At some point in their adult lives, most women have found that a dress or pair of shorts that fit last summer is a bit too snug this season. According to new British research, more is at stake than vanity or wounded pride.

A study of almost 93,000 women found going up a skirt size (for example, from size 12 to size 14) every 10 years between the ages of 25 and 50 increased postmenopausal breast cancer risk by 33 percent. However, those women whose skirt size went down had a decreased risk of developing breast cancer.

Skirt size may give women a tangible way to understand the link between breast cancer risk and changes in waist size.

It is not that skirt size causes breast cancer, it's what it represents. There is a good deal of evidence showing that increases in body fat, as measured by body weight, weight gain in adulthood, and body mass index, are associated with an increase in breast cancer risk.

This is the first large trial to look at the association between breast cancer risk and increases in abdominal fat as represented by larger skirt size, and the researchers believe skirt size may give women a tangible way to understand the link between breast cancer risk and changes in waist size.

“This was something we observed in our ovarian cancer screening trial participants,” Usha Menon, corresponding author on the study, told TheDoctor via email. “We hope others working in the area of breast cancer will explore this issue further, for if confirmed, skirt size is a simple and easy measure to use.”

Study participants were 50 years old or older, with an average age of 64. They had no known history of breast cancer prior to enrolling in the study. At the start of the study, the women were asked about their skirt size in their 20s and their current skirt size, Menon, head of the gynecological cancer research center at University College, London, said.

The average skirt size of the women at age 25 was a U.K. size 12 or a U.S. size 8. By the time they enrolled in the study, their skirt size was a 14 (U.S. size 10). Skirt size increased throughout adulthood in three out of four women.

A number of factors may connect breast cancer risk and weight gain, Menon said. They include insulin resistance, chronic inflammation, and a change in sex hormone levels, particularly estrogens. “There is evidence,” the authors explain, “that adipose tissue (fat) around the waist is more metabolically active than adipose elsewhere.”

The study was published online recently in BMJ Open.