Evidence From Humans
 
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Obesity, body size, and risk of postmenopausal breast cancer: the Women's Health Initiative (United States)
Morimoto, L. M., White, E., Chen, Z., Chlebowski, R. T., Hays, J., Kuller, L., Lopez, A. M., Manson, J., Margolis, K. L., Muti, P. C., Stefanick, M. L., McTiernan, A. Cancer Causes & Control. 2002. 13:8, 741-51.
Topic area
Body size
Study design
Prospective Cohort
Funding agency
Other: NIH
Study Participants
Number of Cases
1030 (invasive only)
Menopausal Status
The menopausal status of women included in this study is listed here.
Post menopausal
Number in Cohort
Cohort: 85,917
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: postmenopausal women; age 50-79 at enrollment; enrolled in the Women's Health Initiative Observational Study between 10/1/93 and 12/31/98; diagnosed with invasive breast cancer by April 2000 Ex: In situ cases, women with a history of breast cancer at enrollment; women whose age at menopause was undeterminable; women younger than 55 at baseline; women who had a bilateral mastectomy; women without a follow-up period
Comment about participation selection
Strengths: Large cohort; baseline anthropometric measurements were performed by trained and certified staff; assessed many exposures; stratified analysis by HRT use which gives more accurate results when analyzing BMI and breast cancer risk; analyzed BMI at 50 years of age which consistently predicted breast cancer among all age groups (BMI amongst older post women is not as predictive since these women lose height with age and have a lower lean muscle to fat ratio than younger women); results on adult weight gain and post weight gain among non-HRT users were significant and consistent with findings from several previous cohorts; adjusted for physical activity and dietary energy intake Limitations: possible selection bias due to the large number of exclusion factors; only 30% of study population had never used HRT; height and weight measures at earlier ages were taken from questionnaire data which may not be as accurate as baseline measurements; mean follow-up time was only 2.9 years;
Exposures investigated
Height; BMI at 18 years; weight; BMI at baseline; BMI at age 50; maximum BMI; BMI changes (baseline-age 18); BMI changes (baseline-age 50); waist circumference; hip circumference; waist to hip ratio
How exposure was measured
Questionnaire, self-administered Anthropometric measurement, researcher-administered
Statistical Analysis
Ethnic groups with separate analysis
If this study provided a separate analysis by ethnic or racial group, the groups are listed here.
No
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: age, education, age at menopause, parity, age at first birth, first degree family history of breast cancer, smoking status, age at menarche, race, alcohol consumption, exercise, and dietary energy intake
Genetic characterization included
If the study analyzed relationships between environmental factors and inherited genetic variations, this field will be marked “Yes.” “No”, if not.
No
Description of major analysis
Effect modifiers: HRT use and age Interaction: HRT use Follow-up: mean 2.0 years
Strength of associations reported
Association between postmenopausal breast cancer risk and height, >167.0 cm vs. <156.4 cm, RR=1.27(1.00-1.62) trend p=0.09
Association between postmenopausal breast cancer risk and weight among women who had never used HRT, >82.2 kg vs. <58.7 kg, RR=2.85(1.81-4.49) trend p<0.001
Association between postmenopausal breast cancer risk and weight amongst current and former users of HRT, >82.2 kg vs. <58.7 kg, RR=0.91(0.68-1.21) trend p=0.73
Association between postmenopausal breast cancer risk and BMI among women who had never used HRT, >31.1 vs. <22.6, RR=2.52(1.62-3.93) trend p<0.001
Association between postmenopausal breast cancer risk and BMI amongst current and former users of HRT, >31.1 vs. <22.6, RR=0.96(0.73-1.27) trend p=0.75
Association between postmenopausal breast cancer risk and maximum BMI among women who had never used HRT, >31.1 vs. <22.6, RR=2.24(1.31-3.84) trend p<0.001
Association between postmenopausal breast cancer risk and BMI among women age 50-59 years old, >31.1 vs. <22.6, RR=4.46(1.60-12.44) trend p=0.01
Association between postmenopausal breast cancer risk and BMI among women age 60-69 years old, >31.1 vs. <22.6, RR=4.91(2.15-11.18) trend p<0.001
Results Comments
No significant association between breast cancer and WHR among both HRT users and non-users.
Author address
Fred Hutchinson Cancer Research Center, Seattle, WA, USA.
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