People with higher levels of 'bad' cholesterol in their blood are more likely to have heart attacks or other heart problems.

When you have too much 'bad' cholesterol (LDL) in your blood, it sticks to the walls of your arteries and builds up like gunk, making them narrow and stiff — which raises your chance of having a heart attack or stroke.

High cholesterol might not be the main reason for heart disease, and having too little cholesterol could actually be risky — so the old idea that cholesterol causes heart problems might not tell the whole story, especially for preventing heart issues in healthy people.

In 2009, the 'bad' cholesterol levels in white American adults were about 7% lower than they were in 2000, which could mean less risk for heart disease — but other factors might have contributed too.

If you're a middle-aged person with symptoms, having higher 'bad' cholesterol (LDL) means you're more likely to have heart problems over the next four years — but only if scans show you already have plaque in your heart arteries.

If your 'bad' cholesterol is 100 or higher, lowering it more aggressively helps prevent heart-related deaths. But if it's already below 100, lowering it even more doesn't seem to help much — there might be a cutoff where treatment stops adding extra benefit.