Environment and Breast Cancer: Science Review

Evidence From Humans
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Obesity and hormone-dependent tumors: cohort and co-twin control studies based on the Swedish Twin Registry
Jonsson, F., Wolk, A., Pedersen, N. L., Lichtenstein, P., Terry, P., Ahlbom, A., Feychting, M. International Journal of Cancer. 2003. 106:4, 594-9.
Topic area
Body size
Study design
Prospective cohort of same sex twin pairs
Funding agency
Other: Swedish Cancer Society
Study Participants
Number of Cases
607 (421 in analysis)
Menopausal Status
The menopausal status of women included in this study is listed here.
Pre menopausal
Post menopausal
Number in Cohort
Cohort: 11,598 females (21,884 total)
Cohort participation rate
Retention/participation exceeded 70% for exposed a
Participant selection: Inclusion and exclusion criteria
Criteria used to select participants in the study.
In: Swedish Twin Registry: same sexed twin pairs, born between 1886-1925 and both twins living in Sweden in 1961 Ex: Women deceased before 1969 and prevalent cancers at baseline (1961)
Comment about participation selection
Strengths: Large cohort, Swedish Cancer Registry is 98-99% complete for cancers of the breast and co-twin control analysis allowed for the unaffected twin to be treated as a matched control to the twin with the disease Limitations: Height and weights were collected once at the beginning of the 29 year study period, anthropometric measurements were self reported and due to a median baseline age of 56 years there were few premenopausal cases (38)
Exposure Investigated
Exposures investigated
BMI, weight change and height
How exposure was measured
Questionnaire, self-administered
Exposure assessment comment
Anthropometric measurements were self reported
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.
Adequately controlled, Confounders:education, smoking habits, alcohol consumption, physical activity, parity, menopausal status, (all results were adjusted for age)
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
Effect modifiers: age at diagnosis Follow up: maximum follow up 29 yrs (median for women 26 yrs)
Strength of associations reported
Association between breast cancer risk and BMI among women >70 yrs at diagnosis, > 30 vs. 18.5-24.99, OR = 1.6 (1.1-2.4)
Association between breast cancer risk and women with a high BMI at age 25, > 25 vs 18.50-24.99, OR = 0.5 (0.3-0.8)
Association between breast cancer risk and weight gain between age 25 yrs and baseline, > 21 kg vs 0-5 kg, OR= 2.1 (1.3-3.3)
Association between breast cancer risk and height, > 168.5 cm vs 159-163cm, OR= 1.5 (1.1-2.0)
Author address
Institute of Environmental Medicine, Karolinska Institute, Stockholm, Sweden.