Serum total cholesterol and the risk of breast cancer in postmenopausal Korean women

Objective: To evaluate an association between serum total cholesterol level and breast cancer risk, for which inconsistent findings have been reported in spite of the role of serum cholesterol as a precursor to a breast cancer-related sex steroid hormone. Methods: Postmenopausal Korean women (n = 170,374), categorized into four groups by quartiles of cholesterol level, were followed up for occurrence of breast cancer from 1993 to 2003. Relative risks were assessed by Cox proportional hazard analysis. Results: A positive association between cholesterol level and breast cancer risk was found with 31% greater age-adjusted risk of breast cancer in the highest cholesterol group (≥5.95 mmol/l) than that in the lowest cholesterol group (<4.63 mmol/l). The strength of association was reduced slightly but persisted after the adjustment for reproductive and behavioral covariates. However, the association further attenuated and the positive trend was no longer significant when BMI was additionally adjusted (p-trend, 0.0684). Stratified analysis by BMI showed that the risk of breast cancer increased with increasing cholesterol level only in normal BMI (<25 kg/m²) group, but the interaction term was not significant. Conclusion: Serum total cholesterol level is not associated with the risk of breast cancer in postmenopausal Korean women.