> Nobody is going to think mortality causes high cholesterol. Prevalent cardiovascular disease, or having a high risk for cardiovascular disease, causes low ch

> Nobody is going to think mortality causes high cholesterol. Prevalent cardiovascular disease, or having a high risk for cardiovascular disease, causes low cholesterol. It does so by your doctor recognizing your elevated risk and putting you on statins. Statins, like all drugs for prevention, do not prevent all subsequent disease. Perhaps most importantly, they only reduce cholesterol from the time you start taking them (as opposed to a genetically-driven low cholesterol throughout life). All of the drugs for chronic disease prevention tend to have a pretty small effect on the disease risk. Therefore, detecting that someone is taking a statin is a great signal that the person is at high risk for disease. They would be at an even higher risk if they weren't on a statin, but the statin does not erase all risk. That is why failing to account for statin use will lead to low cholesterol looking protective, if there are people in the population taking statins.