more often taken than girls (Neonatal Period OR: 1.77, 95% CI: 1.64 - 1.91). Family composition differentially impacted the relationship between care-seeking and sex. The greatest differences were in families with only prior living girls (Pahadi - ENP OR: 1.78, 95% CI: 1.29 - 2.45 and LNP OR: 1.51, 95% CI: 1.03 - 2.21; Madeshi - ENP OR: 2.86, 95% CI: 2.28 - 3.59 and LNP OR: 2.45, 95% CI: 1.84 - 3.26).

CONCLUSIONS

Care-seeking was inadequate for both sexes, but ill boys were consistently more often taken for care than girls, despite comparable referral. Behavioral interventions to improve care-seeking, especially in the early neonatal period, are needed to improve neonatal survival. Addressing gender bias in care-seeking, explicitly and within interventions, is essential to reducing neonatal mortality differentials between boys and girls.

Estimates of possible severe bacterial infection in neonates in sub-Saharan Africa, south Asia, and Latin America for 2012: a systematic review and meta-analysis

BACKGROUND

Bacterial infections are a leading cause of the 2·9 million annual neonatal deaths. Treatment is usually based on clinical diagnosis of possible severe bacterial infection (pSBI). To guide programme planning, we have undertaken the first estimates of neonatal pSBI, by sex and by region, for sub-Saharan Africa, south Asia, and Latin America.

METHODS

We included data for pSBI incidence in neonates of 32 weeks' gestation or more (or birthweight ≥1500 g) with livebirth denominator data, undertaking a systematic review and forming an investigator group to obtain unpublished data. We calculated pooled risk estimates for neonatal pSBI and case fatality risk, by sex and by region. We then applied these risk estimates to estimates of livebirths in sub-Saharan Africa, south Asia, and Latin America to estimate cases and associated deaths in 2012.

FINDINGS

We included data from 22 studies, for 259 944 neonates and 20 196 pSBI cases, with most of the data (18 of the 22 studies) coming from the investigator group. The pooled estimate of pSBI incidence risk was 7·6% (95% CI 6·1-9·2%) and the case-fatality risk associated with pSBI was 9·8% (7·4-12·2). We estimated that in 2012 there were 6·9 million cases (uncertainty range 5·5 million-8·3 million) of pSBI in neonates needing treatment: 3·5 million (2·8 million-4·2 million) in south Asia, 2·6 million (2·1 million-3·1 million) in sub-Saharan Africa, and 0·8 million (0·7 million-1·0 million) in Latin America. The risk of pSBI was greater in boys (risk ratio 1·12, 95% CI 1·06-1·18) than girls. We estimated that there were 0·68 million (0·46 million-0·92 million) neonatal deaths associated with pSBI in 2012.

INTERPRETATION

The need-to-treat population for pSBI in these three regions is high, with ten cases of pSBI diagnosed for each associated neonatal death. Deaths and disability can be reduced through improved prevention, detection, and case management.

FUNDING

The Wellcome Trust and the Bill & Melinda Gates Foundation through grants to Child Health Epidemiology Reference Group (CHERG) and Save the Children's Saving Newborn Lives programme.

Sex differences in neonatal mortality in Sarlahi, Nepal: the role of biology and environment

BACKGROUND

Studies in South Asia have documented increased risk of neonatal mortality among girls, despite evidence of a biological survival advantage. Associations between gender preference and mortality are cited as reasons for excess mortality among girls. This has not, however, been tested in statistical models.

METHODS

A secondary analysis of data from a population-based randomised controlled trial of newborn infection prevention conducted in rural southern Nepal was used to estimate sex differences in early and late neonatal mortality, with girls as the reference group. The analysis investigated which underlying biological factors (immutable factors specific to the newborn or his/her mother) and environmental factors (mutable external factors) might explain observed sex differences in mortality.

RESULTS

Neonatal mortality was comparable by sex (Ref=girls; OR 1.06, 95% CI 0.92 to 1.22). When stratified by neonatal period, boys were at 20% (OR 1.20, 95% CI 1.02% to 1.42%) greater risk of early and girls at 43% (OR 0.70, 95% CI 0.51% to 0.94%) greater risk of late neonatal mortality. Biological factors, primarily respiratory depression and unconsciousness at birth, explained excess early neonatal mortality among boys. Increased late neonatal mortality among girls was explained by a three-way environmental interaction between ethnicity, sex and prior sibling composition (categorised as primiparous newborns, infants born to families with prior living boys or boys and girls, and infants born to families with only prior living girls).

CONCLUSIONS

Risk of neonatal mortality inverted between the early and late neonatal periods. Excess risk of early neonatal death among boys was consistent with biological expectations. Excess risk for late neonatal death among girls was not explained by overarching gender preference or preferential care-seeking for boys as hypothesised, but was driven by increased risk among Madeshi girls born to families with only prior girls.

Neonatal, postneonatal, childhood, and under-5 mortality for 187 countries, 1970-2010: a systematic analysis of progress towards Millennium Development Goal 4

BACKGROUND

Previous assessments have highlighted that less than a quarter of countries are on track to achieve Millennium Development Goal 4 (MDG 4), which calls for a two-thirds reduction in mortality in children younger than 5 years between 1990 and 2015. In view of policy initiatives and investments made since 2000, it is important to see if there is acceleration towards the MDG 4 target. We assessed levels and trends in child mortality for 187 countries from 1970 to 2010.

METHODS

We compiled a database of 16 174 measurements of mortality in children younger than 5 years for 187 countries from 1970 to 2009, by use of data from all available sources, including vital registration systems, summary birth histories in censuses and surveys, and complete birth histories. We used Gaussian process regression to generate estimates of the probability of death between birth and age 5 years. This is the first study that uses Gaussian process regression to estimate child mortality, and this technique has better out-of-sample predictive validity than do previous methods and captures uncertainty caused by sampling and non-sampling error across data types. Neonatal, postneonatal, and childhood mortality was estimated from mortality in children younger than 5 years by use of the 1760 measurements from vital registration systems and complete birth histories that contained specific information about neonatal and postneonatal mortality.

FINDINGS

Worldwide mortality in children younger than 5 years has dropped from 11.9 million deaths in 1990 to 7.7 million deaths in 2010, consisting of 3.1 million neonatal deaths, 2.3 million postneonatal deaths, and 2.3 million childhood deaths (deaths in children aged 1-4 years). 33.0% of deaths in children younger than 5 years occur in south Asia and 49.6% occur in sub-Saharan Africa, with less than 1% of deaths occurring in high-income countries. Across 21 regions of the world, rates of neonatal, postneonatal, and childhood mortality are declining. The global decline from 1990 to 2010 is 2.1% per year for neonatal mortality, 2.3% for postneonatal mortality, and 2.2% for childhood mortality. In 13 regions of the world, including all regions in sub-Saharan Africa, there is evidence of accelerating declines from 2000 to 2010 compared with 1990 to 2000. Within sub-Saharan Africa, rates of decline have increased by more than 1% in Angola, Botswana, Cameroon, Congo, Democratic Republic of the Congo, Kenya, Lesotho, Liberia, Rwanda, Senegal, Sierra Leone, Swaziland, and The Gambia.

INTERPRETATION

Robust measurement of mortality in children younger than 5 years shows that accelerating declines are occurring in several low-income countries. These positive developments deserve attention and might need enhanced policy attention and resources.

FUNDING

Bill & Melinda Gates Foundation.

The rise and fall of excess male infant mortality

The male disadvantage in infant mortality underwent a surprising rise and fall in the 20th century. Our analysis of 15 developed countries shows that, as infant mortality declined over two centuries, the excess male mortality increased from 10% in 1751 to >30% by approximately 1970. Remarkably, since 1970, the male disadvantage in most countries fell back to lower levels. The worsening male disadvantage from 1751 until 1970 may be due to differential changes in cause-specific infant mortality by sex. Declines in infant mortality from infections and the shift of deaths to perinatal conditions favored females. The reduction in male excess infant mortality after 1970 can be attributed to improved obstetric practices and neonatal care. The additional male infants who survived because of better conditions were more likely to be premature or have low birth weight, which could have implications for their health in later life. This analysis provides evidence of marked changes in the sex ratio of mortality at an age when behavioral differences should be minimal.

Narrowing of sex differences in infant mortality in Massachusetts

OBJECTIVES

To examine whether the improved survival of preterm infants has influenced the known male excess in infant mortality.

STUDY DESIGN

We analyzed sex-specific infant mortality using linked birth and death certificates for all 619,811 live born infants in Massachusetts between 1989 and 1995.

RESULTS

Between 1989 and 1995 the male excess in infant mortality decreased by 50%, from 1.6/1000 to 0.8/1000 live births (LB). This narrowing resulted primarily from a more rapid decline in neonatal mortality among male infants (1.5/1000 LB) than among female infants (0.9/1000 LB). The largest declines in the male excess in neonatal mortality occurred among very premature infants (GA < or = 30 weeks) and resulted primarily from a more rapid decrease in male deaths from respiratory distress syndrome.

CONCLUSIONS

The narrowing of the sex difference in mortality between 1989 and 1995 suggests that newer treatments like antenatal steroids, and surfactants may have differentially benefited male infants.

Natural selection and sex differences in morbidity and mortality in early life

Both morbidity and mortality are consistently reported to be higher in males than in females in early life, but no explanation for these findings has been offered. This paper argues that the sex difference in early vulnerability can be attributed to the natural selection of optimal maternal strategies for maximizing lifetime reproductive success, as modelled previously by Trivers and Willard. These authors theorized that males and females offer different returns on parental investment depending on the state of the environment. Natural selection has therefore favoured maternal ability to manipulate offspring sex in response to environmental conditions in early life, as shown in variation in the sex ratio at birth. This argument can be extended to the whole period of parental investment until weaning. Male vulnerability in response to environmental stress in early life is predicted to have been favoured by natural selection. This vulnerability is most evident in the harsh conditions resulting from pre-term birth, but can also be seen in term infants, and manifests as greater morbidity and mortality persisting into early childhood. Malnutrition, interacting with infection after birth, is suggested as the fundamental trigger mechanism. The model suggests that whatever improvements are made in medical care, any environmental stress will always affect males more severely than females in early life.

A multicentre study of perinatal mortality in Nepal

A prospective survey was carried out in two Kathmandu hospitals and two rural districts to establish urban and rural perinatal mortality rates (PNMRs) for these four centres in Nepal and to ascertain the causes of perinatal mortality. All perinatal deaths occurring over a 1-year period in the four centres were included (during which time there was a total of 14,967 births). Cause of death was established by contemporary review of hospital case records or by structured questionnaire ('verbal autopsy') in the rural areas. The PNMRs in the hospitals were 48.0 and 23.7 per thousand total births respectively, whilst those of the rural settings were 96.2 and 42.5 per thousand births. Perinatal asphyxia, low birthweight and infection were the most common causes but many of the deaths were unexplained. The high mortality rates were felt to reflect the difficult circumstances of childbirth in Nepal. It was concluded that a number of interventions would appear appropriate, but that these should be introduced in a scientific manner.

Morbidity in early childhood: differences between girls and boys under 10 years old

The aim of the study was to investigate the differences in presented morbidity and use of health services among boys and girls in early childhood. The study was performed using data collected by the continuous morbidity registration project of the department of general practice at Nijmegen University. All recorded morbidity, referrals to specialists and admissions to hospitals were recorded by the registration project. The study population included children born in four practices from 1971 to 1984. The children were followed up until the age of five years and if possible until the age of 10 years. The morbidity of the children had been categorized into three levels of seriousness of diagnosis and 15 diagnostic groups as part of the registration project. Boys presented more morbidity than girls in the first years of their lives. For the age group 0-4 years this was true for all levels of seriousness of diagnosis except the most serious. In this younger age group significantly more boys than girls suffered respiratory diseases, behaviour disorders, gastroenteritis and accidents. Girls suffered from more episodes of urinary infection than boys in both age groups. More boys were referred to specialists and admitted to hospital than girls. The findings of this study suggest that not only inborn factors can explain the sex differences in presented morbidity and use of health services in early childhood. In particular, differences between girls and boys in terms of non-serious morbidity and referral and admission rates suggest a different way of handling health problems in boys and girls in early childhood both by parents and doctors.(ABSTRACT TRUNCATED AT 250 WORDS)

Factors affecting the sex differential in neonatal mortality: the role of respiratory distress syndrome

We investigated factors affecting the sex differential in neonatal mortality rate using linked birth and death certificates of more than 300,000 infants born in Georgia between 1974 and 1977. The neonatal mortality rate was higher in male infants than in female infants (relative risk = 1.23, p less than 10(-8)) and was most pronounced for infants weighing between 1501 and 2500 gm (relative risk = 1.78, p less than 10(-8)). This differential persisted after adjustment was made for effects of several prenatal and labor-related factors. The male excess in neonatal mortality rate was most prominent during the first week of life and was found for several perinatal disorders. Respiratory distress syndrome-related mortality showed the largest male excess (relative risk = 1.57, p less than 10(-8)) and was most pronounced in infants weighing between 1501 and 2500 gm (relative risk = 2.78, p less than 10(-8)), in whom it accounted for roughly 60% of the excess. Since previous studies have shown that male infants have a higher incidence of respiratory distress syndrome but not a higher case-fatality rate, we suggest that slower lung maturation among male fetuses is a major contributing factor to the sex differential in neonatal mortality.

Sex differences in human mortality: the role of genetic factors

This paper reviews evidence concerning genetic factors that influence sex differences in human mortality, with attention to the interactions between genetic and environmental factors. Some widely quoted earlier conclusions, for example, that males have consistently higher fetal mortality than females, are not supported by current evidence. For example, for late fetal mortality, males had higher rates than females in earlier historical data, but not in recent data for several advanced industrial countries. This reflects a changing balance between an inherently greater female vulnerability for one major type of late fetal mortality and inherently greater male vulnerability for several other types of late fetal mortality that have declined in importance as health care has improved. Males appear to be inherently more vulnerable than females to infant mortality, although the causes of this vulnerability are poorly understood. X-linked immunoregulatory genes appear to contribute to greater female resistance to infectious diseases. Despite these apparent inherent advantages for females, in some situations females have had higher infant mortality and higher infectious disease mortality than males, apparently due to environmental disadvantages for females, such as less adequate diet and health care. Inherent sex differences in reproductive physiology and anatomy contribute to higher female mortality for breast cancer and maternal mortality. For these causes of death, as for the other categories discussed, the death rates and thus the contributions to sex differences in total mortality vary considerably depending on environmental conditions. Several hypothesized contributions of sex hormones to sex differences in mortality are at present controversial due to contradictions and limitations in the available data. There may be effects of male sex hormones on sex differences in behavior which contribute to males' higher death rates for accidents and other violent causes. Women's endogenous sex hormones may reduce women's risk of ischemic heart disease. For both violent deaths and ischemic heart disease it appears that any genetic contributions to sex differences in mortality are strongly reinforced by the cultural influences that foster more risky behavior in males, including more use of weapons, employment in hazardous occupations, heavy alcohol consumption and cigarette smoking. It appears that these cultural influences on sex differences in behavior are widespread cross-culturally in part because of the effects of inherent sex differences in reproductive functions on the cultural evolution of sex roles. These examples illustrate the complexity and importance of interactions between genetic and environmental factors in determining sex differences in human mortality.

Causes of perinatal mortality in an African city

Little has been published about the causes of most of the deaths responsible for the high perinatal mortality rates characteristic of preindustrial, urban societies. The present study searched for answers in one such society by identifying the causes of death in a large-scale analysis of perinatal mortality in Addis Ababa, Ethiopia. A 72% autopsy rate was achieved when 1019 postmortem examinations were performed for 1424 consecutive perinatal deaths. The overall perinatal mortality rate was 65.3 per thousand live births. The ratio of stillbirths to neonatal deaths was 2.7:1, indicating that maternal factors were dominant in causing the deaths. One-third of the deaths were due to amniotic fluid infections, 15% to obstructed labour, 8% to abruptio placentae, and the rest to more than 20 other specific disorders.

Why do women live longer than men?

In the contemporary United States, males have 60 percent higher mortality than females. In Part I, published in the previous issue, we showed that 40 percent of this sex differential in mortality is due to a twofold elevation of arteriosclerotic heart disease among men. Major causes of higher rates of arteriosclerotic heart disease in men include greater cigarette smoking among men; probably a greater prevalence of the competitive, aggressive Coronary Prone Behavior Pattern among men; and possibly a protective role of female hormones. In addition, men have higher death rates for lung cancer and emphysema, primarily because more men smoke cigarettes. In Part II we analyze the other major causes of men's higher death rates: accidents, suicide, and cirrhosis of the liver. Each of these is related to behaviors which are encouraged or accepted more in men than in women in our society--for example, using guns, being adventurous and acting unafraid, working at hazardous jobs and drinking alcohol. We conclude with suggestions for reducing male mortality; for example, by changing the social conditions which foster in men the behaviors that elevate their mortality.

Why do women liver longer than men?

In the contemporary United States, mortality is 60% higher for males than for females. Forty percent of the excess of male mortality is due to arteriosclerotic heart disease, which is more common among men in part because they smoke cigarettes more than women do, and apparently also because they more often develop the competitive, aggressive Coronary Prone Behavior Pattern. Men who do not develop this Behavior Pattern may have as low a risk of coronary heart disease as comparable women. Oophorectomy of young women may increase the risk of coronary heart disease, but administration of female hormones generally does not reduce risk. One third of the sex differential in mortality is due to men's higher rates of suicide, fatal motor vehicle and other accidents, cirrhosis of the liver, respiratory cancers and emphysema. Each of these causes of death is linked to behaviours which are encouraged or accepted more in males than in females: using guns, drinking alcohol, smoking, working at hazardous jobs, and seeming to be fearless. Thus, the behaviors expected of males in our society make a major contribution to their elevated mortality.