Adherence to a healthy Nordic food index and breast cancer risk: results from a Swedish cohort study

Background: A healthy Nordic dietary pattern has shown beneficial effects in relation to several chronic diseases. However, no study has evaluated the association between a healthy Nordic food index (HNFI) and risk of breast cancer. Methods: We conducted a prospective cohort study including 44,296 women, aged 29–49 at baseline in 1991–1992, who completed a food frequency questionnaire at baseline, and have been followed up ever since, through the Swedish Cancer Registry and Cause of Death Registry. Each woman was assigned a HNFI score ranging from 0 to 6. We calculated multivariable relative risks (RRs) and 95 % confidence intervals (CIs) using Poisson regression models with attained age as the underlying timescale. The association between the HNFI and risk of breast cancer was assessed both overall, by menopausal status and by hormone receptor status. Results: A total of 1,464 breast cancer cases were diagnosed during a median follow-up time of 20 years. A higher adherence to the HNFI was not associated with a lower risk of breast cancer overall, nor of varied hormone receptor status, or when we examining premenopausal and postmenopausal women separately. The multivariable RRs (95 % CI) for breast cancer per 1-point increment in the HNFI were 1.02 (95 % CI 0.98–1.06) for all women, 1.01 (95 % CI 0.95–1.08) for premenopausal women, and 1.02 (95 % CI 0.97–1.07) for postmenopausal women. Conclusion: Adherence to a HNFI was not associated with breast cancer incidence in this cohort of relatively young women, regardless of menopausal status or hormone receptor status.