6th International Workshop on Breast Densitometry and Breast ...

6 th <strong>International</strong> <strong>Workshop</strong> on Breast Densitometry
and Breast Cancer Risk Assessment
P14 THE ASSOCIATION BETWEEN VITAMIN D INTAKE, SEASON AND
MAMMOGRAPHIC DENSITY IN NORWEGIAN POSTMENOPAUSAL WOMEN
Merete Ellingjord-Dale¹, Isabel dos Santos Silva ² , Tom Grotmol³, Solveig Hofvind³, Lene Frost
Andersen¹, Samera Azeem Qureshi¹, Marianne Skov Markussen¹, Elisabeth Couto⁵, Giske Ursin 1,3,4
1 University of Oslo, Norway, 2 London School of Hygiene and Tropical Medicine, UK , 3 Cancer Registry of
Norway, Norway, 4 University of Southern California, USA, ⁵Norwegian Knowledge Centre for the Health
Services, Norway
ABSTRACTS
Background: It is unclear whether vitamin D intake is associated with breast cancer risk. There is some,
albeit inconsistent, evidence that mammographic density (MD) varies by season of the year or by vitamin
D intake. We evaluated the association of MD with seasonality and vitamin D intake among a subset of
women who participated in the Norwegian Breast Cancer Screening Program (NBCSP) in 2004 or in
2008.
Methods: We conducted a cross-sectional study to examine the association of MD with vitamin D intake
and seasonality among 2662 postmenopausal women aged 50-69 years. Vitamin D intake (estimated with
and without taking into account supplement use) was ascertained through a self-administered
questionnaire. Density on digitized analogue films was measured using a computer assisted method
(Madena, University of Southern California). Linear regression methods were used to determine the
association of MD with vitamin D intake and the season in which the mammogram was obtained.
Specifically we estimated least square means of MD across categories of the exposure variables, while
adjusting for potential confounders.
Results: There was no association between intake of vitamin D and MD, across quartiles of vitamin D
intake (0-5, 6-8, 9-12 and 13-49 mcg per day, estimated with supplements). Mean MD was 18.5%
(SD=15.3%) in women with the lowest, and 18.9% (SD=15.6%) in women with the highest intake of
vitamin D (p for trend=0.73). There was no association between vitamin D intake and MD in women who
had their mammogram during January-May, i.e. at the time when vitamin D levels are presumed to be at
the lowest (p for trend= 0.10).
Similarly, there was no statistical significant association between month of mammography and MD in
either the 2004 or the 2008 data.
Conclusion: Our cross-sectional study found no evidence of an association of MD with vitamin D intake
or month/season of mammography.
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