Lipoprotein(a) and Risk of Incident Atherosclerotic Cardiovascular Disease: Impact of High-Sensitivity C-Reactive Protein and Risk Variability Among Human Clinical Subgroups

<b>Background/Objectives:</b> Elevated lipoprotein(a) [Lp(a)] is associated with increased incidence of atherosclerotic cardiovascular disease (ASCVD). We aimed to assess the utility of Lp(a) as an ASCVD risk-enhancing factor, as recommended by the 2019 ACC/AHA guidelines on ASCVD primary prevention, and to determine whether C-reactive protein (CRP) modifies the association of elevated Lp(a) with ASCVD risk. <b>Methods:</b> Lp(a), high sensitivity CRP (hs-CRP), and other ASCVD risk factors, including blood lipids, blood pressure, diabetes status, body weight and height, and smoking, were measured in 15,933 participants (median age 61.7 years with 25th-75th percentiles 57-68 years, 56.7% female, 19.7% Black, free of ASCVD at baseline) in the Atherosclerosis Risk in Communities Study, Framingham Offspring Study, and Multi-Ethnic Study of Atherosclerosis. Participants were followed for 10 years for incident ASCVD (coronary heart disease (CHD) or stroke) and CHD (including angioplasty and/or coronary artery bypass but minus stroke). These endpoints occurred in 9.7% and 7.4% of subjects, respectively. <b>Results:</b> Compared with the lowest Lp(a) category (<10 mg/dL), the highest Lp(a) category (≥50 mg/dL) carried a significantly increased incidence of ASCVD (hazard ratio [HR] = 1.31; 95% confidence interval [CI] 1.15-1.50; <i>p</i> < 0.001) and CHD (HR = 1.49; 95%CI 1.27-1.75; <i>p</i> < 0.001). The association of elevated Lp(a) with incident ASCVD was stronger in males and non-Black individuals and was independent of diabetes status. Lp(a) levels ≥ 50 mg/dL predicted the 10-year ASCVD risk for those at intermediate risk (≥7.5%, HR = 1.32; 95%CI 1.15-1.52; <i>p</i> < 0.001). There was a significant interaction between Lp(a) and hs-CRP; individuals with concomitant elevated levels of Lp(a) and hs-CRP had the highest ASCVD risk. <b>Conclusions:</b> Elevated Lp(a) levels were associated with increased ASCVD risk, particularly in individuals with concomitantly elevated hs-CRP levels and those at intermediate 10-year ASCVD risk.