Environment and Breast Cancer: Science Review

Evidence From Humans
Print this page
Risk of breast cancer in prematurely born women
Ekbom, A., Erlandsson, G., Hsieh, C., Trichopoulos, D., Adami, H. O., Cnattingius, S. J Natl Cancer Inst. 2000. 92:10, 840-1.
Topic area
Early life exposures
Study design
Cohort study
Funding agency
Not reported
Study Participants
Menopausal Status
The menopausal status of women included in this study is listed here.
Number in Cohort
Cohort: 273
Participant selection: Inclusion and exclusion criteria
Criteria used to select participants in the study.
In: Girls born before the 35th gestational week and those with a birth weight under 2000g regardless of gestational age, in Stockholm, Sweden from 1925 through 1934 and were still alive on January 1, 1958
Exposure Investigated
Exposures investigated
Premature gestational age at birth
How exposure was measured
Other: Birth records
Exposure assessment comment
Accuracy of week of gestation at birth in 1925 through 1934, few cases in all strata of gestational age
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.
Race, BMI, parity, menopausal status, 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
SIR (rates of observed-to-expected numbers of cancers) with 95% CI, stratified analysis in four groups of gestational age (GA) in weeks: GA 29-30 weeks, GA 31-32, GA 33-34, GA>=35; follow-up: 1958-1992
Strength of associations reported
GA <31 weeks: 6.7 (1.4 -19.5), GA >= 35 weeks: 0.2 (0.01 -1.3)
Results Comments
Women born before the 33th gestational week had a substantially increased risk of breast cancer.
Author address
Department of Medical Epidemiology, Karolinska Institutet, Stockholm, Sweden. Anders.Ekbom@mep.ki.se
Reviewers Comments
Results based on 1 to 5 cases per strata without analysis of confounders