Interaction Of Lipoprotein(a) With Low-density Lipoprotein Cholesterol On First Incident Acute Myocardial Infarction

Object:To evaluate the interaction effects between lipoprotein(a)(Lp(a))and low-density lipoprotein cholesterol(LDL-C)on first incident MI among Chinese Han population.Method:1522 cases with initial MI and 1691 controls without coronary heart disease(CHD)confirmed with coronary angiography were retrospectively analyzed using logistic regression model.All the subjects were grouped(Q1-Q5)according to the quintile partitioning of the Lp(a)level.Higher LDL-C levels were defined as>2.6mmol/L.Together considering the Lp(a)quintiles and the LDL-C levels,we made up 4 groups:1)Reference group:patients with Lp(a)levels in Q1 and with LDL-C<2.6mmol/L;2)Group for higher Lp(a)levels alone:patients with higher Lp(a)levels in Q2-Q5,but with LDL-C levels<2.6mmol/L;3)Group for higher LDL-C levels alone:patients with higher LDL-C levels≥2.6mmol/L,but with Lp(a)levels in Q1;and 4)Group for both higher LDL-C levels≥2.6mmol/L and higher Lp(a)levels in Q2-Q5.We evaluated the interactions with the measures of effect modification on both additive(Relative excess risk due to interaction,RERI)and multiplicative scales.The crude or multivariable-adjusted ORs were reported.Results:Compared with the reference group,the multivariable-adjusted ORs(95%CI)of initial AMI for higher LDL-C levels alone is 2.66(1.78-3.98);for higher Lp(a)levels alone in Q2-Q5 are 1.51(1.07-2.15),1.84(1.28-2.64),1.86(1.30-2.67)and 2.66(1.88-3.76),respectively;and for both higher LDL-C levels and higher Lp(a)levels are 3.95(2.64-5.92),3.20(2.21-4.64),5.64(3.80-8.36)and 7.48(4.90-11.44),respectively.The multivariable-adjusted ORs start to accelerate from Q3 of Lp(a).RERI(95%CI)are 1.78(0.12-3.44),3.01(0.58-5.44),at Q4 and Q5 of Lp(a),respectively,indicating the presence of additive interactions.But there is no interactions between LDL-C and Lp(a)on multiplicative scale.Conclusion:Lp(a)interacts with LDL-C in initial AMI on an additive scale in Chinese Han population.The risk of AMI from exposure of both elevated Lp(a)and elevated LDL-C is much greater than the sum of the risks from that of both alone.For those with combined elevation of LDL-C and Lp(a),we recommend that LDL-C lowering therapy,considering Lp(a)lowering therapy,be a cornerstone.The Lp(a)level<90mg/L(rounded median of Q3 of Lp(a))may be an optimal option for those with stubborn elevated LDL-C levels,which will help in primary prevention of AMI.