LDL Cholesterol (LDL-C)

LDL cholesterol (LDL-C) measures the cholesterol carried by low-density lipoprotein particles, the primary carrier historically blamed for depositing cholesterol in artery walls and driving atherosclerosis. The claim: decades of genetic, epidemiological, and interventional evidence converge on LDL-C, or more precisely the particle count it approximates, as a causal driver of cardiovascular disease, not merely a correlated marker.

A 2024 systematic review and meta-analysis of Mendelian randomization studies, using genetic variants as natural experiments that avoid confounding, pooled 5,828,409 participants across 21 records and found a significant causal association between LDL and coronary artery disease (odds ratio 1.37, 95% CI 1.26-1.49, p<0.001) [1]. This genetic evidence complements decades of statin, ezetimibe, and PCSK9-inhibitor randomized trials showing that lowering LDL-C reduces cardiovascular events roughly in proportion to the absolute LDL-C reduction achieved, a dose-response relationship the Cholesterol Treatment Trialists' Collaboration has documented across more than 20 major trials [2].

How to measure it: standard lipid panels either calculate LDL-C using the Friedewald equation (total cholesterol minus HDL-C minus triglycerides/5) or measure it directly [6]. The Friedewald calculation becomes unreliable when triglycerides exceed roughly 400 mg/dL, understating true LDL-C in people with metabolic syndrome or poorly controlled diabetes, which is one reason some clinicians prefer direct LDL-C measurement or ApoB testing in those patients [3].

How to intervene on it: statins remain the best-studied LDL-lowering intervention, reducing LDL-C by 30-50% depending on dose and reducing major cardiovascular events proportionally in large trials [4]. Ezetimibe adds roughly another 15-20% reduction on top of a statin. PCSK9 inhibitors can lower LDL-C by 50-60% further, with outcome trials (FOURIER, ODYSSEY) confirming proportional event reduction even at very low achieved LDL-C levels, undermining older concerns that LDL-C could be lowered "too much" [4].

Critics, a much smaller group within cardiology, argue that all-cause mortality benefits from statins in primary prevention (people without existing heart disease) are more modest than cardiovascular-event reduction alone would suggest, and that absolute risk reduction matters more than relative risk reduction for shared decision-making with lower-risk patients. Some also argue LDL-C is a flawed proxy for the true causal exposure, meaning particle number best captured by ApoB, since LDL-C and ApoB can be discordant in people with high triglycerides [3]. Bryan Johnson's Blueprint protocol reports LDL-C and ApoB results as part of its public dashboard, an n=1 self-tracking example of the ApoB-alongside-LDL-C approach [5].

The plain takeaway: LDL-C is a well-established causal risk factor for atherosclerotic cardiovascular disease, supported by genetic, epidemiological, and drug-trial evidence that converge on the same conclusion, though people with high triglycerides or metabolic syndrome should consider ApoB testing since LDL-C alone can understate their actual particle-driven risk.