Variability in Lipid Profiles During Young Adulthood and the Risk of Coronary Artery Calcium Incidence in Midlife: Insights From the CARDIA Study.

BACKGROUND Intraindividual variability in lipid profiles is recognized as a potential predictor of cardiovascular events. However, the influence of early adulthood lipid profile variability along with mean lipid levels on future coronary artery calcium (CAC) incidence remains unclear. METHODS A total of 2395 participants (41.6% men; mean±SD age, 40.2±3.6 years) with initial CAC =0 from the CARDIA study (Coronary Artery Risk Development in Young Adults) were included. Serial lipid measurements were obtained to calculate mean levels and variability of total cholesterol, low-density lipoprotein cholesterol (LDL-C), non-high-density lipoprotein cholesterol (non-HDL-C), and triglycerides. CAC incidence was defined as CAC >0 at follow-up. RESULTS During a mean follow-up of 9.0 years, 534 individuals (22.3%) exhibited CAC incidence. Higher mean levels of total cholesterol, LDL-C, and non-HDL-C were associated with a greater risk of future CAC incidence. Similarly, 1-SD increment of lipid variability, as assessed by variability independent of the mean, was associated with an increased risk of CAC incidence (LDL-C: hazard ratio, 1.139 [95% CI, 1.048-1.238]; P=0.002; non-HDL-C: hazard ratio, 1.102 [95% CI, 1.014-1.198]; P=0.022; and triglycerides: hazard ratio, 1.480 [95% CI, 1.384-1.582]; P<0.001). Combination analyses demonstrated that participants with both high lipid levels and high variability in lipid profiles (LDL-C and non-HDL-C) faced the greatest risk of CAC incidence. Specifically, elevated variability of LDL-C was associated with an additional risk of CAC incidence even in low mean levels of LDL-C (hazard ratio, 1.396 [95% CI, 1.106-1.763]; P=0.005). These findings remained robust across a series of sensitivity and subgroup analyses. CONCLUSIONS Elevated variability in LDL-C and non-HDL-C during young adulthood was associated with an increased risk of CAC incidence in midlife, especially among those with high mean levels of atherogenic lipoproteins. These findings highlight the importance of maintaining consistently low levels of atherogenic lipids throughout early adulthood to reduce subclinical atherosclerosis in midlife. REGISTRATION URL: https://www.clinicaltrials.gov; Unique identifier: NCT00005130.