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Smoking is the leading cause of preventable death.

Although the addictive properties of nicotine affect almost all smokers, there are also individual differences in smoking behavior, nicotine dependence, and cessation success.

A genetic variant has been found that among smokers, is associated with more smoking and higher rates of nicotine dependence, making it more difficult to quit.

The best and most simple prevention is never to start smoking. For people who have already started to smoke, the best prevention is to quit. Smoking cessation can have immediate health benefits.

Although nicotine dependence develops in all regular smokers, individual differences have been found among smokers that can be attributed to a genetic variant

Cigarette smoking is the leading preventable cause of death worldwide

Smoking is the leading cause of preventable death, causing approximately five million premature deaths world-wide each year. One of every six deaths in the United States can be linked to the smoking of tobacco, making this substance more lethal than all other addictive drugs combined.

Nicotine is the addictive substance in tobacco

Nicotine, a component of tobacco, is the primary reason for its addictiveness. However, cigarette smoke contains many other dangerous chemicals, including tar, carbon monoxide, acetaldehyde, nitrosamines, and more. The inhalation of tar increases the risk of lung cancer, emphysema, and bronchial disorders. Carbon monoxide increases the chance of developing cardiovascular diseases. Additionally, secondhand smoke increases the risk of lung cancer in adults and greatly increases the risk of respiratory illnesses in children.

Why do people continue to smoke?

So why do people smoke? Nicotine addiction is what keeps many people smoking despite its harmful effects. In general, addiction is characterized by the compulsive seeking and use of a particular stimulus, even in the face of negative health consequences. It is well documented that most smokers identify tobacco use as harmful and express a desire to reduce or stop using it. Unfortunately, only about 6 percent of people who try to quit are successful for more than a month.

A genetic variant affects how much smokers smoke and how dependent they become

Although the addictive properties of nicotine affect almost all smokers, there are also individual differences in smoking behavior, nicotine dependence, and cessation success. Some of these individual differences have been attributed to genetic factors, prompting a search for susceptibility genes. Recently scientists at deCODE genetics discovered an association between Nicotine Dependence and a specific variant in the genome. The variant is located on chromosome 15 within the nicotinic acetylcholine receptor gene cluster. The variant does not seem to influence the likelihood of whether people start to smoke or not, but among smokers, carriers of the genetic variant smoke more than non-carriers and have higher rates of nicotine dependence, making it more difficult for them to quit. In smokers, this same variant also increases the risk for Lung Cancer and Peripheral Arterial Disease.

deCODEme calculates your genetic risk of nicotine dependence

The deCODEme Complete Scan identifies the risk variant rs1051730 on chromosome 15 and associated with increased risk of nicotine dependence and uses it to provide customers with a personalized interpretation of their genetic risk for developing nicotine dependence. Since the genetic variant has not been associated with the initiation of smoking, the associated risk applies only to those individuals who are or have been smokers.

risk factors

Smoking harms every organ in the body

Although many associate smoking first and foremost with lung cancer and lung diseases, smoking harms every organ in the body. Cigarette smoking has been linked to about 90% of all lung cancer cases, the number-one terminal cancer in both men and women. Smoking is thought to account for about one-third of all cancer deaths.The overall rate of death from cancer is twice as high for smokers compared to nonsmokers, with heavy smokers having a rate four times greater than nonsmokers. Smoking is also associated with cancers of the mouth, pharynx, larynx, esophagus, stomach, pancreas, cervix, kidney, ureter, and bladder.

Smoking also causes lung diseases such as chronic bronchitis and emphysema, and has been found to exacerbate asthma symptoms in adults and children. More than 90% of all deaths from chronic obstructive pulmonary diseases are attributable to cigarette smoking. It has also been well documented that smoking substantially increases the risk of heart disease, including stroke, heart attack, vascular disease, and aneurysms. It is estimated that smoking accounts for approximately 21% of deaths from coronary heart disease each year.

Additionally, secondary smoke increases the risk for many diseases. It is estimated to cause approximately 3,000 lung cancer deaths per year among nonsmokers and contributes to more than 35,000 deaths related to cardiovascular disease. Exposure to tobacco smoke in the home is also a risk factor for starting to smoke and increased severity of childhood asthma and has been associated with sudden infant death syndrome.

prevention and treatment

Quitting smoking results in immediate health benefits for smokers and non-smokers

The best and most simple prevention is never to start smoking. For people who have already started to smoke, the best prevention is to quit.

Smoking cessation can have immediate health benefits. For example, within 24 hours of quitting, blood pressure and chances of heart attack decrease. Long-term benefits of smoking cessation include decreased risk of stroke, lung and other cancers, and coronary heart disease. A 35-year-old man who quits smoking will, on average, increase his life expectancy by 5.1 years.

Most adult smokers want to quit smoking

Research has shown that most adult smokers want to quit smoking (see for example a recent U.S. Gallup poll here). Although some smokers can quit without help, many individuals need assistance in quitting. The following treatments are available to help people quit:

• Nicotine replacement therapies such as nicotine gum and the transdermal nicotine patch are used (often with behavioral support) to relieve withdrawal symptoms and thereby reduce the discomfort associated with quitting. These treatments provide users with lower overall nicotine levels than they receive with tobacco, hence they do not produce the pleasurable effects of smoking, nor do they contain the carcinogens and gases associated with tobacco smoke.
• Non-nicotine medications, such as the antidepressant bupropion has been shown to help people quit smoking. A more recently approved medication is varenicline, which acts at the sites in the brain affected by nicotine and may help people quit by easing withdrawal symptoms and blocking the effects of nicotine if people resume smoking. Several other non-nicotine medications are being investigated for the treatment of tobacco addiction.
• Behavioral support has been shown to enhance the effectiveness of other treatments and improve long-term outcomes. It includes a variety of methods to assist smokers in quitting, ranging from self-help materials to individual cognitive-behavioral therapy.

New smoking cessation treatments are on the horizon

Scientists are also investigating a new nicotine vaccine, designed to stimulate the production of antibodies that would block access of nicotine to the brain and prevent nicotine&rquote;s reinforcing effects.

more information

You can find out more information about nicotine dependence and smoking by talking to your doctor and visiting these Web sites:

• Centers for Disease Control and Prevention on Smoking and Nicotine Dependence
• Mayo Clinic article on Nicotine Dependence
• Mayo Clinic Nicotine Dependence Center
• MedlinePlus article on Smoking
• Society for Research on Nicotine and Tobacco
• U.S. Department of Health & Human Services on Smoking Cessation
• Drug Information -Up-to-date information on prescription and over-the-counter medications
• Drug Side Effects -Gets the latest consumer alerts about medication side effects

scientific references

• Thorgeirsson Th. et al. Nature 2008 April 3. A variant associated with nicotine dependence, lung cancer and peripheral arterial disease. Nature 452, 638-642 (3 April 2008)

This content was last reviewed on February 08, 2010.

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