Distribution of LDL-Cholesterol Levels and Their Associations With Cardiovascular Outcomes in Young Adults Under 40 Years in South Korea: A Nationwide Cohort Study.

OBJECTIVE

We examined the distribution of low-density lipoprotein cholesterol (LDL-C) levels and compared the hazards of myocardial infarction (MI), stroke, and their composite according to LDL-C concentration in young adults.

METHODS

This was a nationwide, population-based study. From the Korean National Health Insurance Service database (2002-2022), we identified adults aged 20-39 years without prior MI or stroke who underwent at least 1 health examination between 2009 and 2012 (n=6,458,006). The hazards of MI, stroke, and their composite were evaluated across LDL-C levels.

RESULTS

During a median follow-up of 12.6 years, 47,107 MIs, 28,536 strokes, and 73,897 composite events occurred. The hazard of outcomes showed a J-shaped association with LDL-C levels, with the lowest hazard observed around 90-110 mg/dL. Above this range, the hazard increased progressively with rising LDL-C levels. In analyses based on LDL-C categories, levels ≥130 mg/dL were associated with significantly increased hazards of outcomes, with the highest hazards observed at ≥160 mg/dL. The elevated hazards in the higher LDL-C categories were more pronounced in individuals with abdominal obesity and current smokers for all 3 outcomes, and in those with higher body mass index categories, low high-density lipoprotein-cholesterol, and hypertriglyceridemia for MI and the composite outcome.

CONCLUSION

Among young adults, cardiovascular risk demonstrated a J-shaped association with LDL-C levels. Risks increased progressively beyond approximately 90-110 mg/dL, especially in the presence of other cardiometabolic risk factors. These findings underscore the importance of lipid monitoring and cardiovascular risk assessment even in young adults, particularly those with concurrent risk factors.