Americans LDL cholesterol levels have stopped dropping-and no one knows why. A new study published in PLoS One reports that average levels of the bad cho-lesterol declined from 120 milligrams per deciliter in 2001 to 104.7 in 2008 (less than 100 is optimal). But since then the improve-ment has stopped, with 2011 levels averaging an almost unchanged 104.3. The study used data from a medical testing company on blood LDL levels of almost 105 million adults. Weve raised a red flag that something dra-matic happened, said the researchers, who offered three theories: The recession may have made patients cut back on doctor visits and cholesterol-lowering statin drugs; the benefits of taking those medications could have plateaued; or increases in obesity might have begun to overwhelm statins benefits.