A group of researchers from the Institute for Women’s Health, University College London, UK, published a study in the BMJ Open journal, titled “Association of skirt size and postmenopausal breast cancer risk in older women: a cohort study within the UK Collaborative Trial of Ovarian Cancer Screening (UKCTOCS)”, where they found that going up one skirt size every 10 years was associated with a 33% greater risk of developing breast cancer in postmenopausal women.

Different studies have suggested that obesity is associated with an increased risk in breast cancer development in postmenopausal women. However, no studies had investigated the link between central obesity and breast cancer.

With this in mind, researchers decided to analyze almost 93,000 women that had enrolled in the UK Collaborative Trial of Ovarian Cancer Screening (UKCTOCS) in England, to report on the association of breast cancer risk with self-reported skirt size (SS; waist-circumference proxy) changes between 20 years of age and postmenopausal-age.

All women participating in the study were over 50 years of age, had gone through menopause, had no known breast cancer, and reported specific information considered to influence breast cancer risk, such as height and weight (BMI), reproductive health, fertility, family history of breast and ovarian cancer, use of hormonal contraceptives, and hormonal replacement therapy.

Throughout the study, 1,090 women developed breast cancer, a risk that was tightly associated with infertility treatment, family history of breast/ovarian cancer, and use of hormonal replacement therapy.

Nonetheless, the authors observed that an increase in skirt size was one of the strongest predictors of breast cancer risk.

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Results showed that at the age of 25, average skirt size was a US 8, and upon enrollment in the study at an average age of 64, it was a US 10.

Increasing one and two skirt sizes every 10 years was associated with a 33% and 77% greater risk of developing breast cancer after menopause, respectively.

Moreover, the five-year absolute risk of postmenopausal breast cancer rised from 1 in 61 to 1 in 51 with each increase in skirt size every 10 years.

Because this was an observational study, no definitive conclusions could be taken. However, other studies have already linked waistline size with other types of cancers, such as pancreas, lining of the womb and ovaries.

“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 authors write in their report, mentioning that an increase in fat can enhance the levels of oestrogen, a known key player in breast cancer development.