Environment and Breast Cancer: Science Review

Evidence From Humans
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Birth weight and risk of early-onset breast cancer (Denmark)
Mellemkjaer, L., Olsen, M. L., Sorensen, H. T., Thulstrup, A. M., Olsen, J., Olsen, J. H. Cancer Causes Control. 2003. 14:1, 61-4.
Topic area
Early life exposures
Study design
Population based case-control
Funding agency
Other: Oncologic Research Unit, Danish Cancer Soci
Study Participants
Menopausal Status
The menopausal status of women included in this study is listed here.
Number of Controls
Controls: 3423
Participant selection: Inclusion and exclusion criteria
Criteria used to select participants in the study.
In: cases women identified by the Danish Cancer Registry as having had a breast cancer below the age of 40 years during the period 1943-1990 and born after 1935 in the Northern and central part of Jutland in Denmark Controls: were women registered in the midwives' report immediately before or after the case, matched on midwifes and time of birth. Ex: women who had no available midwives's report (twins or adopted), had the values for birth related variables out of range or missing, controls were excluded if they had died or emigrated before the age at which the case was diagnosed with cancer.
Exposures investigated
Birthweight, maternal age
How exposure was measured
Other: Midwives records
Statistical Analysis
Breast cancer outcome investigated
Primary incident breast cancer
Ethnic groups with separate analysis
If this study provided a separate analysis by ethnic or racial group, the groups are listed here.
Confounders considered
Other breast cancer risk factors, such as family history, age at first birth, and hormone replacement therapy use, that were taken into account in the study.
BMI, race, parity, alcohol consumption, family history of breast cancer
Genetic characterization included
If the study analyzed relationships between environmental factors and inherited genetic variations, this field will be marked “Yes.” “No”, if not.
Description of major analysis
Conditional logistic regression model conditioned on midwife, age at time of birth, and additionally adjusted for marital status of the mother, and other early life exposures. Adjusted OR with 95% CI, analysis as categorical data: Birthweight>=4000g versu
Strength of associations reported
Birthweight: 1.25 (1.00-1.55); mother's age: 1.11 (0.90-1.36)
Results Comments
A high birthweight of more than 4000g is positively associated with early onset breast cancer, increasing maternal age slightly increase risk of early onset breast cancer.
Author address
Institute of Cancer Epidemiology, Danish Cancer Society, Copenhagen, Denmark. lene@cancer.dk