Doctor, My Cholesterol Levels Are Good. Why are You Starting a Statin?

I get this question frequently from patients.
It is a reasonable question. If statins are a treatment for abnormally high cholesterol levels why would we start them on a patient with normal or low levels.
The answer is that we are not concerned with cholesterol levels. What we are concerned with is atherosclerotic cardiovascular disease (ASCVD) and its downstream consequences including heart attack and stroke.
Thus, the new guidelines recommend  calculating a patient’s 10 year risk of heart attack and stroke due to ASCVD ( see here for my discussion of smart phone app that makes this calculation) and if it is over 7.5% to consider starting a statin drug to reduce ASCVD risk.
Cholesterol is just one of many factors that effect the risk but we know that irrespective of cholesterol level, starting a statin will substantially lower the risk.
A patient  who has smoked   cigarettes lifelong  asked me this question recently.
When I plugged the patient’s excellent cholesterol values into the ASCVD app, the 10 year risk of heart attack or stroke was quite high, 14.9%. Bad cholesterol  (LDL) was 90, well below what is considered optimal. Good cholesterol (HDL) was 60, well above what is considered optimal.
Studies have demonstrated that even patients with cholesterol numbers this good benefit from statin therapy. Their risk of heart attack and stroke will be substantially reduced over time.
My patient has not yet had a heart attack or stroke and it is likely that despite engaging in the extremely damaging behavior of cigarette smoking , the genetically programmed excellent cholesterol values have somewhat protected from ASCVD.
However, a vascular screening study has demonstrated  that  early atherosclerotic plaque in both the patients carotids. The patient has ASCVD and it is only a matter of time if the patient keeps smoking before the patient  has a clinical event related to it.
I told my patient that if he/she stopped smoking cigarettes his/her estimated 10 year risk would drop to 9.7% and I would not recommend statin therapy.
We discussed methods to help quit and the patient indicated that the patient would start  using a nicotine patch and try to quit in the next few months.
Unfortunately, at follow up smoking was ongoing.
Thus, my recommendation to start statin therapy despite her excellent cholesterol values.
Other groups of patients besides cigarette smokers can have advanced or premature ASCVD with excellent or “normal” cholesterol values. Diabetics often have low bad cholesterol values associated with low good cholesterol and high triglycerides.
Sometimes, ASCVD develops prematurely even in patients who have a low 10 year risk based on standard risk factors. This is usually in patients with a strong family history of ASCVD who have an inherited atherogenic abnormality of lipid metabolism that is not manifested in the standard cholesterol parameters (see Dealing With the Cardiovascular Cards You’ve Been Dealt).
To identify these patients a search for subclinical atherosclerosis by vascular screening or coronary calcium scan is necessary. When advanced plaque is identified statin therapy is often warranted even with a low estimated 10 year risk and normal cholesterol values.
So some patients can have very high cholesterol values and I don’t recommend any therapy, some have low and I do. I’m much more focused on the presence or absence of ASCVD in my treatment decisions.
Ultimately we are not treating “high cholesterol” when we start cholesterol lowering therapy we are working to prevent or slow the progression of ASCVD,
-atherosclerosis is still my psychosis
-ACP