Atherosclerosis refers to a progressive narrowing of the arteries due to atheroma, derived from the Greek word for gruel or porridge. Atheromatous plaque is a mixture of fat and inflammatory debris that sticks to the inner walls of an artery. Plaque can be soft or become firm as it accrues layers of calcium, a byproduct of chronic inflammation. Atherosclerosis has no single cause but many recognized risk factors. Some risk factors are modifiable, and others are not. Age and genetic predispositions are an example of "non-modifiable" risk factors. Medical management of atherosclerosis aims to address the many other known "modifiable" risk factors, such as smoking, diet, exercise as well as blood sugar levels in patients with diabetes. Using medications to control blood pressure and cholesterol have also been shown beneficial.