Table 1. Baseline characteristics of all the studies included in the meta-analysis.
| Study | Study design | No. of cases | Age (years) | Exposure assessment | Definition of Hypertension | Outcome assessment | Adjustments | NOS |
|---|---|---|---|---|---|---|---|---|
| Harding, 2015, Australia | Cohort | 549 | 11−96 | Measurement | BP ≥ 130/85mmhg | Cancer registry | Sex, age, smoking, education | 7 |
| Wang, 2015, China | Case–control | 43 | 46−61 | Measurement | BP ≥ 140/90mmhg | Medical record | Age, education, breastfeeding, family history of breast cancer, age at menarche, age at menopause, number of full-term pregnancies, and age at first birth | 6 |
| Sun, 2015, China | Cohort | 174 | Median: 56.3 | Physician-diagnosed | NA | Cancer registry | Age, sex, urbanization level, occupation, income, and comorbidity of diabetes, hyperlipidemia, stroke, ischemic heart disease, chronic obstructive pulmonary disease, alcoholism, alcoholic liver damage, and medication of antihypertensive agents | 7 |
| Agnoli, 2015, Italy | Cohort | 593 | 46–61 | Measurement | BP ≥ 130/85mmhg | Cancer registry | Menopausal status, parity, age at menarche, smoking, physical activity, education, alcohol | 7 |
| Chuang, 2015, China | Nested case-control | 1545 | Median: 31–40 | Database | NA | Medical record | Age, occupation, number of screening test before the index date, the average outpatient visit 6 months prior to the index date | 7 |
| Silva, 2015, Brazil | Case-control | 984 | Mean: 55 for case 50.8 for control | Measurement | BP ≥ 140/90mmhg | Histologically confirmed | Age, sex, smoking | 6 |
| Jung, 2013, Korea | Case-control | 287 | Mean: 48 for case 48.3 for control | Questionnaire | NA | Medical record | Age, age of menarche, pregnancy, age of first pregnancy, and family history of breast cancer | 6 |
| Noh, 2013, Korea | Case-control | 270 | 42.2–65.3 | Medical record | BP ≥ 130/85mmhg | Routine health examination. | Age, menopausal status, the time of visit to the Health Promotion Center | 6 |
| Mourouti, 2013, Greece | Case-control | 33 | 44–68 | Questionnaire | BP ≥ 130/85mmhg | Physical biopsy | Work, home places, age | 6 |
| Pereira, 2012, Chilean | Case-control | 340 | Mean: 55.1 | Medical record | BP ≥ 140/90mmhg | Histopathologically confirmed | Age, alcohol use, fruit and vegetable intake, physical activity, type 2 diabetes, use of oral contraceptives, use of hormone replacement therapy, obesity, years of formal education, smoking, number of living births | 6 |
| Ronco, 2012, Uruguay | Case-control | 253 | Mean: 40 | Measurement | NA | Medical record | Age, education, urban/rural status, age at menarche, number of live births, age at first delivery, years between menarche and first delivery, breastfeeding, oral contraception, family history of breast cancer | 7 |
| Bosco, 2012, USA | Cohort | 447 | Median: 50 | Self-reported | BP ≥ 130/85mmhg | Cancer registry | Age, education, BMI at age 18, vigorous activity | 8 |
| Reeves, 2012, USA | Cohort | 551 | ≥65 | Measurement | BP ≥ 130/85mmhg | Pathology report | Age, current hormone use, family history of breast cancer, and other Mets criteria, BMI | 7 |
| Osaki, 2012, Japan | Cohort | 77 | Mean: 58.6 | Medical record | BP ≥ 130/85mmhg | Medical record | Age, smoking status, heavy drinking, presence of metabolic syndrome or pre-metabolic syndrome of each definition | 7 |
| Rosato, 2011, Italy | Case–control | 1063 | 33–86 | Questionnaires | BP ≥ 130/85mmhg | Medical record | Age, study center, study period, education, alcohol consumption, age at menarche, age at first birth, age at menopause, hormone replacement therapy use, and family history of breast cancer | 6 |
| Porto, 2011, Brazil | Case–control | 49 | 40–80 | Questionnaires | BP ≥ 130/85mmhg | Medical record | Age | 6 |
| Largent, 2010, USA | Cohort | 810 | Mean: 52.8 | Questionnaire | NA | Medical record | Race, family history of breast cancer, age at first full-term pregnancy and number of full-term pregnancies combined variable, hormone therapy and menopausal status combined variable, lifetime physical activity, diabetes, BMI, smoking history, alcohol use, hysterectomy, breastfeeding, and quartiles of percent calories from fat | 6 |
| Cook, 2009, USA | Cohort | NA | 30–55 | Questionnaires | NA | Pathology reports | Parity, age at each birth | 6 |
| Inoue, 2009, Japan | Cohort | 59 | 40–69 | Measurements | BP ≥ 130/85mmhg | Cancer registry | Age, study area, smoking status, weekly ethanol intake, total serum cholesterol | 7 |
| Beji, 2007, Turkey | Case–control | 231 | 28–72 | Questionnaire | NA | Histologically confirmed | Age | 6 |
| Largent, 2006, USA | Case–control | 172 | 50–75 | Questionnaire | NA | Medical record | Age, age at first full-term pregnancy, diabetes, family history of breast or ovarian cancer, smoking, alcohol, BMI, menopausal status and education | 7 |
| Lindgren, 2005, Finland | Cohort | 307 | Mean: 51 | Measurements | BP ≥ 160/95mmhg | Cancer registry | Age, year of registration, DBP and SBP as continuous variables, smoking, BMI, use of antihypertensive drugs, functional diagnosis of hypertension and number of children for women | 7 |
| Peeters, 2000, Netherlands | Cohort | 523 | Mean: 57 | Measurements | BP ≥ 160/95mmhg | Cancer registry | Age at baseline, height, BMI, smoking, parity, familial breast cancer, use of oral contraceptives | 8 |
| Weiss, 1999, USA | Case–control | 274 | <45 | Questionnaire | NA | Physician-diagnosed | Age at diagnosis, race. site, menopausal status, age at first birth, number of births, family history, previous breast biopsy, alcohol, BMI, number of mammograms within the 5-year period prior to one year before diagnosis | 6 |
| Soler, 1999, Italy | Case–control | 639 | <75 | Questionnaire | BP ≥ 160/95mmhg | Histologically confirmed | Age, area of residence, education, smoking, alcohol, parity, menopausal status, BMI | 7 |
| Talamini, 1997, Italy | Case–control | 86 | 20–74 | Questionnaire | NA | Histologically confirmed | Study area, age, education, parity, BMI, menopausal status | 6 |
| Moseson, 1993, USA | Case–control | 148 | 22–84 | Physician-diagnosed | NA | Biopsy | Age, family history of breast cancer, age at first full-term birth, height, screening variables, null parity, Jewish religion, Latin American birthplace | 7 |
| Franceschi, 1990, Italy | Case–control | 501 | Mean: 45–54 | Physician-diagnosed | NA | Histologically confirmed | Terms for medical condition or procedure, age, area of residence, education, age at first birth, menopausal status and, except for severe overweight, BMI | 6 |
| Thompson, 1989, USA | Case–control | 635 | <55 | Physician-diagnosed | NA | Histologically confirmed | Age and geographic region. | 5 |
NA, not available; NOS, Newcastle–Ottawa Quality Assessment Scale; BP, blood pressure; DBP, diastolic blood pressure; SBP, systolic blood pressure; BMI, body mass index; USA, united states of America; Mets, metabolic syndrome.