regarding 20 popular recreational drugs. Tobacco was ranked 3rd in dependence, 14th in physical harm and 12th in social harm. Smoking most commonly leads to diseases affecting the heart and
lungs and will commonly affect areas such as hands or feet. First signs of smoking-related health issues often show up as numbness in the extremities, with smoking being a major risk factor for
heart attacks,
chronic obstructive pulmonary disease (COPD),
emphysema, and
cancer, particularly
lung cancer, cancers of the
larynx and
mouth, and
pancreatic cancer. The immune system is also weakened by smoking, which makes the body more susceptible to infections and takes longer to recover from injuries. Overall life expectancy is also reduced in long term smokers, with estimates ranging from 10 to 17.9 years fewer than non-smokers. About one-half of men who smoke long-term will die of illness due to smoking. The association of smoking with lung cancer and COPD is among the strongest, both in the public perception and etiologically. Among male smokers, the lifetime risk of developing lung cancer is 17%; among female smokers, the risk is 12%. This risk is significantly lower in non-smokers: 1.3% in men and 1.4% in women. For COPD, the 25 year
incidence of moderate and severe COPD is at least 21% for continuous smokers and 4% for non-smokers, with no difference being reported between men and women. A person's increased
risk of contracting disease is related to the length of time that a person continues to smoke as well as the amount smoked. However, even smoking one cigarette a day raises the risk of
coronary heart disease by about 50% or more, and for
stroke by about 30%. Smoking 20 cigarettes a day entails a higher risk, but not proportionately. If someone stops smoking, then these chances gradually decrease as the damage to their body is repaired. A year after quitting, the risk of contracting heart disease is half that of a continuing smoker. The health risks of smoking are not uniform across all smokers. Risks vary according to the amount of tobacco smoked, with those who smoke more at greater risk. Smoking so-called "light" cigarettes does not reduce the risk.
Mortality Smoking is the cause of more than 7 million deaths per year. One study found that male and female smokers lose an average of 13 and 15 years of life, respectively. Another measured a loss of life of 7 years. Each cigarette that is smoked is estimated to shorten life by an average of 11 minutes, though this may vary slightly depending on the contents and brand. More recently, it has been reported to be 20 minutes. At least half of all lifelong smokers die early as a result of smoking. In the United States, cigarette smoking and exposure to tobacco smoke account for roughly one in five, or at least 443,000 premature deaths annually. To put this into context, ABC's
Peter Jennings (who would later die at 67 from complications of lung cancer caused by life-long smoking) famously reported that in the US alone, smoking tobacco kills the equivalent of three
jumbo jets full of people crashing every day, with no survivors. On a worldwide basis, this equates to a single jumbo jet every hour. A 2015 study found that about 17% of mortality due to cigarette smoking in the United States is due to diseases outside of those commonly linked with smoking. Official estimates may therefore be significantly underestimating the number of deaths currently being attributed to smoking. It is estimated that there are between 1 and 1.4 deaths per million cigarettes smoked. Cigarette factories are the most deadly factories in the history of the world. See the below chart detailing the highest-producing cigarette factories, and their estimated deaths caused annually due to the health detriments of cigarettes. File:Death-rate-smoking.png|The number of deaths worldwide attributed to smoking per 100,000 people in 2017
Cancer The primary risks of tobacco usage include many forms of cancer, particularly
lung cancer,
kidney cancer,
cancer of the larynx and
head and neck,
bladder cancer,
esophageal cancer,
pancreatic cancer,
stomach cancer, and
penile cancer. Tobacco smoke can increase the risk of
cervical cancer in women. There may be a small increased risk of
myeloid leukemia,
squamous cell sinonasal cancer,
liver cancer,
colorectal cancer, cancers of
the gallbladder,
the adrenal gland,
the small intestine, and various childhood cancers.
Mouth Perhaps the most serious oral condition caused by smoking (including
pipe smoking) is
oral cancer. However, smoking also increases the risk for various other oral diseases, some almost completely exclusive to tobacco users. Roughly half of
periodontitis or inflammation around the teeth cases are attributed to current or former smoking. Smokeless tobacco causes
gingival recession and white mucosal
lesions. Up to 90% of periodontitis patients who are not helped by common modes of treatment are smokers. Smokers have significantly greater loss of bone height than non-smokers, and the trend can be extended to pipe smokers to have more bone loss than non-smokers. Smoking traditional cigarettes, e-cigarettes, and heat-not-burn products also affects the salivary cytokine levels needed in immune responses. Traditional cigarettes slightly intensify the immune response in long-term smokers compared to non-smokers, with long-term smokers showing higher levels of IFN-γ than non-smokers. E-cigarettes and heat-not-burn products, while marketed as a healthier alternative, have been shown to inhibit immune response function. Users of these products show lower levels of salivary cytokines, chemokines, and growth factors that function to keep the immune response strong and active in the mouth. Smoking has been proven to be an important factor in teeth staining.
Halitosis or bad breath is common among tobacco smokers. Tooth loss is 2 to 3 times higher in smokers than in non-smokers. In addition, complications may further include
leukoplakia, the adherent white plaques or patches on the mucous membranes of the oral cavity, including the tongue.
Head and neck cancer Tobacco smoking is one of the main risk factors for
head and neck cancer. Cigarette smokers have a lifetime increased risk for head and neck cancer that is 5 to 25 times higher than the general population. The person who used to smoke's risk of developing head and neck cancer begins to approach the risk in the general population 15 years after
smoking cessation. In addition, people who smoke have a worse prognosis than those who have never smoked. Furthermore, people who continue to smoke after a diagnosis of head and neck cancer have the highest probability of dying compared to those who have never smoked. This effect is seen in patients with HPV-positive head and neck cancer as well.
Passive smoking, both at work and at home, also increases the risk of head and neck cancer. Using tobacco together with alcohol is an especially strong risk factor for head and neck cancer, causing 72% of all cases. This rises to 89% when looking specifically at
laryngeal cancer.
Smokeless tobacco (including products where tobacco is
chewed) is also a cause of oral cancer.
Cigar and
pipe smoking are also important risk factors for oral cancer. They have a dose-dependent relationship with more consumption leading to higher chances of developing cancer. The use of
electronic cigarettes may also lead to the development of head and neck cancers due to the substances like
propylene glycol,
glycerol,
nitrosamines, and metals contained therein, which can cause damage to the airways. The risk of lung cancer is highly influenced by smoking, with up to 90% of diagnoses being attributed to tobacco smoking. The risk of developing lung cancer increases with the number of years smoked and the number of cigarettes smoked per day. Smoking can be linked to all subtypes of lung cancer.
Small-cell carcinoma (SCLC) is the most closely associated with almost 100% of cases occurring in smokers. This form of cancer has been identified with autocrine growth loops,
proto-oncogene activation and inhibition of
tumor suppressor genes. SCLC may originate from neuroendocrine cells located in the bronchus called Feyrter cells. The risk of dying from lung cancer before age 85 is 22% for a male smoker and 12% for a female smoker, in the absence of competing causes of death. The corresponding estimates for lifelong non-smokers are a 1.1% probability of dying from lung cancer before age 85 for a man of European descent and a 0.8% probability for a woman.
Pulmonary effects In smoking, long-term exposure to compounds found in the smoke (e.g.,
carbon monoxide and
cyanide) are believed to be responsible for pulmonary damage and for loss of elasticity in the
alveoli, leading to emphysema and
chronic obstructive pulmonary disease (COPD). COPD caused by smoking is a permanent, incurable (often terminal) reduction of pulmonary capacity characterized by shortness of breath, wheezing, persistent cough with
sputum, and damage to the lungs, including
emphysema and
chronic bronchitis. The carcinogen acrolein and its derivatives also contribute to the chronic inflammation present in COPD.
Cardiovascular disease , leading to
coronary artery disease and
peripheral arterial disease. Inhalation of tobacco smoke causes several immediate responses within the heart and blood vessels. Within one minute, the heart rate begins to rise, increasing by as much as 30 percent during the first 10 minutes of smoking. Carbon monoxide in tobacco smoke exerts
negative effects by reducing the blood's oxygen-carrying ability. Smoking also increases the chance of
heart disease,
stroke,
atherosclerosis, and
peripheral artery disease. Several ingredients of tobacco lead to the narrowing of blood vessels, increasing the likelihood of a blockage, and thus a
heart attack or stroke. According to a study by an international team of researchers, people under 40 are five times more likely to have a heart attack if they are smokers. Exposure to tobacco smoke is known to increase
oxidative stress in the body by various mechanisms, including depletion of plasma antioxidants such as
vitamin C. Research by American biologists has shown that cigarette smoke also influences the process of cell division in the cardiac muscle and changes the heart's shape. Smoking tobacco has also been linked to
Buerger's disease (
thromboangiitis obliterans), the acute inflammation and thrombosis (clotting) of arteries and veins of the hands and feet. Although cigarette smoking causes a greater increase in the risk of cancer than cigar smoking, people who smoke cigars still have an increased risk for many health problems, including cancer, when compared to people who do not smoke. As for second-hand smoke, the NIH study points to the large amount of smoke generated by one cigar, saying "cigars can contribute substantial amounts of tobacco smoke to the indoor environment; and, when large numbers of cigar smokers congregate in a cigar smoking event, the amount of ETS (i.e. second-hand smoke) produced is sufficient to be a health concern for those regularly required to work in those environments." Smoking also tends to
increase blood cholesterol levels. Furthermore, the ratio of
high-density lipoprotein (HDL, commonly referred to as "good" cholesterol) to
low-density lipoprotein (LDL, commonly referred to as "bad" cholesterol) tends to be lower in smokers compared to non-smokers. Smoking also raises the levels of
fibrinogen and increases
platelet production (both involved in blood clotting), which makes the blood thicker and more likely to clot. Carbon monoxide binds to
hemoglobin (the oxygen-carrying component in red blood cells), resulting in a much more stable complex than hemoglobin bound with oxygen or carbon dioxide—the result is permanent loss of blood cell functionality. Blood cells are naturally recycled after a certain period, allowing for the creation of new, functional red blood cells. However, if carbon monoxide exposure reaches a certain point before it can be recycled, hypoxia (and later death) occurs. All these factors make smokers more at risk of developing various forms of
arteriosclerosis (hardening of the arteries). As the arteriosclerosis progresses, blood flows less easily through rigid and narrowed blood vessels, making the blood more likely to form a thrombosis (clot). Sudden blockage of a blood vessel may lead to an infarction (stroke or heart attack). However, the effects of smoking on the heart may be more subtle. These conditions may develop gradually, given the smoking-healing cycle (the human body heals itself between periods of smoking). Therefore, a person who smokes may develop less significant disorders, such as worsening or maintenance of unpleasant dermatological conditions, e.g., eczema, due to reduced blood supply. Smoking also increases
blood pressure and weakens blood vessels. A history of smoking encourages the progression of
diabetic nephropathy.
Infections Smoking is also linked to susceptibility to infectious diseases, particularly in the lungs (
pneumonia). Smoking more than 20
cigarettes a day increases the risk of
tuberculosis by two to four times, and being a current smoker has been linked to a fourfold increase in the risk of invasive disease caused by the pathogenic bacteria
Streptococcus pneumoniae. It is believed that smoking increases the risk of these and other pulmonary and respiratory tract infections both through structural damage and through effects on the immune system. The effects on the immune system include an increase in CD4+ cell production attributable to nicotine, which has tentatively been linked to increased HIV susceptibility. Smoking increases the risk of
Kaposi's sarcoma in people without
HIV infection. One study found this only with the male population and could not draw any conclusions for the female participants in the study.
Influenza A study of an outbreak of an (
H1N1) influenza in an Israeli military unit of 336 healthy young men to determine the relation of cigarette smoking to the incidence of clinically apparent influenza, revealed that, of 168 smokers, 69% had influenza, as compared with 47% of non-smokers. Influenza was also more severe in the smokers; 51% of them lost work days or required bed rest, or both, as compared with 30% of the non-smokers. According to a study of 1,900 male cadets after the 1968 Hong Kong A2 influenza epidemic at a South Carolina military academy, compared with people who did not smoke, people who smoked heavily (more than 20 cigarettes per day) had 21% more illnesses and 20% more bed rest, people who smoked lightly (20 cigarettes or fewer per day) had 10% more illnesses and 7% more bed rest. The effect of cigarette smoking on epidemic influenza was studied prospectively among 1,811 male college students. Clinical influenza incidence among those who smoked 21 or more cigarettes daily was 21% higher than that of people who did not smoke. Influenza incidence among people who smoked 1 to 20 cigarettes daily was intermediate between those who did not smoke and people who smoked heavily. Smoking seems to cause a higher relative influenza risk in older populations than in younger populations. In a prospective study of community-dwelling people 60–90 years of age, in 1993, of unimmunized people, 23% of people who smoked had clinical influenza compared with 6% of people who did not smoke. Smoking may substantially contribute to the growth of influenza epidemics affecting the entire population. Smoking is a key cause of erectile dysfunction (ED).
Female infertility corrective statement: "Smoking also causes reduced fertility, low birth weight in newborns, and cancer of the cervix" (United States, 2024). Smoking is harmful to the
ovaries, potentially causing
female infertility, and the degree of damage is dependent upon the amount and length of time a woman smokes. Nicotine and other harmful chemicals in cigarettes interfere with the body's ability to create
estrogen, a
hormone that regulates
folliculogenesis and
ovulation. Also, cigarette smoking interferes with folliculogenesis, embryo transport,
endometrial receptivity, endometrial
angiogenesis, uterine blood flow, and the
uterine myometrium. Some damage is irreversible, but stopping smoking can prevent further damage. Smokers are 60% more likely to be infertile than non-smokers.
Effects on pregnancy A number of studies have shown that tobacco use is a significant factor in
miscarriages among
pregnant smokers, and that it contributes to a number of other threats to the health of the fetus such as
low birth weight and
pre-term birth. It slightly increases the risk of
neural tube defects. Environmental tobacco smoke exposure and maternal smoking during pregnancy have been shown to cause lower infant birth weights.
Multigenerational effects Cigarette smoking has been found to affect global epigenetic regulation of transcription across tissue types. Studies have shown differences in epigenetic markers such as
DNA methylation,
histone modifications and
miRNA expression between smokers and non-smokers. Similar differences exist in children whose mothers smoked during pregnancy. These epigenetic effects are thought to be linked to many of negative health effects associated with smoking. Studies have shown an association between prenatal exposure to environmental tobacco smoke and conduct disorder in children. As well, postnatal tobacco smoke exposure may cause similar behavioral problems in children.
Psychological American Psychologist stated, "Smokers often report that cigarettes help relieve feelings of stress. However, the stress levels of adult smokers are slightly higher than those of nonsmokers, adolescent smokers report increasing levels of stress as they develop regular patterns of smoking, and smoking cessation leads to reduced stress. Far from acting as an aid for mood control, nicotine dependency seems to exacerbate stress. This is confirmed in the daily mood patterns described by smokers, with normal moods during smoking and worsening moods between cigarettes. Thus, the apparent relaxant effect of smoking only reflects the reversal of the tension and irritability that develop during
nicotine depletion. Dependent smokers need nicotine to remain feeling normal."
Immediate effects Users report feelings of
relaxation, sharpness,
calmness, and
alertness. Those new to smoking may experience
nausea,
dizziness,
coughing and a bad taste in the mouth, Generally, the unpleasant symptoms will eventually vanish over time, with repeated use, as the body builds a
tolerance to the chemicals in the cigarettes, such as
nicotine. The structural cardiovascular damage is not fully reversible, while the functional changes are mostly reversible after quitting. The onset of these symptoms is very fast, nicotine's half-life being only two hours. The
psychological dependence may linger for months or even many years. Nicotine withdrawal has been shown to cause clinically significant distress. Medical researchers have found that smoking is a predictor of divorce. Smokers have a 53% greater chance of divorce than non-smokers.
Cognitive function In many respects,
nicotine acts on the nervous system in a similar way to
caffeine. Some writings have stated that smoking can also increase
mental concentration; one study documents a significantly better performance on the normed
Advanced Raven Progressive Matrices test after smoking. However, the long term usage of tobacco can create cognitive dysfunction. There seems to be an increased risk of
Alzheimer's disease (AD), although "case–control and cohort studies produce conflicting results as to the direction of the association between smoking and AD". Smoking has been found to contribute to dementia and cognitive decline, reduced memory and cognitive abilities in adolescents, and brain shrinkage (cerebral atrophy).
Alzheimer's disease Some studies have found that patients with Alzheimer's disease are more likely not to have smoked than the general population, which has been interpreted to suggest that smoking offers some protection against Alzheimer's. However, the research in this area is limited and the results are conflicting; some studies show that smoking increases the risk of Alzheimer's disease. A recent review of the available scientific literature concluded that the apparent decrease in Alzheimer's risk may be simply because smokers tend to die before reaching the age at which Alzheimer's normally occurs. "Differential mortality is always likely to be a problem where there is a need to investigate the effects of smoking in a disorder with very low incidence rates before age 75 years, which is the case of Alzheimer's disease," it stated, noting that smokers are only half as likely as non-smokers to survive to the age of 80. More recent analysis has found that most of the studies which showed a preventing effect were closely affiliated with the tobacco industry. Researchers without tobacco lobby influence have concluded the complete opposite: Smokers are almost twice as likely as non-smokers to develop Alzheimer's disease.
Parkinson's disease In the case of Parkinson's disease, a series of observational studies that consistently suggest a possibly substantial reduction in risk among smokers (and other consumers of
tobacco products) has led to longstanding interest among epidemiologists. Non-biological factors that may contribute to such observations include reverse
causality (whereby
prodromal symptoms of Parkinson's disease may lead some smokers to quit before diagnosis), and personality considerations (people predisposed to Parkinson's disease tend to be relatively
risk-averse, and may be less likely to have a history of smoking). A data-driven hypothesis that long-term administration of very low doses of nicotine (for example, in an ordinary diet) might provide a degree of
neurological protection against Parkinson's disease remains open as a potential
preventive strategy.
Mental health The high rate of smoking tobacco by people with mental health problems is a major factor in their decreased life expectancy, which is about 25 years shorter than that of the general population.
Stress Smokers report higher levels of everyday stress. Several studies have monitored feelings of stress over time and found reduced stress after quitting. The deleterious mood effects of everyday between-cigarette nicotine withdrawal symptoms explain why people who smoke experience more daily stress than non-smokers, and become less stressed when they quit smoking. Deprivation reversal also explains much of the arousal data, with deprived smokers being less vigilant and less alert than non-deprived smokers or non-smokers.
Schizophrenia A very large percentage of
schizophrenics smoke tobacco as a form of self-medication. Some studies suggest that a link exists between smoking and mental illness, citing the high incidence of smoking amongst those with
schizophrenia and smoking lowering age of the onset of psychosis. In 2015, a meta-analysis found that smokers were at greater risk of developing psychotic illness. However, following the observation that smoking improves the condition of people with schizophrenia, in particular their working memory deficit,
nicotine patches had been proposed as a way to treat schizophrenia.
Anxiety disorders Recent studies have linked smoking to anxiety disorders, suggesting the correlation (and possibly mechanism) may be related to the broad class of anxiety disorders, and not limited to just depression. Current and ongoing research attempts to explore the addiction-anxiety relationship. Data from multiple studies suggest that anxiety disorders and depression play a role in cigarette smoking. A history of regular smoking was observed more frequently among individuals who had experienced a
major depressive disorder at some time in their lives than among individuals who had never experienced major depression or among individuals with no psychiatric diagnosis. People with major depression are also much less likely to
quit due to the increased risk of experiencing mild to severe states of depression, including a major depressive episode. Depressed smokers appear to experience more withdrawal symptoms on quitting, are less likely to be successful at quitting, and are more likely to relapse.
Drug interactions Smoking is known to increase levels of liver enzymes that break down drugs and toxins. That means that drugs cleared by these enzymes are cleared more quickly in smokers, which may result in the drugs not working. Specifically, levels of CYP1A2 and CYP2A6 are induced: substrates for 1A2 include
caffeine and tricyclic antidepressants such as
amitriptyline; substrates for 2A6 include the anticonvulsant
valproic acid.
Other harm Studies suggest that smoking decreases appetite, but did not conclude that overweight people should smoke or that their health would improve by smoking, because this habit is a cause of heart disease. Smoking also decreases weight by overexpressing the gene
AZGP1, which stimulates
lipolysis. Smoking causes about 10% of the global burden of fire deaths, and smokers are placed at an increased risk of injury-related deaths in general, partly due to also experiencing an increased risk of dying in a motor vehicle crash. Smoking increases the risk of symptoms associated with
Crohn's disease (a dose-dependent effect with use of greater than 15 cigarettes per day). There is some evidence for decreased rates of
endometriosis in infertile smoking women, although other studies have found that smoking increases the risk in infertile women. There is little or no evidence of a protective effect in fertile women. Some preliminary data from 1996 suggested a reduced incidence of
uterine fibroids, but overall the evidence is unconvincing. Current research shows that tobacco smokers who are exposed to residential radon are twice as likely to develop lung cancer as non-smokers. As well, the risk of developing lung cancer from asbestos exposure is twice as likely for smokers than for non-smokers. New research has found that women who smoke are at significantly increased risk of developing an
abdominal aortic aneurysm, a condition in which a weak area of the
abdominal aorta expands or bulges, and is the most common form of
aortic aneurysm. Smoking leads to an increased risk of
bone fractures, especially
hip fractures. It also leads to slower
wound healing after surgery, and an increased rate of postoperative healing complication. Tobacco smokers are 30-40% more likely to develop
type 2 diabetes than non-smokers, and the risk increases with the number of cigarettes smoked. Furthermore, diabetic smokers have worse outcomes than diabetic non-smokers.
Claimed benefits History of claimed benefits In 1888, an article appeared in
Scientific American discussing potential
germicidal activity of tobacco smoke providing immunity against
yellow fever epidemic of Florida inspiring research in the lab of
Vincenzo Tassinari at the Hygienic Institute of the
University of Pisa, who explored the antimicrobial activity against pathogens including
Bacillus anthracis,
Mycobacterium tuberculosis,
Bacillus prodigiosus,
Staphylococcus aureus, and others.
Carbon monoxide is a bioactive component of tobacco smoke that has been explored for its antimicrobial properties against many of these pathogens. On epidemiological grounds, unexpected correlations between smoking and favorable outcomes initially emerged in the context of cardiovascular disease, where they were described as a '''smoker's paradox
(or smoking paradox'
). The term smoker's paradox'' was coined in 1995 in relation to reports that smokers appeared to have unexpectedly good short-term outcomes following
acute coronary syndrome or stroke. In the same year, a
case–control study first suggested a possible protective role in Parkinson's disease. Historical claims of possible benefits
in schizophrenia, whereby smoking was thought to ameliorate
cognitive symptoms, are not supported by current evidence.
Mechanism Against the background of the overwhelmingly negative effects of smoking on health, some
observational studies have suggested that smoking might have specific beneficial effects, including in the field of
cardiovascular disease.
melanoma,
pemphigus,
celiac disease, and
ulcerative colitis, among others. Tobacco smoke has many bioactive substances, including
nicotine, that are capable of exerting a variety of
systemic effects. ==Mechanisms of negative health effects==