Cancer isn't the only health risk caused by long-term smoking. Smoking increases your risk of heart attack, stroke, and chronic respiratory conditions like asthma, bronchitis and emphysema. When a person smokes, oxygen in the blood is replaced by carbon monoxide, the blood vessels narrow, and nicotine increases the heart and blood pressure. To make sure enough oxygen is distributed throughout the body, the heart has to pump harder in order to compensate. Eventually, this causes strain on the heart, which causes the heart disease associated with smoking. Respiratory diseases result from inhaled carbon monoxide and tar from cigarettes.
Luckily for smokers who decide to quit, the health of the body improves very quickly after a person stops smoking. The blood pressure and pulse can be back to normal about an hour after a cigarette, and carbon monoxide will be out of the body in a few days. After a month, coughing and shortness of breath will improve. After only a year, an ex-smoker's risk of heart disease goes down by 50 percent. After 15 years, a former smoker has no increased risk of heart attack from smoking [source: University of South Florida].