Table 1.

Description of female twins from same-sexed pairs in the Nordic Twin Studies of Cancer (NorTwinCan) cohorts

DenmarkFinlandNorwaySwedenTotal
Birth cohorts1870–20041880–19571895–19791886–2008
Cancer registration since1943195319531958
Initiation of follow-up1943197519641961
End of follow-up2009–12-312010–12-312008–12-312009–12-31
N female twins33,33912,50712,82445,869104,539
N MZ/DZ complete pairs6,235/10,4302,026/4,1792,935/3,4399,859/12,89221,055/30,940
N MZ/DZ complete uncensored pairs1,251/2,332403/792195/2321,781/3,2383,630/6,594
N breast cancer cases1,2296353581,7113,933
N breast cancer in complete pairs1,2296303521,7003,911
N breast cancer in complete uncensored pairs695221919071,914
N concordant uncensored MZ/DZ pairs44/4815/2313/552/65124/141
N discordant uncensored MZ/DZ pairs170/34139/10618/37243/430470/914
N unaffected uncensored MZ/DZ pairs1,037/1,943349/663164/1901,486/2,7433,036/5,539