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Table 1 Basic characteristics of 10 studies

From: Reproductive factors and breast cancer risk according to joint estrogen and progesterone receptor status: a meta-analysis of epidemiological studies

Study Source of study subjects Age (years) Source of receptor information (percentage of subjects with the information) Number of subjects Adjustment for potential confounders in data analyses
  Cases Controls    ER+PR+/ER-PR- cases Controls  
Cohort studies
[9] Iowa Women's Health Study, USA (7 years' follow-up, 1986–1992, 241,627 person-years)   55–69 at baseline Medical record (65%) 414/80 - BMI, BMI at age 18 years, WHR, age at menarche, type of MP, age at MP, oophorectomy history, FHBC, parity, age at first live birth, contraceptive, non-contraceptive estrogen use, ALC
[10] Nurses' Health Study Cohort, USA (20 years' follow-up, 1980–2000, 1,029,414 person-years)   30–55 at baseline in 1976 Medical record (74%) 1,281/417 - Age, age at menarche, time since menopause, parity at age, age at birth, FHBC, HBBD, years on ET, years on EPT, BMI, height, ALC
Population-based case-control studies
[11] North Carolina, USA DMV/HCFA 20–74 Majority from medical record (91%) 381/262 790 Age at menarche, nulliparity/age at first full-term pregnancy, breastfeeding, abortion or miscarriage, BMI, WHR, OC, HT, FHBC, medical radiation to the chest, SMK, ALC, education, age, race
[12] Georgia, Washington, and New Jersey, USA RDD 20–44 Medical record (78%) 616/360 1,397 Age, race, education, BMI, WHR, parity, age at first birth, breastfeeding, OC, SMK, ALC, recreational exercise at age 12–13 and 1 year prior to interview, age at menarche, FHBC, MP, geographic site
[13] Ontario, Canada Assessment roll of the Ministry of Finance 25–74 Hospital laboratories and medical record (87%) 1,901/737 3,691 Age, age at menarche, parity, age at first live birth, OC, BMI, ALC, SMK, breastfeeding, HBBD, FHBC, current strenuous activity for pre-MP women; age at MP, HT, and oophorectomy history for post-MP women
[14] Victoria and New South Wales, Australia Electoral roll <40 Medical record (81%) 323/181 564 Age, study center, study period, education, country of birth, marital status, FHBC, BMI, age at menarche, number of live births, OC
[7] Georgia, Washington, Michigan, Pennsylvania, and California, USA RDD 35–64 Medical record (82%) 2,130/1081 4,668 Age, race, education, FHBC, age at menarche, study site, number of full-term pregnancies and age at first full-term pregnancy only for models of parous women
[8] California, USA Neighbours 20–49 Medical record (84%) 854/385 440 Age, race, education, FHBC, age at menarche, gravidity, number of full-term pregnancies, OC, BMI, ALC, MP and HT, age at first full-term pregnancy and breastfeeding only for parous women
Hospital-based case-control studies
[15] Aichi Cancer Hospital, Nagoya, Japan Hospital ≥25 Not specified (40%) 176/141 21,714 Age, occupation, FHBC, age at menarche, menstrual regularity as a teenager, age at MP, age at first full-term pregnancy, number of full-term pregnancies, breastfeeding, ALC, SMK
[16] Yale, New Haven Hospital, USA Hospital 40–80 Single laboratory (76%) 104/107 401 Age, race, FHBC, age at menarche, nulliparity/age at first full-term pregnancy, breastfeeding, MP, BMI, ever estrogen use, ALC, SMK
  1. ALC, alcohol drinking; BMI, body mass index; DMV/HCFA, Division of Motor Vehicles for women under 65 years/Health Care Financing Administration for women aged 65 years or older; EPT, estrogen and progestin therapy; ER+, estrogen receptor-positive; ER-, estrogen receptor-negative; ET, estrogen therapy; FHBC, family history of breast cancer; HBBD, history of breast benign diseases; HT, hormone therapy; MP, menopausal or menopause; OC, oral contraceptive use; PR+, progesterone receptor-positive; PR-, progesterone receptor-negative; RDD, random digit dialing; SMK, cigarette smoking; WHR, waist-hip ratio.