Women between the age of 20 to 50 who increase a standard skirt size over 10 years a 33% greater risk of developing breast cancer after the menopause, according to a UK study.
Going up two skirt sizes in the same period was associated with a 77% greater risk.
Overall weight gain during adulthood is known to be a risk factor for breast cancer but a thickening
waist seems to be particularly harmful.
The researchers base their findings on almost 93,000 women taking part in the UK Collaborative Trial
of Ovarian Cancer Screening in England.
The women were all aged over 50, had gone through the menopause, and had no known breast
cancer when they entered the study between 2005 and 2010.
But after taking account of other influential factors, increases in skirt size emerged as the strongest predictor of breast cancer risk.
At the age of 25, the average skirt size was a UK 12 (US 8; Europe 40-44) and when they entered the study at the average age of 64, it was a 14 (US 10; Europe 42-46).
Skirt size increased over the course of their adult lives in three out of four of the women.
The researchers estimate that the five year absolute risk of postmenopausal breast cancer rises from
1 in 61 to 1 in 51 with each increase in skirt size every 10 years.
“Although the exact mechanism of these relationships need to be better understood, there is a
suggestion that body fat around the waist is more metabolically active than adipose tissue elsewhere,” the researchers write.
Extra fat is known to boost levels of the female hormone oestrogen on which many breast cancer cells rely for fuel.
The results of the observational study are published in the online UK journal BMJ Open.
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