The Connection Between Smoking and Heart Disease
Much has been written about the link between smoking and a host of medical problems, including emphysema and other respiratory illnesses, to cancers and cardiovascular diseases. The causal relationship between smoking and a respiratory disease may seem logical to many. After all, tobacco smoke has direct contact with the smoker's mouth, esophagus and lungs. Why, though, are smokers also at increased risk for coronary heart disease (CHD), hypertension and stroke?
A historical perspective
Since the beginning of the last century, there has been some suspicion of a possible link between smoking and heart disease. In 1904, studies found smokers had a higher incidence of intermittent claudication (pain in the calf due to temporary artery narrowing) than nonsmokers. By 1934, research indicated an increase in CHD since World War I and suggested that it correlated with increased smoking in the United States. Four years later, an epidemiologic study suggested shortened life duration as a result of cigarette smoking.
The medical community, however, took little heed of these early warnings, for the initial studies were sporadic and in sharp contrast to the general acceptance and widespread popularity of smoking.
Critical thinking regarding smoking only began to take shape in the late 1940s and early 1950s when research began to link tobacco use with lung cancer. When Reader's Digest printed "Cancer by the Carton" in 1952, there was immediate, widespread concern. To counter a significant drop in sales, cigarette companies increased advertising and promoted the relatively new filter-tip cigarette. These new cigarettes allayed consumer's fears about cancer, and cigarette smoking was again on the rise.
By 1956, the Surgeon General established its first scientific study group to analyze the health effects of smoking, and in 1962 established an advisory panel to completely assess data and make formal recommendations. To many, the subsequent Surgeon General's Report of 1964 was a turning point in the medical community's and public's perception of smoking.
Why smoking contributes to heart disease?
If cigarette warning labels listed all of the compounds in cigarette smoke the way food labels list ingredients, the packaging would read like a chemistry mid-term. Reported for the first time in 1964, and confirmed and expanded upon in following Surgeon General Reports, cigarettes consist of ingredients that when heated create a smoking material comprised of more than 4,000 compounds.
Among these components are 43 different cancer-causing substances and thousands of others that fall under categories such as mutagenic (capable of causing a gene change), pharmacologically active (acting as a drug) and toxic (likely to act as a poison). Many of these gaseous compounds alter as the temperature of the burning cigarette rises and falls with inhalation. A strong dose-related association exists between cigarette usage and CHD.
Evidence also indicates that such damage diminishes when you quit smoking. The two most commonly cited culprits in cigarette smoke are nicotine and carbon monoxide.
What nicotine does to your body?
Nicotine, best known as the addictive agent in cigarettes, is readily absorbed through tiny air sacs in the lungs and is metabolized primarily in the liver. Its impact on the body is profound, for it promotes atherosclerosis; triggers coronary thrombosis (blood clots), coronary artery spasm, and cardiac arrhythmia; and reduces the blood's capacity to deliver oxygen.
Atherosclerosis, or the build-up of fatty substances or plaque in the inner lining of the artery, is promoted and accelerated by nicotine through several mechanisms. Nicotine damages the endothelium, or cells lining the blood vessels. It also causes proliferation of smooth muscle in atherosclerotic lesions (areas of abnormal tissue change) that increases the adherence of platelets to the lining of the blood vessels.
Nicotine in the bloodstream also lowers one's threshold for ventricular fibrillation, the most serious cardiac rhythm disturbance. And smokers' levels of high-density lipoprotein-cholesterol, often referred to as the "good" cholesterol, are decreased in response to the presence of nicotine. Smokers are 20 times more likely to experience a vasospasm, also known as a coronary artery spasm, due to nicotine. Simultaneously, nicotine and other components of cigarette smoke acutely increase blood pressure and heart rate.
When heated, materials in a cigarette convert to numerous gaseous agents, among them, carbon monoxide. Carbon monoxide reduces the amount of oxygen carried by the red blood cells, which consequently reduces oxygen in the tissues. Additional harmful components of cigarette smoke include hydrogen cyanide, nitrogen oxides, carbon disulfide, cadmium, zinc and tar, among others.
The overall effect of cigarettes on the cardiovascular system is to increase general wear and tear while compromising the body's usual ability to function under duress. Smoking acts in combination with the other major risk factors – high blood pressure, high cholesterol, physical inactivity, obesity and diabetes – to compromise the body's cardiovascular health. It accounts for more than 430,000 deaths annually and is completely preventable.
Quitting smoking can improve your health and quality of life. Reducing the number of cigarettes you smoke is also beneficial, but cutting down on the amount of nicotine in your cigarettes will not provide any benefit if you smoke a greater number of cigarettes. Ask your health care professional to help determine which type of cessation method will work best for you.