The combined effect of cardiovascular risk factors on breast cancer in women is unknown. The relationship between genetic risk combined with cardiovascular health (CVH) levels and breast cancer has not been confirmed. This study aims to explore the relationship between CVH level based on life's essential 8 (LE8) score and breast cancer risk in women with different menopausal statuses and to estimate further the effect of CVH level combined with genetic susceptibility on breast cancer risk. A total of 118,911 women from UK Biobank were included in the study, including 22,676 premenopausal women and 96,235 postmenopausal women. The association between the CVH level and the risk of breast cancer in women with different menopausal statuses was assessed using the Cox proportional hazards regression models, with the healthiest CVH group as the reference. In addition, risk ratios (HRs) and 95% confidence intervals (95% CIs) for the joint effect of the CVH level and polygenic risk score (PRS) were calculated using the PRS from the UK Biobank. During a mean follow-up period of 13.8 years, we observed 733 cases and 3,645 cases of breast cancer in premenopausal and postmenopausal women, respectively. In premenopausal women, the risk of breast cancer was significantly increased in the intermediate CVH group (HR, 1.28; 95%CI 1.08-1.52) and the low CVH group (HR, 1.44; 95%CI 1.13-1.85). In postmenopausal women, the risk of incidence was also significantly increased in the intermediate CVH group (HR, 1.20; 95%CI 1.07-1.32) and the low CVH group (HR, 1.34; 95%CI 1.17-1.54). In the joint effect analysis, the risk of breast cancer for women in the low CVH group and the high genetic risk group was highest in both premenopausal (HR, 8.26; 95%CI 4.44-15.35) and postmenopausal (HR, 8.10; 95%CI 5.50-11.93) women. Women with lower LE8 scores and higher genetic susceptibility have the higher risk of breast cancer. This suggests that women with lower levels of CVH and higher genetic susceptibility have an increased risk of breast cancer under different menopausal statuses.
