CONTEXT: Novel, low-density lipoprotein (LDL) cholesterol-lowering proprotein convertase subtilisin/kexin type-9 (PCSK9) inhibitors also lower lipoprotein(a) levels, but the effect on aortic valve stenosis and myocardial infarction is unknown.

OBJECTIVE: We tested the hypothesis that the PCSK9 R46L loss-of-function mutation is associated with lower levels of lipoprotein(a) and with reduced risk of aortic valve stenosis and myocardial infarction.

DESIGN: We used two prospective cohort studies of the general population and one patient-based cohort.

SETTING: Cohort studies selected at random individuals of Danish descent.

PARTICIPANTS: We studied 103 083 individuals from the Copenhagen General Population Study, the Copenhagen City Heart Study, and the Copenhagen Ischemic Heart Disease Study.

MAIN OUTCOME MEASURES: Lipoprotein(a), LDL cholesterol, and PCSK9 R46L genotype and diagnoses of aortic valve stenosis and myocardial infarction from national registries; lipoprotein(a) was measured from 49,617 individuals.

RESULTS: Median (interquartile range) lipoprotein(a) levels were 10 (5-30) mg/dl for PCSK9 R46L noncarriers, 9 (4-32) mg/dl for heterozygotes, and 8 (4-42) mg/dl for homozygotes (trend P = .02). The corresponding values for LDL cholesterol levels were 124 (101-147) mg/dl, 104 (85-132) mg/dl, and 97 (85-128) mg/dl, respectively (trend P = 2 × 10(-52)). PCSK9 R46L carriers vs noncarriers had an age- and sex-adjusted odds ratio of 0.64 (95% confidence interval, 0.44-0.95) for aortic valve stenosis, 0.77 (0.65-0.92) for myocardial infarction, and 0.76 (0.64-0.89) for aortic valve stenosis or myocardial infarction.

CONCLUSIONS: PCSK9 R46L carriers have lower levels of lipoprotein(a) and LDL cholesterol as well as reduced risk of aortic valve stenosis and myocardial infarction. This indirectly suggests that PCSK9 inhibitors may have a role in patients with aortic valve stenosis.