Abstract
The possible association between breast cancer and oral contraceptive use before the age of 20 was investigated using Icelandic population-based information from women born after 1944. The design was a nested case-control study within a cohort, using data on duration of oral contraceptive use at young ages. The availability of oral contraceptives before the age of 20 has changed dramatically and is highly dependent on birth years, with 20% and 82% starting before the age of 20 among Icelandic users born in 1945-47 and 1963-67 respectively. The association between total duration of oral contraceptive use and breast cancer was significantly dependent on year of birth. In women born in 1951-67 (based on 81 cases), the relative risk (RR) associated with use for more than 4 years was 2.0 (95% CI 1.1-3.7). The association disappeared when women born in 1945-50 were included (RR 1.1,95% CI 0.8-1.6), adding 123 cases. A significant trend of increased risk with longer duration was present only in the group born after 1950, with RR 0.9, 1.7 and 3.0 for < or = 4 years, >4-8 years and > 8 years of use respectively. The results of this study indicate an association between breast cancer and oral contraceptive use at a young age. They also stress the importance of distinguishing between groups with different opportunities for exposure at young age.
This is a preview of subscription content, access via your institution
Access options
Subscribe to this journal
Receive 24 print issues and online access
$259.00 per year
only $10.79 per issue
Buy this article
- Purchase on Springer Link
- Instant access to full article PDF
Prices may be subject to local taxes which are calculated during checkout
Similar content being viewed by others
Author information
Authors and Affiliations
Rights and permissions
About this article
Cite this article
Tryggvadóttir, L., Tulinius, H. & Gudmundsdóttir, G. Oral contraceptive use at a young age and the risk of breast cancer: an Icelandic, population-based cohort study of the effect of birth year. Br J Cancer 75, 139–143 (1997). https://doi.org/10.1038/bjc.1997.23
Issue Date:
DOI: https://doi.org/10.1038/bjc.1997.23
This article is cited by
-
Oral contraceptive use before first birth and risk of breast cancer: a case control study
BMC Women's Health (2002)