DescriptionAn in-depth report on the health risks of smoking and how to quit.
Alternative NamesNicotine Replacement
Tobacco, mostly cigarette smoking, kills more than 440,000 people a year, making it more lethal than AIDS, automobile accidents, homicides, suicides, drug overdoses, and fires combined. Indeed, one in every five deaths is attributable to smoking. It reduces life expectancy by 15 to 25 years and is the single most preventable cause of death. In one study, only 42% of male lifelong smokers reached the age of 73, compared to 78% of nonsmokers. Smoking may be even more dangerous in women. Smoking may be even more dangerous now than 30 years ago, most likely because the lower tar and nicotine levels in most cigarette brands cause people to inhale more deeply.
Even cutting back smoking by more than half does not cut the risk for poor health compared to heavy smokers (considered to be more than 15 cigarettes a day). Only quitting helps.
Harmful Chemicals in Cigarette Smoking. The smoke is the most dangerous component of the cigarette. Smoke contains nitrogen oxide and carbon monoxide, which are harmful gases. When people inhale they also bring tar into their lungs. Tar itself includes 4,000 chemicals, some of which are known to cause cancer. Other inhaled chemicals include:
Experts warn that so-called safer cigarettes (e.g., Advance, Omni), which claim to filter out some of these toxins, are still not safe, as the smoke from these cigarettes still contain many harmful chemicals. Even worse, a 2002 study suggested that people who smoke as few as three standard brand cigarettes a day are at higher risk for blood vessel abnormalities that endanger the heart.
Cigars and Pipes. One study reported that people who switch from cigarettes to cigars or pipes halve their risk of lung cancer, heart disease, and chronic lung disease, possibly because they use less tobacco and inhale less. Still, the risk of these diseases using "safer" forms of tobacco is 50% to almost 70% higher than nonsmokers. And the risk for periodontal disease and tooth loss may be just as high in pipe and cigar smokers as it is in cigarette smokers.
Effects of Second-Hand Smoke
The effects of second-hand smoke, or passive smoking, has been debated and widely studied, but they are still not entirely clear. Major organizations, including the American Heart Association and US Surgeon General have stated that passive smoke poses a 30% increase in the risk of heart disease. One analysis of studies suggested that exposure to second-hand tobacco smoke may increase the risk of lung cancer in the nonsmoker by about 25%. The Environmental Protection Agency has classified second-hand smoke as a carcinogen.
Nevertheless, there is some evidence that second-hand smoke may not be as harmful to adults as most people believe. A major 2003 study in California on smokers and their spouses, in fact, found no significant relationship between second-hand smoke and a higher risk for tobacco-related deaths, heart disease, or lung cancer. A 2000 study suggested that the numbers suggesting a high risk for lung cancer from passive smoking may be overstated, because they were derived from many small and possibly biased studies. Some experts believe that studies showing a positive association between poor health and passive smoke may be more likely to be published than negative ones.
Discovering that passive smoking may not be as dangerous as currently believed in adults is not an argument to restore smoking in public areas where it is currently banned. Tobacco smoke is unpleasant for most nonsmokers and any public efforts to discourage smoking in active smokers should be applauded.
Moreover, harmful effects of parental smoking on children have been fairly well established. Smoking in pregnant women and new mothers is strongly linked to low birth weight and sudden infant death syndrome (SIDS). A body of research continues to suggest that exposure to environmental smoke in the home increases a child's risk for lower respiratory tract infections and asthma.
Effects of Smoking and Quitting on Heart Disease, Diabetes and Stroke
Smokers in their thirties and forties have a heart-attack rate that is five times higher than their nonsmoking peers.
Any current smoker is at higher risk for heart disease or stroke. Although heavy smokers--particularly those who smoke high-tar cigarettes--are at highest risk, a 2002 study indicated that even light smokers (as few as three cigarettes a day for women and six for men) doubled their risk of heart attack.
Smoking poses greater risks in women than in men. For example, in women who smoke, the risk for a heart attack is about 50% greater than in male smokers. In women over 35 who smoke, taking oral contraceptives poses special hazards by increasing their risk for heart attack and stroke well beyond their non-smoking peers.
Specific Effects of Smoking on the Heart. Cigarette smoking may be directly responsible for about 62,000 deaths from heart disease each year. Smoking cigars may increase the risk of early death from heart disease, although evidence is much stronger for cigarette smoking. The damaging effects of smoking on the heart are multifold:
Quitting will rapidly reduce the risk of developing heart disease.
Although long-term smoking may still permanently damage arteries, a major 2003 analysis reported that when patients with heart disease quit, their mortality rates were reduced by 36% compared to patients who continued to smoke.
Effects of Smoking on Diabetes. A study of women smokers found that those with type 2 diabetes were at especially high risk for heart disease. Quitting smoking reduced this risk substantially. Smoking may also accelerate other complications of diabetes, including kidney disease.
Effects of Smoking on Stroke. Smoking can affect blood vessels in the brain as it does in the heart. People who smoke a pack a day have almost two and a half times the risk for stroke as nonsmokers. The risk for stroke may remain elevated for as long as 14 years after quitting. Note: women smokers who take oral contraceptives have a specifically higher risk for stroke. In fact, any woman who smokes increases her risk for hemorrhagic stroke, the type of stroke caused by a ruptured blood vessel.
The Effects of Smoking and Quitting on Cancer
Smoking accounts for about 30% of all cancer deaths in the US, and it has been cited as the most important factor in changes in worldwide cancer trends.
Lung Cancer. Smoking is the primary risk factor in 85% to 90% of lung cancers, which is expected to kill nearly 155,000 Americans in 2002. About 15% of all people who smoke develop lung cancer, with the risk varying depending on the duration of the addiction and the number of pack years. (A pack year equals the number of packs of cigarettes smoked per day multiplied by the number of years that the person has smoked.)
The table referred to is from a study of male smokers. Some studies indicate that the risk for lung cancer may be even higher in women smokers. In a 1999 study, the risk for older women was 2.3 times that of older men. Death rates from lung cancer among Caucasian American women increased by 600% between 1950 and 2000, Each year, in fact, lung cancer now kills over 60% more women than breast cancer does and accounts for 25% of all cancer deaths in women.
Some evidence suggests that people who smoke low-tar, or light, cigarettes may be no safer than those who smoke high-tar cigarettes. People who smoke low-tar cigarettes tend to inhale more deeply, bringing particles to the smallest and most vulnerable tissues in the lungs where these cancers start. In fact, these smokers may have a higher risk for a particularly deadly form of lung cancer called adenocarcinoma.
Mentholated cigarettes have also been associated with a higher risk for lung cancer, although a 2003 study failed to find any differences in risk compared to nonmenthol brands.
Other Cancers. Smoking is also related to other cancers:
Biologic Effects of Smoking That May Contribute to Cancer. Cigarette smoke contains many chemicals and cancer may develop from the accumulative effects of more than one.
The Effects of Smoking and Quitting on Acute and Chronic Lung Diseases
Smoking is associated with a higher risk for nearly all major lung diseases, including pneumonia, flu, bronchitis, and emphysema. There is also a link between smoking and exacerbation of asthma symptoms. Second-hand smoke, too, has been associated with respiratory problems, including nighttime chest tightness, breathlessness after exertion, and worsening of asthma.
Quitting almost immediately improves lung function. Some evidence also suggests that benefits for the lungs are even more significant for women who quit than for men. One study indicated that smokers who quit and start again may damage their lungs even more severely than people who have not yet made an attempt to quit. Such people, however, may simply be more strongly addicted than other smokers and may inhale more deeply and hold the smoke in their lungs longer. The message here is not that quitting smoking is more dangerous than not quitting; rather, the emphasis is on not starting again.
Dementia and Neurologic Diseases
The role between smoking and neurologic diseases has been mixed. Nicotine has some positive effects on the brain, including improving concentration and short-term memory. Certainly, smoking can increase the risk for dementia by causing small or major strokes. Low levels of HDL (good cholesterol), which are more common in smokers, have also been linked to dementia.
Parkinson's Disease. Cigarette smokers appear to have a lower risk for Parkinson's disease, indicating some protection by nicotine. This finding, of course, is no excuse to smoke, but such protection may help researchers develop new therapies.
Alzheimer's Disease. Nicotine enhances the actions of the cholinergic system (which is depleted in Alzheimer's disease) and is known to improve concentration and memory in the short term. Some studies have suggested that nicotine may protect nerve cells and help prevent the formation of beta amyloid. One study indicated that nicotine might help protect against Alzheimer's disease in carriers, but not noncarriers, of the ApoE4 gene. Research to date, however, has found no strong evidence of improvement with nicotine replacement methods. Smoking itself makes little difference in the risk for Alzheimer's, and, in fact, the risk for dementia is slightly higher in smokers.
Effect on Male Sexuality and Reproduction
Smoking also negatively affects male sexuality and fertility. Heavy smoking is frequently cited as a contributory factor in impotence in men because it decreases the amount of blood flowing into the penis. One study noted, for example, that among men with high blood pressure, smoking causes a 26-fold increase in impotence.
Smoking also affects fertility. It impairs sperm motility, reduces sperm lifespan, and may cause genetic changes that affect the offspring. One 2002 trial found that men or women who smoke have lower success rates with fertility treatments. An earlier study reported that men who smoke also have lower sex drives and less frequent sex.
The Effects of Maternal Smoking on Fertility, Pregnancy, and Children
Studies have now linked cigarette smoking to many reproductive problems. Women who smoke pose a greater danger not only to their own reproductive health but, if they smoke during pregnancy, to their unborn child. Continuing to smoke also may cause health problems in the growing child.
Female Infertility. Some of the negative effects of smoking on female fertility include the following:
One intriguing study found that mothers or fathers who smoke a pack or more a day are more likely to have daughters than sons. The likelihood of having a male child was lowest when both parents smoked.
Effects on Unborn Child. Smoking during pregnancy is harmful to an unborn child in many ways:
Unfortunately, the standard cessation aids (nicotine replacement, antidepressants) are not appropriate for pregnant women. Women who want to become pregnant should use these aids before they try to conceive and make all attempts to quit.
Effects of Second-Hand Smoke on Children. An estimated four million children a year fall ill from exposure to second-hand smoke. Parental smoking has been shown to affect the lungs of infants as early as the first two to 10 weeks of life, and such abnormal lung function could persist throughout life.
A number of studies have reported associations between smoking parents and childhood illnesses.
If new mothers cannot quit, they should be sure not to smoke in the same room as their infant. This simple behavior can considerably reduce the risks to the child.
Note: Of some encouragement is the fact that in one study, people who had been exposed to tobacco smoke as children did not appear to have any higher risk for lung cancer later on.
Effects on Bones and Joints
Smoking has many harmful effects on bones and joints:
The Effects of Smoking on the Gastrointestinal Tract
Smoking increases acid secretion in the stomach. It also reduces blood flow and production of compounds that protect the stomach lining.
Diverticulitis. A 2000 study suggested that smoking was a major risk factor in diverticulitis, a condition in which small out-pouches develop in the wall of the colon. In addition, smokers were at risk for its complications, including bleeding and abscess. Diverticulitis mostly affects people over 50 years of age.
Inflammatory Bowel Disease. Smoking has mixed effects on inflammatory bowel disease.
Smokers have lower than average rates of ulcerative colitis, but higher than average rates of Crohn's disease. In fact, smokers with Crohn's disease who quit experience a much less severe course.
Peptic Ulcers. Results of studies on the effect of smoking on ulcers are mixed. Some evidence suggests that smoking delays the healing of gastric and duodenal ulcers. One 1999 study reported that after ulcers healed, about half of smokers relapsed after a year and that all heavy smokers relapsed after three months. Other studies, however, have found no increased risk for ulcers in smokers, and smoking does not appear to increase susceptibility to H. pylori, the bacteria that causes many peptic ulcers. This should not give smokers any comfort, however, given the proven dangers from smoking.
Hepatitis and Cirrhosis. Smoking is linked to increased liver scarring (cirrhosis) caused by either excessive drinking or chronic hepatitis B or C viruses.
The Effects of Smoking on the Thyroid and Autoimmune Conditions
Hyper- and Hypothyroidism. Cyanidem, found in tobacco smoke, interferes with thyroid hormone production. Smoking triples the risk for developing thyroid disease, particularly autoimmune hyper- and hypothyroidism. Women smokers with subclinical hypothyroidism, a symptom-free condition in which the thyroid gland is mildly underactive, face an increased risk for developing full-blown hypothyroidism than their nonsmoking peers. Smoking may also increase the negative effects of hypothyroidism on the heart. Smoking has also been linked to goiter, a swelling of the thyroid that occurs in people who dont get enough iodine.
Other Autoimmune Diseases. One study reported that smokers are almost seven times more likely to develop SLE than nonsmokers, and ex-smokers have a 3.6-fold risk, according to research published in 2001. Not all studies support the association.
The Effects of Smoking on Surgical Recovery
Smokers are at increased risk for heart and circulatory problems and delayed wound healing after surgery. In one study, patients who were able to cut down or quit smoking six to eight weeks prior to knee or hip replacement surgery were much less likely to suffer complications.
The Effects of Smoking on Other Disorders Related to Aging
People who smoke also endanger other parts of their bodies as they age. The following are age-related conditions that occur at higher rates in smokers than nonsmokers: