Which of the following is a common risk factor for heart disease?

Smoking is a well-established common risk factor for heart disease. It contributes to the development of atherosclerosis, where plaque builds up in the arteries, leading to reduced blood flow and increasing the chances of heart attacks and strokes. The chemicals in cigarettes can damage blood vessels and heart tissue, raise blood pressure, and lead to an increased heart rate. Quitting smoking is one of the most effective ways to reduce the risk of heart disease and improve overall cardiovascular health.

In contrast, a low cholesterol diet typically aims to decrease the intake of saturated fats and cholesterol, thereby potentially lowering one's risk for heart disease. Regular physical activity and high levels of physical fitness are both protective factors, contributing positively to heart health by improving circulation, lowering blood pressure, and maintaining healthy weight levels.