MONDAY, June 25, 2018 (HealthDay News) -- Across body mass index (BMI) distribution, increased BMI is associated with reduced risk of premenopausal breast cancer, according to a study published online June 21 in JAMA Oncology.
Minouk J. Schoemaker, Ph.D., from The Institute of Cancer Research in London, and colleagues from the Premenopausal Breast Cancer Collaborative Group examined the correlation of BMI with premenopausal breast cancer risk in a multicenter analysis using pooled individual-level data from 758,592 premenopausal women from 19 prospective cohorts. Participants were followed for a median of 9.3 years per participant to estimate the hazard ratios of premenopausal breast cancer in association with BMI; there were 13,082 incident cases of breast cancer during follow-up.
The researchers found that inverse linear associations of BMI with breast cancer risk were identified that were stronger for BMI at ages 18 to 24 years than for BMI at ages 45 to 54 years (hazard ratios per 5 kg/m² difference, 0.77 and 0.88, respectively). Even among non-overweight women, these inverse associations were observed. At ages 18 to 24 years there was a 4.2-fold risk gradient between the highest and lowest BMI categories (BMI ≥35.0 vs <17.0 kg/m²: hazard ratio, 0.24). There was no appreciable variation in hazard ratios by attained age or between strata of other breast cancer risk factors.
"Increased adiposity is associated with a reduced risk of premenopausal breast cancer at a greater magnitude than previously shown and across the entire distribution of BMI," the authors write.