Lipoprotein(a) levels and risk of cardiovascular disease events in individuals with diabetes mellitus or prediabetes: The Atherosclerosis Risk in Communities study

Background and aims: Diabetes increases risk for atherosclerotic cardiovascular disease (ASCVD). Current guidelines do not recommend measuring lipoprotein(a), another ASCVD risk factor, in these individuals. We examined the association of lipoprotein(a) levels with incident ASCVD events in persons with and without diabetes or prediabetes. Methods: Lipoprotein(a) and other ASCVD risk factors were measured at baseline (1996–1998) in the biracial Atherosclerosis Risk in Communities study; participants without prevalent ASCVD (coronary heart disease or stroke) were monitored ∼15 years for incident ASCVD events. Results: Of 9871 eligible participants (mean age 63 years; 5816 women; 2155 African Americans), 1543 had diabetes and 3615 had prediabetes. Cumulative ASCVD incidence rates (event/1000-person years) were higher in participants with diabetes (26%) or prediabetes (13%) than in nondiabetic individuals (10%, p < 0.001). When comparing highest to lowest lipoprotein(a) categories (≥50 mg/dL vs. ≤10 mg/dL), increasing lipoprotein(a) levels were significantly associated with increasing incident ASCVD events in Caucasian participants with prediabetes (hazard ratio [HR] = 1.35; 95% confidence interval [CI] 1.07–1.69); p = 0.03) and diabetes (HR = 1.42; 95% CI 1.10–1.84; p < 0.01), but not those with normal fasting blood glucose. Adding lipoprotein(a) to Pooled Cohort Equation variables improved risk prediction in persons with diabetes (Δ in area under the receiver operating characteristic curve [AUC] 0.0087, net reclassification index [NRI] 0.1761) and prediabetes (ΔAUC 0.0025, NRI 0.0938). Conclusions: In this biracial cohort, elevated lipoprotein(a) levels in Caucasian individuals with diabetes or prediabetes were associated with further increased ASCVD risk. Adding lipoprotein(a) to traditional risk factors improved ASCVD risk prediction.