Smoking or using tobacco is one of the most significant risk factors for developing heart disease. Chemicals in tobacco can damage your heart and blood vessels, leading to narrowing of the arteries (atherosclerosis). Atherosclerosis can ultimately lead to a heart attack. When it comes to heart disease prevention, no amount of smoking is safe. Smokeless tobacco and low-tar and low-nicotine cigarettes also are risky, as is exposure to secondhand smoke. In addition, the nicotine in cigarette smoke makes your heart work harder by narrowing your blood vessels and increasing your heart rate and blood pressure. Carbon monoxide in cigarette smoke replaces some of the oxygen in your blood. This increases your blood pressure by forcing your heart to work harder to supply enough oxygen. Even so-called "social smoking" smoking only while at a bar or restaurant with friends is dangerous and increases the risk of heart disease. Women who smoke and take birth control pills are at greater risk of having a heart attack or stroke than are those who don't do either. This risk increases with age, especially in women older than 35. The good news, though, is that when you quit smoking, your risk of heart disease drops dramatically within just one year. And no matter how long or how much you smoked, you'll start reaping rewards as soon as you quit. (This topic is copy pasted)