Early-life mortality risks in opposite-sex and same-sex twins: a Danish cohort study of the twin testosterone transfer hypothesis

AbstractStudies on intraspecific contest behaviour predominantly focus on contests between individuals of the same sex, however contest behaviour is also expected to occur between individuals of the opposite sex including possible mates. Here we investigate potential trade-offs between mating and fighting behaviour in the turnip sawfly (Athalia rosae). Adults of this species collect chemical defence compounds (clerodanoids) directly from plants but also indirectly by nibbling on conspecifics that have already obtained clerodanoids themselves, a highly aggressive behavioural interaction. An A. rosae individual without clerodanoids may therefore be the potential mate or attacker of an individual of the opposite sex that has gained clerodanoids. We paired males and females with or without clerodanoid access and manipulated body mass differences between the sexes via the early life starvation of females. We show that asymmetrical clerodanoid acquisition between male-female pairs causes an increase in agonistic nibbling behaviour, irrespective of sex. Moreover, fighting over clerodanoids disrupted mating behaviour, and the frequency of aggressive nibbling behaviour in these pairs was determined by the comparative body mass of the attacking individual. Our study highlights the vital importance of investigating agonistic intersex interactions not only over mating but also over resources.

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The relationship between interpregnancy interval (IP) and mother's preceding pregnancies

10.1101/022111 ◽

2015 ◽

Author(s):

Michel C Vernier ◽

Michael Schulzer ◽

Pierre Vernier

Keyword(s):

Fetal Development ◽

Early Life ◽

Positive Association ◽

Negative Association ◽

Interval Length ◽

Gestation Length ◽

Interpregnancy Interval ◽

Same Sex ◽

Opposite Sex ◽

The Relationship

Introduction. Following the investigation of the mother's preceding pregnancies on fetal development and postnatal survival of the neonate, we turned our attention to an earlier period, that is the interval separating the onset of the current pregnancy from the end of the preceding one. The objectives of this study is to investigate the variations of interpregnancy interval length associated to the mother's preceding pregnancies. Methods. A population of 7773 neonates, alive at the time of hospital discharge, were divided into cohorts according to the current neonate's sex and number and sex of the mother's preceding pregnancies. Interpregnancy interval average of each cohort of same neonate's sex and mother's parity, but different configuration of preceding pregnancies, were measured and compared. Results. A positive association was found between mother's preceding pregnancies and length of interpregnancy interval when current pregnancy and preceding pregnancy were of the same sex, and a negative association when they were of opposite sex. Discussion. Interpregnancy interval length follows a pattern regarding the gravida's preceding pregnancy similar to the other early life indicators pattern, birth weight, placenta weight, gestation length and neonatal survival. Our results confirm and complete an immunological explanation of the indicators variations associated to the gravida's preceding pregnancy.

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Suicide among persons who entered same-sex and opposite-sex marriage in Denmark and Sweden, 1989–2016: a binational, register-based cohort study

Journal of Epidemiology & Community Health ◽

10.1136/jech-2019-213009 ◽

2019 ◽

Vol 74 (1) ◽

pp. 78-83 ◽

Cited By ~ 1

Author(s):

Annette Erlangsen ◽

Sven Drefahl ◽

Ann Haas ◽

Charlotte Bjorkenstam ◽

Merete Nordentoft ◽

...

Keyword(s):

Cohort Study ◽

Sexual Minority ◽

Minority Groups ◽

Age Groups ◽

Suicide Mortality ◽

Same Sex ◽

Suicide Rates ◽

Opposite Sex ◽

Males And Females ◽

Rate Ratios

BackgroundPeople belonging to sexual minority groups have higher levels of suicidality than heterosexuals. However, findings regarding suicide death are sparse. Using unique national data from two countries, we investigated whether individuals entering a same-sex marriage (SSM), a proxy group of sexual minority individuals, had higher suicide rates than those entering opposite-sex marriage (OSM).MethodsA cohort study of all males and females who entered an SSM (n=28 649) or OSM (n=3 918 617) in Denmark and Sweden during 1989–2016 was conducted. Incidence rate ratios (IRRs) for suicide were calculated using adjusted Poisson regression models.ResultsIn total, 97 suicides occurred among individuals who had entered an SSM compared with 6074 among those who entered an OSM, corresponding to an adjusted IRR of 2.3 (95% CI 1.9 to 2.8). For people who entered SSM, a 46% decline was noted over time from an IRR of 2.8 (95% CI 1.9 to 4.0) during 1989–2002 to 1.5 (95% CI 1.2 to 1.9) during 2003–2016. The excess suicide mortality was present in all age groups but most pronounced among younger individuals aged 18–34 years of age (IRR 2.7, 95% CI 1.5 to 4.8) and females (IRR 2.7, 95% CI 1.8 to 3.9).ConclusionThis large register-based study found higher suicide rates among individuals who entered an SSM, compared with those who entered an OSM. A lower suicide rate was noted for individuals in SSMs in recent years. More research is needed to identify the unique suicide risk and protective factors for sexual minority people.

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