Abstract 3982: Lipoprotein(a), Hormone Replacement Therapy and the Risk of Future Cardiovascular Disease in Women
BACKGROUND: While multiple studies indicate that hormone replacement therapy (HRT) decreases plasma levels of lipoprotein (a) (Lp(a)), whether this effect alters the relationship of Lp(a) with cardiovascular risk is unknown.
METHODS: Lp(a) was measured at baseline among 27,791 initially healthy women of whom 12,075 were on HRT and 15,661 were not. The risk of first-ever major cardiovascular event over a ten-year period (nonfatal myocardial infarction, nonfatal cerebrovascular event, coronary revascularization or cardiovascular deaths) was assessed in Cox-proportional hazard models according to baseline Lp(a) levels and HRT status, and adjusted for confounding variables.
RESULTS: As anticipated, Lp(a) values were lower among women taking HRT (median 9.4 vs. 11. 6 mg/dL, P<0.0001). Furthermore, in women not taking HRT, the hazard ratio of future cardiovascular disease for the highest Lp(a) quintile compared to the lowest was 1.7 (P-trend among quintiles <0.0001). In contrast, among women taking HRT, there was no elevation of cardiovascular risk seen [hazard ratio 1.1, P-trend =0.20]. Interaction between HRT and Lp(a) quintiles on CVD was significant (P-interaction = 0.005).
CONCLUSIONS: The relationship of high Lp(a) levels and incident cardiovascular events is modified by hormone replacement therapy in women.