Estimated Small, Dense LDL Cholesterol and Atherosclerotic Cardiovascular Risk in the UK Biobank

BACKGROUND: A key step in primary prevention is the assessment of atherosclerotic cardiovascular disease (ASCVD) risk. Risk enhancer tests are additional tools used to further improve ASCVD risk assessment over conventional risk markers. Our objective was to determine whether estimated small, dense low-density lipoprotein cholesterol (E-sdLDL-C) can improve risk assessment and serve as a new risk enhancer test. METHODS: We used a prospective cohort analysis of participants in the UK Biobank study with a median (interquartile range) follow-up of 10 (6.7–12.3) years. We included 271 760 individuals who were not on lipid-lowering medication at baseline and did not have incident ASCVD. The primary study outcome was the incidence of all-cause ASCVD. RESULTS: E-sdLDL-C was strongly associated with ASCVD events with a hazard ratio (HR) of 1.23 (95% CI, 1.22–1.24). After multivariable adjustment for age, sex, systolic blood pressure, hypertension, type 2 diabetes, and blood pressure medications, E-sdLDL-C and ApoB (apolipoprotein B) remained the most significant lipid risk factors (HR, 1.18 [95% CI, 1.16–1.19] and 1.17 [95% CI, 1.16–1.18] per SD, respectively). After further adjustment for ApoB, the association between low-density lipoprotein cholesterol (LDL-C) with all-cause ASCVD was completely reversed with an HR of 0.84 (95% CI, 0.81–0.86), but E-sdLDL-C continued to have a significant positive association with an HR of 1.11 (95% CI, 1.08–1.13). When E-sdLDL-C was discordantly higher than either LDL-C or ApoB, the risk for ASCVD was higher (LDL-C, 31% higher; ApoB, 17% higher). When elevated E-sdLDL-C is coupled with other risk enhancer tests, there is a greater risk for developing ASCVD. CONCLUSIONS: In a UK Biobank cohort for primary prevention, the risk of all-cause ASCVD was better captured by E-sdLDL-C than LDL-C. It was also more predictive than LDL-C and ApoB when discordant with these 2 measures. E-sdLDL-C, which can be freely and automatically calculated from a standard lipid panel, can potentially improve ASCVD risk assessment without additional laboratory testing.