Abstract
Background: Dietary vitamin D has been associated with lower mammographic breast density, a strong biomarker for breast cancer risk. Blood 25-hydroxyvitamin D [25(OH)D] is an integrated measure of vitamin D status (from food, supplements, and sun exposure) and varies with season. Our objective was to assess seasonal variations of breast density and compare such variations, if any, with that of 25(OH)D.
Methods: This cross-sectional study includes 741 premenopausal women recruited at screening mammography. Plasma 25(OH)D at recruitment was measured by RIA. Breast density was evaluated using a computer-assisted method. Seasonal variations were modeled using multivariate linear regression and semi-parametric cubic smoothing splines.
Results: Season was strongly associated with 25(OH)D (P < 0.0001). The highest smoothed mean 25(OH)D levels were seen at the end of July (81.5 nmol/L) and the lowest in mid-April (52.4 nmol/L). Breast density showed modest seasonal variations (P = 0.028). The lowest smoothed mean breast density was observed in early December (38.5%) and the highest at the beginning of April (44.3%). When a 4-month lag time was presumed, seasonal variations of breast density appeared to be a mirror image of those of 25(OH)D, and the correlation of daily smoothed estimates of mean breast density and 25(OH)D was negative and strong (r = −0.90).
Conclusion: In premenopausal women, changes in blood vitamin D seem to be inversely related to changes in breast density with a lag time of about 4 months. This finding encourages further investigation of the possibility that vitamin D could reduce breast density and breast cancer risk. (Cancer Epidemiol Biomarkers Prev 2007;16(5):929–33)
- breast density
- breast cancer
- 25-hydroxyvitamin D
- vitamin D
- seasonal variations
- prevention
- lag time
Footnotes
-
Grant support: Translation Acceleration Grants Program for Breast Cancer Control of the Canadian Breast Cancer Research Alliance and Canadian Institutes of Health Research and the Canadian Cancer Etiology Research Network of the National Cancer Institute of Canada; The Cancer Research Society, Inc. and Canadian Institutes of Health Research fellowships (C. Diorio); and Canadian Institutes of Health Research and National Cancer Institute of Canada studentships (M. Sinotte).
-
The costs of publication of this article were defrayed in part by the payment of page charges. This article must therefore be hereby marked advertisement in accordance with 18 U.S.C. Section 1734 solely to indicate this fact.
- Accepted February 19, 2007.
- Received September 1, 2006.
- Revision received February 7, 2007.
Volume 16, Issue 5
