Resting energy expenditure confers breast cancer risk

High resting energy expenditure (REE) contributes to an increase in the risk of invasive breast cancer among postmenopausal women, as reported in a study.

Researchers looked at 137,283 postmenopausal women in the Women's Health Initiative (WHI) to examine the association between predicted REE (calculated using the Ikeda, Livingston, and Mifflin equations) and risk of postmenopausal breast cancer overall, by subtypes, and by level of body fat.

Over a median follow-up of 19 years, 9,396 women developed invasive breast cancer. These women were more likely to have lower educational level, a family history of breast cancer in a first-degree relative, an early age at menarche (<12 years), be nulliparous, and have a higher body mass index (BMI), waist circumference (WC), and predicted REEs.

In multivariable Cox proportional hazards models, the highest vs lowest quartile of all predicted REEs showed a positive association with the risk of invasive breast cancer (Ikeda: hazard ratio [HR], 1.69, 95 percent confidence interval [CI], 1.57–1.81; Livingston: HR, 1.69, 95 percent CI, 1.57–1.82; Mifflin: HR, 1.68, 95 percent CI, 1.56–1.80). These associations were independent of the hormone receptor subtype, grade, and stage of the tumours, but were most pronounced for oestrogen receptor–positive/progesterone receptor–positive tumours.

Following additional adjustment for BMI, the associations were mostly attenuated but remained statistically significant for most of the outcomes. Furthermore, there was an interaction detected between predicted REEs and BMI, with the associations being somewhat pronounced among normal weight and overweight women vs obese women (p_interactions<0.05).

The findings may help improve the understanding of the pathophysiology of breast cancer, as REE provides energy to support cancer-associated disorders such as obesity and inflammation.