*Geek Box: Blood Lipid Levels
Context will be helpful in any study you read with blood cholesterol levels as an outcome, so let’s expand on this here. We now have overwhelming proof that LDL-C causes atherosclerosis. Now, this doesn’t mean that other lipoproteins are not a risk factor, it just means they have not yet satisfied the scientific criteria for causality. But they are close; for example, lipoprotein(a), or Lp(a), has an intervention trial beginning which is directly targeting Lp(a) reductions, and if that is successful, Lp(a) will also be deemed causal. However, LDL-C remains the prime focus for now, and is the main focus of treatment guidelines.
Current guidelines indicate that normal LDL-C is <116mg/dL or <3.0mmol/L, but in people with no other health issues, an LDL-C of up to 130mg/dL or 3.3mmol/L is not currently considered a major concern. This is, however, an ongoing conversation as the evidence for ‘lower is better and earlier is better’ continues to get stronger. For people at moderate cardiovascular risk, the goal is LDL-C <100mg/dL or <2.6mmol/L. For high risk, the goal is a reduction of >50% from baseline, aiming for LDL-C <70mg/dL or <1.8mmol/L. Very high-risk in primary prevention [i.e., have not suffered a cardiovascular event yet], the goal is LDL-C <55mg/dL or <1.4mmol/L. The goals for secondary prevention the goals are the same as very-high risk primary prevention, however, if a second event occurs, the goal is LDL-C <40mg/dL or <1.0mmol/L.
It is helpful reading papers to have these latest treatment guidelines from the European Atherosclerosis Society in mind. And, if a paper ever reports in either mg/dL or mmol/L, and you understand one or the other better, then to convert mg into mmol, divide by 38.6; to convert mmol into mg, multiple by 38.6.