An increase in skirt size each decade among women aged between their mid-20s and mid-50s appeared to be associated with a 33% elevated risk for postmenopausal breast cancer, according to study results.
“There is a large body of evidence that high BMI is associated with increased breast cancer risk in postmenopausal women and reduced risk in premenopausal women,” Usha Menon, MD, and colleagues from the department of Women’s Cancer at the University College of London, wrote. “Another suggested breast cancer risk predictor is adult weight gain, which typically reflects an increase in body fat.”
In the prospective cohort study, researchers evaluated 92,834 women aged at least 50 years who were enrolled in the UK Collaborative Trial of Ovarian Cancer Screening (UKCTOCS) between 2005 and July 2010. UKCTOCS is a multicenter randomized controlled trial pertaining to ovarian cancer screening in the general public. All study participants completed a baseline questionnaire and follow-up questionnaire at 3 to 4 years after recruitment.
This follow-up questionnaire was used as the initial questionnaire for the current study, and none of the participants had a history of breast cancer at the time of this index questionnaire. The questionnaire asked questions related to education, skirt size, ongoing use of hormone therapy, smoking and health status.
The researchers followed the study participants through a “flagging study” with the Health and Social Care National Health Service (NHS) Information Centre, which provided updates on cancer registrations or deaths among the study cohort. The median follow-up was 3.19 years.
The researchers found that during the follow-up period, 1,090 women developed breast cancer. Consistent with previous studies, they found a significant association between increased breast cancer risk and family history of breast cancer, infertility, age at last menstruation and hormone therapy use.
After adjusting for potential confounders, they found that the following adiposity measures were associated with increased breast cancer risk: BMI at recruitment to UKCTOCS (HR for a 5-unit change=1.076; 95% CI, 1.012-1.135); current skirt size at study entry (HR=1.051; 95% CI, 1.014-1.089); and change in skirt size per 10 years (HR=1.33; 95% CI, 0.958-1.056).
Of the adiposity measured, change in skirt size was found to be the most significant predictor of breast cancer. Moreover, in a variation of the full model that included both skirt size and BMI, change in skirt size was found to have an independent association with breast cancer (HR= 1.266; 95% CI, 1.041-1.538) but BMI did not (HR=1.037; 95% CI, 0.97-1.109).
“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,” Menon and colleagues wrote. “Obesity is known to increase estrogen levels as a result of aromatization of androstenedione in adipose tissue as well as affect insulin resistance and chronic inflammation, well known factors shown to increase breast cancer risk.”
Disclosure: The researchers report no relevant financial disclosures.