J-shaped association between LDL cholesterol and cardiovascular events: A longitudinal primary prevention cohort of over 2.4 million people nationwide

Introduction: Low-density lipoprotein (LDL) cholesterol-lowering treatment is beneficial for the secondary or primary prevention of high-risk atherosclerotic cardiovascular disease (ASCVD). However, the prognostic implications of low LDL cholesterol levels in patients without previous ASCVD and without statin use remain elusive. Methods: From a nationwide cohort, 2,432,471 participants without previous ASCVD or statin use were included. For myocardial infarction (MI) and ischemic stroke (IS), participants were followed-up from 2009 to 2018. They were stratified according to 10-year ASCVD risk (<5 %, 5 %–<7.5 %, 7.5 %–<20 %, and ≥20 %) and LDL cholesterol level (<70, 70–99, 100–129, 130–159, 160–189, and ≥190 mg/dL). Results: The relationship between LDL cholesterol levels and ASCVD events exhibited a J-shaped curve for both MI and IS. After classification according to the ASCVD risk, this J-shaped relationship was consistently observed for the composite of MI and IS. Participants with an LDL cholesterol level <70 mg/dL showed a higher MI risk than those with a level of 70–99 mg/dL or 100–129 mg/dL in the low-ASCVD risk group. The J-shaped curve between LDL cholesterol levels and MI risk was attenuated across ASCVD risk groups. For IS, participants with an LDL cholesterol level <70 mg/dL demonstrated increased risks compared with those with a level of 70–99 mg/dL, 100–129 mg/dL, or 130–159 mg/dL in the borderline, intermediate, and high ASCVD risk groups, respectively. In contrast, a linear association was observed in participants taking statins. Interestingly, a J-shaped association was observed between LDL cholesterol and high-sensitivity C-reactive protein (hs-CRP) levels; the mean hs-CRP level and the proportion of individuals with increased hs-CRP levels were relatively high among individuals with an LDL cholesterol level <70 mg/dL. Conclusions: Although high LDL cholesterol levels increase the risk of ASCVD, low LDL cholesterol levels do not warrant safety from ASCVD. Therefore, individuals with low LDL cholesterol levels should be carefully monitored.