Heart disease and strokes (cardiovascular disease) are leading causes of death and disability in most western countries. Smoking, high-fat diets, high cholesterol, high blood pressure, diabetes, and kidney disease increase a person's risk for cardiovascular disease. Recently, researchers identified several additional risk factors for cardiovascular disease. These newer risk factors include proteins that are involved in blood clotting and are released in response to inflammation (fibrinogen and C-reactive protein). They also include an amino acid (homocysteine) that may be elevated when intake of vitamins, such as folic acid, is low. How the newer risk factors relate to older, more established risk factors, such as smoking, is not well studied.