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Associations Between Lipoprotein(a) Levels and Cardiovascular Outcomes in African Americans and Caucasians: The Atherosclerosis Risk in Communities (ARIC) Study
Study Questions:
What is the association between lipoprotein(a) [Lp(a)] and incident cardiovascular disease (CVD) events in African Americans and Caucasians in the Atherosclerosis Risk in Communities (ARIC) study?
Methods:
Plasma Lp(a) was measured in African Americans (n = 3,467) and Caucasians (n = 9,851). Hazard ratios (HRs) for incident CVD events (coronary heart disease [CHD] and ischemic strokes) were calculated using a Cox proportional-hazards model.
Results:
Lp(a) levels were higher with wider interindividual variation in African Americans (median [interquartile range]: 12.8 [7.1-21.7] mg/dl) than Caucasians (4.3 [1.7-9.5] mg/dl; p < 0.0001). At 20 years of follow-up, 676 CVD events occurred in African Americans and 1,821 events occurred in Caucasians. Adjusted hazard ratios (HRs) (95% confidence interval [CI]) per race-specific 1-standard deviation–greater log-transformed Lp(a) were 1.13 (1.04-1.23) for incident CVD, 1.11 (1.00-1.22) for incident CHD, and 1.21 (1.06-1.39) for ischemic strokes in African Americans. For Caucasians, the respective HRs (95% CIs) were 1.09 (1.04-1.15), 1.10 (1.05-1.16), and 1.07 (0.97-1.19). Quintile analyses showed that risk for incident CVD was graded but statistically significant only for the highest compared with the lowest quintile (HR [95% CI] 1.35 [1.06-1.74] for African Americans; HR 1.27 [1.10-1.47] for Caucasians). Similar results were obtained using Lp(a) cut-offs of ≤10 mg/dl, >10-≤20 mg/dl, >20-≤30 mg/dl, and >30 mg/dl.
Conclusions:
The authors concluded that Lp(a) levels were positively associated with CVD events, and the associations were at least as strong in African Americans as compared with Caucasians.
Perspective:
In this large population-based study of African Americans and Caucasians followed for up to 20 years, Lp(a) levels were positively associated with risk for incident CVD events in both races. Furthermore, the strength of association for incident CVD events was equivalent for African Americans and Caucasians. This analysis extends the previously observed associations between small apo(a) isoforms and CVD events to show that total Lp(a) levels were also associated with incident CVD events in African Americans. Elevated Lp(a) levels should therefore be considered a risk factor for CVD in African Americans.
Keywords: Coronary Artery Disease, Atherosclerosis, Proportional Hazards Models, Lipoprotein(a), Biomarkers, Cardiovascular Diseases
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