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Comparative Study
. 2017 Feb;27(2):115-120.e2.
doi: 10.1016/j.annepidem.2016.11.011. Epub 2016 Dec 9.

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

Linda Juel Ahrenfeldt  1 , Lisbeth Aagaard Larsen  2 , Rune Lindahl-Jacobsen  3 , Axel Skytthe  2 , Jacob V B Hjelmborg  2 , Sören Möller  2 , Kaare Christensen  4
Affiliations
Comparative Study

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

Linda Juel Ahrenfeldt et al. Ann Epidemiol. 2017 Feb.

Abstract

Purpose: To investigate the twin testosterone transfer (TTT) hypothesis by comparing early-life mortality risks of opposite-sex (OS) and same-sex (SS) twins during the first 15 years of life.

Methods: We performed a population-based cohort study to compare mortality in OS and SS twins. We included 68,629 live-born Danish twins from 1973 to 2009 identified through the Danish Twin Registry and performed piecewise stratified Cox regression and log-binomial regression.

Results: Among 1933 deaths, we found significantly higher mortality for twin boys than for twin girls. For both sexes, OS twins had lower mortality than SS twins; the difference persisted for the first year of life for boys and for the first week of life for girls.

Conclusions: Although the mortality risk for OS boys was in the expected direction according to the TTT hypothesis, the results for OS girls pointed in the opposite direction, providing no clear evidence for the TTT hypothesis.

Keywords: Mortality; Opposite-sex; Same-sex; Sex; Twins.

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Conflict of interest statement

The authors have no competing interests to declare.

Figures

Fig. 1
Fig. 1
Hazard ratios and 95% confidence intervals (CIs) for all-cause mortality 0–15 years stratified on age and decades for live-born opposite-sex and same-sex twins born in Denmark during 1973–2009.
Fig. 2
Fig. 2
Kaplan-Meier curves with 95% confidence bands for all-cause mortality 0–15 years for the last 4 decades for opposite-sex and same-sex live-born twin boys in Denmark during 1973–2009.
Fig. 3
Fig. 3
Kaplan-Meier curves with 95% confidence bands for all-cause mortality 0–15 years for the last 4 decades for opposite-sex and same-sex live-born twin girls in Denmark during 1973–2009.
See this image and copyright information in PMC

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