Elevated Lipoprotein(a) and Risk of Ischemic Stroke

BACKGROUND High lipoprotein(a) is associated with increased risk of myocardial infarction and aortic valve stenosis. Previous studies have examined the association of lipoprotein(a) and risk of stroke; however, the results are conflicting. OBJECTIVES The purpose of this study was to test if high lipoprotein(a) is associated with high risk of ischemic stroke observationally and causally from human genetics. METHODS The study included 49,699 individuals from the Copenhagen General Population Study and 10,813 individuals from the Copenhagen City Heart Study with measurements of plasma lipoprotein(a), LPA kringle-IV type 2 number of repeats, and LPA rs10455872. The endpoint of ischemic stroke was ascertained from Danish national health registries and validated by medical doctors. RESULTS Compared with individuals with lipoprotein(a) levels 93mg/dl (>199 nmol/L: 96th to 100th percentile). In observational analyses for a 50 mg/dl (105 nmol/l) higher lipoprotein(a) level the age- and sex-adjusted hazard ratio for ischemic stroke was 1.20 (95% CI: 1.13 to 1.28), while the corresponding age- and sex-adjusted genetic causal risk ratio for KIV-2 number of repeats was 1.20 (95% CI: 1.02 to 1.43) and for rs10455872 was 1.27 (95% CI: 1.06 to 1.51). The highest absolute 10-year risk of ischemic stroke was 17% in active smoking individuals >70 years of age with hypertension and lipoprotein(a) levels >93 mg/dl (>199 nmol/l: 96th to 100th percentile). In the Copenhagen City Heart Study, risk estimates for high levels of lipoprotein(a) were in the same direction but did not reach statistical significance. CONCLUSIONS In a large contemporary general population study, high plasma levels of lipoprotein(a) were associated with increased risk of ischemic stroke both observationally and causally from human genetics.