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Ahrenfeldt LJ, Larsen LA, Lindahl-Jacobsen R, Skytthe A, Hjelmborg JVB, Möller S, Christensen K. Early-life mortality risks in opposite-sex and same-sex twins: a Danish cohort study of the twin testosterone transfer hypothesis. Ann Epidemiol 2016; 27:115-120.e2. [PMID: 28024904 DOI: 10.1016/j.annepidem.2016.11.011] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/31/2016] [Revised: 09/28/2016] [Accepted: 11/30/2016] [Indexed: 12/21/2022]
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.
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Affiliation(s)
- Linda Juel Ahrenfeldt
- Department of Public Health, The Danish Twin Registry, Unit of Epidemiology, Biostatistics and Biodemography, University of Southern Denmark, Odense C, Denmark; Department of Public Health, Max-Planck Odense Center on the Biodemography of Aging, University of Southern Denmark, Odense C, Denmark.
| | - Lisbeth Aagaard Larsen
- Department of Public Health, The Danish Twin Registry, Unit of Epidemiology, Biostatistics and Biodemography, University of Southern Denmark, Odense C, Denmark
| | - Rune Lindahl-Jacobsen
- Department of Public Health, The Danish Twin Registry, Unit of Epidemiology, Biostatistics and Biodemography, University of Southern Denmark, Odense C, Denmark; Department of Public Health, Max-Planck Odense Center on the Biodemography of Aging, University of Southern Denmark, Odense C, Denmark
| | - Axel Skytthe
- Department of Public Health, The Danish Twin Registry, Unit of Epidemiology, Biostatistics and Biodemography, University of Southern Denmark, Odense C, Denmark
| | - Jacob V B Hjelmborg
- Department of Public Health, The Danish Twin Registry, Unit of Epidemiology, Biostatistics and Biodemography, University of Southern Denmark, Odense C, Denmark
| | - Sören Möller
- Department of Public Health, The Danish Twin Registry, Unit of Epidemiology, Biostatistics and Biodemography, University of Southern Denmark, Odense C, Denmark
| | - Kaare Christensen
- Department of Public Health, The Danish Twin Registry, Unit of Epidemiology, Biostatistics and Biodemography, University of Southern Denmark, Odense C, Denmark; Department of Clinical Biochemistry and Pharmacology, Odense University Hospital, Odense C, Denmark; Department of Clinical Genetics, Odense University Hospital, Odense C, Denmark
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Abstract
OBJECTIVE To examine trends in twin gestational age over time, with adjustment for potential confounding factors, and to assess twin pair mortality and respiratory support over time. METHODS Rates of preterm births, respiratory support, and neonatal mortality were calculated for 21,569 twin pairs born from 1980 to 2005 in Washington State, using birth certificate and hospital discharge data. Fetal death risks were determined on a "per-pair-at-risk" basis. RESULTS While the proportion of twins born at 24-31 weeks remained stable at 8%, the proportion born at 32-36 weeks increased from 28% to 48%, and the proportion at 37-42 weeks declined from 64% to 44% (P<0.0001). Controlling individually for a variety of factors, such as maternal age, race, parity, and mode of delivery did not diminish the highly significant trend of increasing preterm births (P<0.0001 for each). Twin pair neonatal mortality decreased significantly through time (P<0.0001); however, the rate of pairs with one or both infants requiring oxygen or ventilation increased significantly through time (P<0.0001). Fetal death risks declined for term twins. CONCLUSIONS The proportion of twins born at 32-36 weeks' gestation has increased over time, along with requirement for respiratory support. Twin pair mortality decreased from 1980 to 2005.
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