Hypertension and the Risk of Breast Cancer in Chilean Women: a Case-control Study

Background: Breast cancer is the most common cancer in women worldwide. Although different metabolicfactors have been implicated in breast cancer development, the relationship between hypertension and breastcancer has not been elucidated. Aim: To evaluate hypertension as a risk factor for breast cancer in Chilean womenof low and middle socio-economic status.
Methods: We conducted an age-matched (1:1) case-control study in 3hospitals in Santiago, Chile. Breast cancer cases (n=170) were histopathologically confirmed. Controls had beenclassified as Breast Imaging Reporting and Data System I (negative) or II (benign findings) within 6 months ofrecruitment. Blood pressure was measured using a mercury sphygmomanometer and standardized procedures.We used 2 hypertension cut-off points: blood pressures of ≥140/90 mmHg and ≥130/85 mmHg. Fasting insulin andglucose levels were assessed, and anthropometric, sociodemographic, and behavioral information were collected.Odds ratios and 95% confidence intervals were estimated for the entire sample and restricted to postmenopausalwomen using multivariable conditional logistic regression models.
Results: Hypertension (≥140/90 mmHg) wassignificantly higher in cases (37.1%) than controls (17.1%) for the entire sample and in postmenopausal pairs(44.0% compared to 23.8%). In crude and adjusted models, hypertensive women had a 4-fold increased risk ofbreast cancer (adjusted odds ratio: 4.2; 95% confidence interval: 1.8; 9.6) compared to non-hypertensive womenin the entire sample. We found a similar association in the postmenopausal group (adjusted odds ratio: 2.8; 95%confidence interval: 1.1; 7.4). A significant effect was also observed when hypertension was defined as bloodpressure of ≥130/85 mmHg.
Conclusion: A significant association was found between hypertension and breastcancer over the entire sample and when restricted to postmenopausal women. Hypertension is highly prevalentin Latin America and may be a modifiable risk factor for breast cancer; therefore, a small association betweenhypertension and breast cancer may have broad implications.