Results from a study of nearly 100,000 women suggest that increasing skirt size over a lifetime--a proxy for waist circumference-may be an indicator of increased risk of postmenopausal breast cancer.
The results are based on evaluation of data from 92,834 participants in 9 trials centers in England as part of the UK Collaborative Trial of Ovarian Cancer Screening. All were postmenopausal women aged >50 years (median age 64) with no known history of breast cancer before study entry or on the day of completion of the study’s entrance questionnaire. The women were followed up via “flagging” at the National Health Service Information Centre and Hospital Episode Statistics.
Questionnaires were completed between January 2, 2005 and July 1, 2010 and median follow-up was 3.19 years (25th–75th centile: 2.46–3.78), Of the 92,834 participants, 1090 developed breast cancer. When adjusting for confounders, changing skirt size showed a stronger positive association than without adjustment, (hazard ratio [HR]=1.330 per 10â years; 95% confidence interval [CI] 1.121 to 1.579; p=0.001). Using adiposity measures other than change skirt size, body mass index (HR=1.076 per 5 units; 95% CI 1.018 to 1.136; p=0.009) and skirt size (HR=1.051; 95% CI 1.014 to 1.089; p=0.006) at study entry showed a lesser association with breast cancer risk.
Change in UK skirt size was the single most predictive measure of adiposity. Further analysis of change in skirt size and body mass index (BMI) showed that the changing skirt size remained significant (HR=1.266; 95% CI 1.041 to 1.538), while BMI did not (HR=1.037; 95% CI 0.970 to 1.109).
According to the investigators, their study is the only one of its kind to investigate the association between breast cancer risk and changing skirt size. They estimate that each unit increase in UK skirt size per 10 years between age 25 years and postmenopausal age leads to a 5-year absolute risk of postmenopausal breast cancer from 1 in 61 to 1 in 51, or a 33% increase in risk. Validation of their results, the authors said, could give women an easy-to-understand message about their health.
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