Mildly elevated diastolic blood pressure increases subsequent risk of breast cancer in postmenopausal women in the Health Examinees-Gem study.

Epidemiological evidence suggests that hypertension is associated with breast cancer risk. However, previous studies disregard blood pressure components in the healthy population. We aimed to examine the relationship between systolic and diastolic blood pressure and breast cancer risk in a Korean population-based prospective cohort. A total of 73,031 women from the Health Examinees Gem Study were followed from baseline (2004 to 2013) through 2018. Systolic and diastolic blood pressure were measured by trainee physicians at baseline recruitment and then categorized based on the international guidelines for clinical hypertension. Associations between systolic and diastolic blood pressure with overall breast cancer and stratified by premenopausal and postmenopausal status were evaluated using adjusted multivariable Cox proportional hazard regression. A total of 858 breast cancer cases were recorded for a median follow-up period of 9 years. Compared with the normal DBP category (< 85 mmHg), the normal-high category was positively associated with breast cancer risk in postmenopausal women (85-89 mmHg, HR 1.73 95% CI 1.28-2.33), but not in premenopausal women (85-89 mmHg, HR 0.87 95% CI 0.56-1.35). Similar results were found when all cases of self-reported hypertension were excluded. Results for SBP did not show a significant association with breast cancer risk. The association between DBP and breast cancer suggests DBP could be an important factor in cancer prevention, especially for women after menopause. Our study provides a first detailed approach to understanding the importance of diastolic blood pressure for breast cancer prevention and warrants further investigation.