Table 4 -.
Studies on other health traits in opposite-sex and same-sex twins
| Trait | Publication | Setting | Numbers of opposite-sex (OS) and same-sex (SS) twins | Is there a comparison between OS and SS dizygotic (DZ) twins only?a | Age | Assessment | Findings OS vs. SS females | Findings OS vs. SS males | Suggests evidence for masculiniza-tion of OS femalesb | Suggests evidence for demasculiniza-tion of OS malesb |
|---|---|---|---|---|---|---|---|---|---|---|
| Cancer | Ahrenfeldt et al., 2015b | Denmark and Sweden | 44,650 OSF 84,721 SSF 44,660 OSM 88,261 SSM |
Yes – comparison between OS and SS (DZ)+UZ twins | 0–73 years Denmark: mean = 25 years at start of follow up Sweden: mean = 24 years at start of follow up |
All-cause cancer and sex-specific cancers identified from the Danish and Swedish twin and cancer registries | No significant differences | No significant differences | − | − |
| Early life mortality risks | Ahrenfeldt et al., 2017 | Denmark | 12,033 OSF 12,051 OSM 21,644 SSF 22,901 SSM |
No | 0–15 years | Perinatal mortality, neonatal and postneonatal deaths and child mortality identified through the Danish Twin Registry | OSF lower perinatal and early neonatal mortality than SSF | OSM lower perinatal, neonatal and postneonatal mortality than SSM - may be due to MZ twins in the SS twin group | − | +/− |
| Epilepsi | Mao et al., 2018 | Denmark | 11,078 OSF 19,186 SSF 11,080 OSM 20,207 SSM |
Yes | 0–34 years | Epilepsy identified through the Danish National Patient Registry | No significant differences | No significant differences | − | − |
NA: Not available, OS: opposite-sex, SS = same-sex, F = females, M = males, MZ = monozygotic, DZ = dizygotic, UZ = unknown zygosity
Yes: The study makes a separate comparison of OS vs SSDZ twins, although it includes both MZ and DZ twins.
No: The study does not make a separate comparison of OS vs SSDZ twins, thus, including MZ twins in all analyses.
DZ twins only: The study includes DZ twins only. Thus, no MZ twins are included in the study.
+: The study provides evidence for masculinization of OS females/demasculinization of OS males.
−: The study provides no evidence for masculinization of OS females/demasculinization of OS males.
+/−: The study provides evidence for masculinization of OS females/demasculinization of OS males in some cases (e.g. in some investigated measures, in some age groups or in some statistical analyses), but not in all.