Abstract 1277: The association between seasonality, vitamin D and calcium intake and mammographic density in Norwegian postmenopausal women

Abstract

Abstract Background: Mammographic density (MD) is one of the strongest known breast cancer risk factors. The role of vitamin D in breast cancer etiology is unclear. The evidence of an association between Vitamin D and MD is limited and inconsistent, as is the seasonal variation of MD. We evaluated the association between MD and season/month the mammogram was obtained, as well as vitamin D intake, energy and calcium intake in a population of women from Norway, a country with limited sunlight exposure for a large part of the year. Methods: We studied 2662 postmenopausal women aged 50-69 who participated in the Norwegian Breast Cancer Screening Program (NBCSP) in 2004 or 2006/07. Women completed risk factor and food frequency questionnaires (FFQ). Vitamin D and calcium intake was assessed with and without taking supplements into consideration. Month of mammogram was recorded from the mammogram. MD was assessed using a computer assisted method (Madena, University of Southern California). We used linear regression to determine the association between month of mammogram and MD, as well as vitamin D and calcium intake (assessed from the FFQ) and MD, adjusting for age, education, body mass index (BMI), parity and postmenopausal estrogen and progestin therapy. We also examined the association between vitamin D, calcium and MD by season (month) the mammogram was obtained. Results: Age, BMI and parity were inversely associated with MD, while education and postmenopausal estrogen and progestin therapy were positively associated\ with MD. There was no association between quartiles of vitamin D or calcium intake and MD, regardless of whether the nutrients were estimated with our without supplements. We found no association between season (month) and MD. There was no evidence for an inverse association between vitamin D intake and MD when women were stratified by the month the mammogram was obtained. Conclusion: Our results provide no support for a protective effect of dietary vitamin D intake against increased MD. We found no evidence that season or month the mammogram was obtained, was associated with MD. Citation Format: Merete Ellingjord-Dale, Isabel dos Santos Silva, Tom Grotmol, Amrit Kaur Sakhi, Samera Qureshi, Solveig Hofvind, Marianne Skov Markussen, Elisabeth Couto, Lene Frost Andersen, Giske Ursin, Giske Ursin. The association between seasonality, vitamin D and calcium intake and mammographic density in Norwegian postmenopausal women. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 1277. doi:10.1158/1538-7445.AM2014-1277