Explain cigrates smoking from lifestyle risk factors ?

Smoking is the single most important preventable risk factor for CAD. There is strong evidence that smoking can significantly increase CAD morbidity and mortality, an adverse effect, which is related to the amount of tobacco smoked daily and the duration of smoking. Approximately 50-150 microgram of nicotine is absorbed through the lung with each puff of smoke. Nicotine is a potent agonist of sympathetic nervous system and causes release of nor-epinephrine which in turn increases coronary tone and provokes vasoconstriction.
Many studies have shown that smokers have approximately twice the risk of CAD as non-smokers. Smoking causes endothelial injury, increases heart rate and blood pressure, decreases oxygen level in the blood because of production of carbon monoxide lowers HDL cholesterol, causes coronary spasm, increases platelet aggregation and promotes blood clotting - all of which aggravates the atherosclerotic and ischemic process. Passive smoking or so-called 'second-hand' smoking has also been found to increase CAD risk, Non-smokers exposed to cigarette smoke have increased risk of Cardio-vascular diseases. Different forms of non-smoke tobacco are also harmful.
Smoking cessation is rapidly followed by a significant decrease in Cardio-vascular morbidity and mortality. The benefits of smoking cessation are seen regardless of how long and how much the patient previously smoked.