Health Effects of Tobacco

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Health effects of tobaccoFrom Wikipedia, the free encyclopediaJump to: navigation, search The health effects of tobacco are the circumstances, mechanisms, and factors of tobacco consumption onhuman health. Epidemiological research has been focused primarily on cigarette tobacco smoking,[1] whichhas been studied more extensively than any other form of consumption.[2]

Tobacco is the single greatest cause of preventable death globally.[3] Tobacco use leads most commonly todiseases affecting the heart and lungs, with smoking being a major risk factor for heart attacks, strokes,chronic obstructive pulmonary disease (COPD) (including emphysema and chronic bronchitis), and cancer (particularly lung cancer , cancers of the larynx and mouth, and pancreatic cancer ). It also causes peripheralvascular disease and hypertension. The effects depend on the number of years that a person smokes and onhow much the person smokes. Starting smoking earlier in life and smoking cigarettes higher in tar increasesthe risk of these diseases. Cigarettes sold in underdeveloped countries tend to have higher tar content, and areless likely to be filtered, potentially increasing vulnerability to tobacco-related disease in these regions.[4] The World Health Organization (WHO) estimates that tobacco caused 5.4 million deaths in 2004[5] and 100million deaths over the course of the 20th century.[6] Similarly, the United States Centers for Disease Controland Prevention describes tobacco use as "the single most important preventable risk to human health in

developed countries and an important cause of premature death worldwide."[7]

Smoke contains several carcinogenic pyrolytic products that bind to DNA and cause many genetic mutations.There are over 19 known chemical carcinogens in cigarette smoke[citation needed ]. Tobacco also contains nicotine,which is a highly addictive psychoactive chemical. When tobacco is smoked, nicotine causes physical and psychological dependency. Tobacco use is a significant factor in miscarriages among pregnant smokers, itcontributes to a number of other threats to the health of the fetus such as premature births and low birthweight and increases by 1.4 to 3 times the chance for Sudden Infant Death Syndrome (SIDS).[8] The result of scientific studies done in neonatal rats seems to indicate that exposure to cigarette smoke in the womb mayreduce the fetal brain's ability to recognize hypoxic conditions, thus increasing the chance of accidentalasphyxiation.[9] Incidence of impotence is approximately 85 percent higher in male smokers compared to non-smokers,[10] and is a key factor causing erectile dysfunction (ED).

[10][11][12]

Prevalence

Percentage of females smoking any tobacco product

Percentage of males smoking any tobacco product. Note that there is a difference between the scales used for

females and the scales used for males.[13]

Tobacco may be consumed by either smoking or other smokeless methods such as chewing, the World HealthOrganization (WHO) only collect data on smoked tobacco.[1] Smoking has therefore been studied moreextensively than any other form of consumption.[2]



In 2000, smoking was practiced by 1.22 billion people, predicted to rise to 1.45 billion people in 2010 and 1.5to 1.9 billion by 2025. If prevalence had decreased by 2% a year since 2000 this figure would have been 1.3 billion in 2010 and 2025.[14] Despite dropping by 0.4 percent from 2009 to 2010, the United States still reportsan average of 17.9 percent usage.[15] Smoking is generally five times more prevalent among males than females,[14] however the gender gapdeclines with younger age.[16][17] In developed countries smoking rates for men have peaked and have begunto decline, however for women they continue to climb.[18]

As of 2002, about twenty percent of young teens (13±15) smoke worldwide, with 80,000 to 100,000 childrentaking up the addiction every day²roughly half of whom live in Asia. Half of those who begin smoking inadolescent years are projected to go on to smoke for 15 to 20 years.[19] The WHO states that "Much of the disease burden and premature mortality attributable to tobacco usedisproportionately affect the poor". Of the 1.22 billion smokers, 1 billion of them live in developing or transitional nations. Rates of smoking have leveled off or declined in the developed world.[20] In thedeveloping world, however, tobacco consumption is rising by 3.4% per year as of 2002.[19] The WHO in 2004 projected 58.8 million deaths to occur globally,[21] from which 5.4 million are tobacco-attributed,[22] and 4.9 million as of 2007.[23] As of 2002, 70% of the deaths are in developing countries.[23] The shift in prevalence of tobacco smoking to a younger demographic, mainly in the developing world, can beattributed to several factors. The tobacco industry spends up to $12.5 billion annually on advertising, which is

increasingly geared towards adolescents in the developing world because they are a very vulnerable audiencefor the marketing campaigns. Adolescents have more difficulty understanding the long term health risks thatare associated with smoking and are also more easily influenced by ³images of romance, success,sophistication, popularity, and adventure which advertising suggests they could achieve through theconsumption of cigarettes´. This shift in marketing towards adolescents and even children in the tobaccoindustry is debilitating to organizations¶ and countries¶ efforts to improve child health and mortality in thedeveloping world. It reverses or halts the effects of the work that has been done to improve health care inthese countries, and although smoking is deemed as a ³voluntary´ health risk, the marketing of tobaccotowards very impressionable adolescents in the developing world makes it less of a voluntary action and moreof an inevitable shift.[24] Studies

In the 1930s German scientists showed that cigarette smoking caused lung cancer.[25]

In 1938 a study by aJohns Hopkins University scientist suggested a strongly negative correlation between smoking and lifespan.In 1950 five studies were published in which "smoking was powerfully implicated in the causation of lungcancer".[26] These included the now classic paper "Smoking and Carcinoma of the Lung" which appeared inthe Br itish Medical Jour nal . This paper reported that "heavy smokers were fifty times as likely as non-smokers to contract lung cancer".

[26][27]

In 1953 scientists at the Sloan-Kettering Institute in New York City demonstrated that cigarette tar painted onthe skin of mice caused fatal cancers.[28] This work attracted much media attention; the New York Times and Life both covered the issue. The Reader' s Digest published an article entitled "Cancer by the Carton".

[28]

A team of British scientists headed by Richard Doll carried out a longitudinal study of 34,439 medicalspecialists from 1951 to 2001, generally called the "British Doctors Study."[29] The study demonstrated that

about half of the persistent cigarette smokers born in 1900±1909 were eventually killed by their addiction(calculated from the logarithms of the probabilities of surviving from 35±70, 70±80, and 80±90) and abouttwo thirds of the persistent cigarette smokers born in the 1920s would eventually be killed by their addiction.After a ban on smoking in all enclosed public places was introduced in Scotland in March 2006, there was a17 percent reduction in hospital admissions for acute coronary syndrome. 67% of the decrease occurred innon-smokers.[30] The health effects of tobacco have been significant for the development of the science of epidemiology. Asthe mechanism of carcinogenicity is radiomimetic or radiological, the effects are stochastic. Definite



statements can be made only on the relative increased or decreased probabilities of contracting a givendisease; Philosophically and theoretically speaking, it is impossible to definitively prove a direct causativelink between exposure to a radiomimetic poison such as tobacco smoke and the cancer that follows. Tobaccocompanies have capitalized on this philosophical objection and exploited the doubts of clinicians, whoconsider only individual cases, on the causal link in the stochastic expression of the toxicity as actualdisease.[31] There have been multiple court cases on the issue that tobacco companies have researched the health effects

of tobacco, but suppressed the findings or formatted them to imply lessened or no hazard.[31] A study published in the journal P ediat r ics

[32]refers to the danger posed by what the authors call "third-hand

smoke" ² toxic substances that remain in areas where smoking has recently occurred. The study wasreviewed in an story broadcast by the Voice of America.

Occasional SmokingThe term "smoker" is used to mean a person who habitually smokes tobacco on a daily basis. This categoryhas been the focus of the vast majority of tobacco studies. However, the health effects of less-than-dailysmoking are far less well understood. Studies have often taken the data of "occasional smokers" (those whohave never smoked daily) and grouped them with those who have never smoked.[33] A recent European study on occasional smoking published findings that the risk of the major smoking-relatedcancers for occasional smokers was 1.24 times that of those who have never smoked at all but the result was

not statistically significant. (For a confidence interval of 95%, this data showed an incidence rate ratio of 0.80to 1.94.)[33] This compares to studies showing that habitual heavy smokers have greater than 50 times theincidence of smoking-related cancers.

Mechanism See also: List of additives in cigarettes

Chemical carcinogens

Benzopyrene diol epoxide, an extremely carcinogenic (cancer-causing) metabolite of benzopyrene, a polynuclear

aromatic hydrocarbon produced by burning tobacco.

Benzopyrene, a major mutagen in tobacco smoke, in an adduct to DNA.[34]

Smoke, or any partially burnt organic matter, contains carcinogens (cancer-causing agents). The potentialeffects of smoking, such as lung cancer, can take up to 20 years to manifest themselves. Historically, women began smoking en masse later than men, so an increased death rate caused by smoking amongst women didnot appear until later. The male lung cancer death rate decreased in 1975 ² roughly 20 years after the initial



decline in cigarette consumption in men. A fall in consumption in women also began in 1975 but by 1991 hadnot manifested in a decrease in lung cancer related mortalities amongst women.

[35]

Smoke contains several carcinogenic pyrolytic products that bind to DNA and cause genetic mutations.Particularly potent carcinogens are polynuclear aromatic hydrocarbons (PAH), which are toxicated tomutagenic epoxides. The first PAH to be identified as a carcinogen in tobacco smoke was benzopyrene, whichhas been shown to toxicate into an epoxide that irreversibly attaches to a cell's nuclear DNA, which mayeither kill the cell or cause a genetic mutation. If the mutation inhibits programmed cell death, the cell can

survive to become a cancer cell. Similarly, acrolein, which is abundant in tobacco smoke, also irreversibly binds to DNA, causes mutations and thus also cancer. However, it needs no activation to becomecarcinogenic.[36] There are over 19 known carcinogens in cigarette smoke.[37] The following are some of the most potentcarcinogens:

y Polynuclear aromatic hydrocarbons are tar components produced by pyrolysis in smoldering organic matter

and emitted into smoke. Many of them are highly carcinogenic and mutagenic, because they are toxicated to

mutagenic epoxides, which are electrophilic alkylating agents. The first PAH to be identified as a carcinogen in

tobacco smoke was benzopyrene, which been shown to toxicate into a diol epoxide and then permanently

attach to nuclear DNA, which may either kill the cell or cause a genetic mutation. The DNA contains the

information on how the cell function; in practice, it contains the recipes for protein synthesis. If the mutation

inhibits programmed cell death, the cell can survive to become a cancer cell, a cell that does not function like anormal cell. The carcinogenity is radiomimetic, i.e. similar to that produced by ionizing nuclear radiation.

Tobacco manufacturers have experimented with combustionless vaporizer technology to allow cigarettes to

be consumed without the formation of carcinogenic benzopyrenes.[38]

However, such products have become

increasingly popular, with world wide markets claiming a safer smoke. No conclusive evidence has shown to

prove or disprove health claims.[citation needed ]

y Acrolein is a pyrolysis product that is abundant in cigarette smoke. It gives smoke an acrid smell and an

irritating, lachromatory effect and is a major contributor to its carcinogenity. Like PAH metabolites, acrolein is

also an electrophilic alkylating agent and permanently binds to the DNA base guanine, by a conjugate addition

followed by cyclization into a hemiaminal. The acrolein-guanine adduct induces mutations during DNA copying

and thus causes cancers in a manner similar to PAHs. However, acrolein is 1000 times more abundant than

PAHs in cigarette smoke, and is able to react as is, without metabolic activation. Acrolein has been shown to

be a mutagen and carcinogen in human cells. The carcinogenity of acrolein has been difficult to study by

animal experimentation, because it has such a toxicity that it tends to kill the animals before they develop

cancer.[36]

Generally, compounds able to react by conjugate addition as electrophiles (so-calledMichael

acceptors after Michael reaction) are toxic and carcinogenic, because they can permanently alkylate DNA,

similarly to mustard gas or aflatoxin. Acrolein is only one of them present in cigarette smoke; for example,

crotonaldehyde has been found in cigarette smoke.[39]

Michael acceptors also contribute to the chronic

inflammation present in tobacco disease.[40]

y Nitrosamines are a group of carcinogenic compounds found in cigarette smoke but not in uncured tobacco

leaves. Nitrosamines form on flue-cured tobacco leaves during the curing process through a chemical reaction

between nicotine and other compounds contained in the uncured leaf and various oxides of nitrogen found in

all combustion gases. Switching to Indirect fire curing has been shown to reduce nitrosamine levels to less

than 0.1 parts per million.[41][42]

Radioactive carcinogens

In addition to chemical, nonradioactive carcinogens, tobacco and tobacco smoke contain small amounts of lead-210 (210Pb) and polonium-210 (210Po) both of which are radioactive carcinogens. The presence of polonium-210 in mainstream cigarette smoke has been experimentally measured at levels of 0.0263±0.036 pCi (0.97±1.33 mBq),

[citation needed ][43]which is equivalent to about 0.1 pCi per milligram of smoke (4

mBq/mg); or about 0.81 pCi of lead 210 per gram of dry condensed smoke (30 Bq/kg).



Research by NCAR radiochemist Ed Martell determined that radioactive compounds in cigarette smoke aredeposited in "hot spots" where bronchial tubes branch. Since tar from cigarette smoke is resistant to dissolvingin lung fluid, the radioactive compounds have a great deal of time to undergo radioactive decay before beingcleared by natural processes. Indoors, these radioactive compounds linger in secondhand smoke, and thereforegreater exposure occurs when these radioactive compounds are inhaled during normal breathing, which isdeeper and longer than when inhaling cigarettes. Damage to the protective epithelial tissue from smoking onlyincreases the prolonged retention of insoluble polonium 210 compounds produced from burning tobacco.

Martell estimated that a carcinogenic radiation dose of 80±100 rads is delivered to the lung tissue of mostsmokers who die of lung cancer.

[44]

Smoking an average of 1.5 packs per day gives a radiation dose of 60-160 mSv/year,[45][46][47] compared withliving near a nuclear power station (0.0001 mSv/year)[48][49] or the 3.0 mSv/year average dose for Americans.[49][50] Some of the mineral apatite in Florida used to produce phosphate for U.S.A. tobacco cropscontains uranium, radium, lead 210 and polonium 210 and radon.[51] [52] The radioactive smoke from tobaccofertilized this way is deposited in lungs and releases radiation even if a smoker quits the habit. Thecombination of carcinogenic tar and radiation in a sensitive organ such as lungs increases the risk of cancer. Ifthe smoker also breathes in the asbestos fibers which commonly occur in urban and industrial environments,the risk of cancer is greatly increased.Nicotine

Nicotine molecule Nicotine that is contained in cigarettes and other smoked tobacco products is a stimulant and is one of themain factors leading to continued tobacco smoking. Although the amount of nicotine inhaled with tobaccosmoke is quite small (most of the substance is destroyed by the heat) it is still sufficient to cause physicaland/or psychological dependence. The amount of nicotine absorbed by the body from smoking depends onmany factors, including the type of tobacco, whether the smoke is inhaled, and whether a filter is used.Despite the design of various cigarettes advertised and even tested on machines to deliver less of the toxic tar,studies show that when smoked by humans instead of machines, they deliver the same net amount of smoke.Ingesting a compound by smoking is one of the most rapid and efficient methods of introducing it into the bloodstream, second only to injection, which allows for the rapid feedback which supports the smokers'ability to titrate their dosage. On average it takes about ten seconds for the substance to reach the brain. As a

result of the efficiency of this delivery system, many smokers feel as though they are unable to cease. Of thosewho attempt cessation and last three months without succumbing to nicotine, most are able to remain smokefree for the rest of their lives.[53] There exists a possibility of depression in some who attempt cessation, aswith other psychoactive substances. Depression is also common in teenage smokers; teens who smoke arefour times as likely to develop depressive symptoms as their nonsmoking peers.[54] Although nicotine does play a role in acute episodes of some diseases (including stroke, impotence, and heartdisease) by its stimulation of adrenaline release, which raises blood pressure,[55] heart rate, and free fattyacids, the most serious longer term effects are more the result of the products of the smouldering combustion





Healt h effect s

Nicotine stains on primarily the 2nd and 3rd fingers in a heavy smoker.

A person's increased risk of contracting disease is directly proportional to the length of time that a personcontinues to smoke as well as the amount smoked. However, if someone stops smoking, then these chancesgradually decrease as the damage to their body is repaired. A year after quitting, the risk of contracting heartdisease is half that of a continuing smoker.[68] The health risks of smoking are not uniform across all smokers.Risks vary according to amount of tobacco smoked, with those who smoke more at greater risk. Lightsmoking is still a health risk. Likewise, smoking "light" cigarettes does not reduce the risks.Tobacco use most commonly leads to diseases affecting the heart and lungs, 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 . Overall life expectancy isalso reduced in regular smokers, with estimates ranging from 10[29] to 17.9 [69] years fewer thannonsmokers.[70] About two thirds of male smokers will die of illness due to smoking.[71] The association of smoking with lung cancer is strongest, both in the public perception and etiologically. People who havesmoked tobacco at some point have about a one in ten chance of developing lung cancer during their lifetime.[72] If one looks at men who continue to smoke tobacco, the risk increases to one in six.[73] Historically, lung cancer was considered to be a rare disease prior to World War I and was perceived assomething most physicians would never see during their career. With the postwar rise in popularity of cigarette smoking came a virtual epidemic of lung cancer.[74][75] Mort ality

Male and female smokers lose an average of 13.4 to 14.3 years of life, respectively.[76] According to the results of a 14 year study of 34,486 male British doctors, at least half of all life-long smokersdie earlier as a result of smoking.

[29]

Smokers are three times as likely to die before the age of 60 or 70 as non-smokers.[77][78][79] In the United States alone, cigarette smoking and exposure to tobacco smoke accounts for roughly one infive,

[15]or at at least 443,000 premature deaths annually.

[80]





smoking. Carbon monoxide in tobacco smoke exerts its negative effects by reducing the blood¶s ability tocarry oxygen.

[95]

Smoking also increases the chance of heart disease, stroke, atherosclerosis, and peripheral vascular 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 smoke.[96] Latest research of the American biologists have determined that cigarette smoke also influences the process of

cell division in the cardiac muscle and changes the heart's shape.[97] The usage of tobacco has also been linked to Buerger's disease (thr omboangiitis obliter ans) the acuteinflammation and thrombosis (clotting) of arteries and veins of the hands and feet.[citation needed ] The current Surgeon General¶s Report concluded that there is no risk-free level of exposure to secondhandsmoke. Even short exposures to secondhand smoke can cause blood platelets to become stickier, damage thelining of blood vessels, decrease coronary flow velocity reserves, and reduce heart rate variability, potentiallyincreasing the risk of heart attack . New research indicates that private research conducted by cigarettecompany Philip Morris in the 1980s showed that secondhand smoke was toxic, yet the company suppressedthe finding during the next two decades.[92] Although cigarette smoking causes a greater increase of the risk of cancer than cigar smoking, cigar smokersstill have an increased risk for many health problems, including cancer, when compared to non-smokers.[98][99]

As for Environmental Tobacco Smoke (ETS, or "Second-hand Smoking"), the NIH study points to the largeamount of smoke generated by one cigar, saying "cigars can contribute substantial amounts of tobacco smoketo the indoor environment; and, when large numbers of cigar smokers congregate together in a cigar smokingevent, the amount of ETS produced is sufficient to be a health concern for those regularly required to work inthose environments."[100] Smoking tends to increase blood cholesterol levels. Furthermore, the ratio of high-density lipoprotein (the"good" cholesterol) to low-density lipoprotein (the "bad" cholesterol) tends to be lower in smokers comparedto non-smokers. Smoking also raises the levels of fibrinogen and increases platelet production (both involvedin blood clotting) which makes the blood viscous. Carbon monoxide binds to haemoglobin (the oxygen-carrying component in red blood cells), resulting in a much stabler complex than haemoglobin bound withoxygen or carbon dioxide²the result is permanent loss of blood cell functionality. Blood cells are naturally

recycled after a certain period of time, allowing for the creation of new, functional erythrocytes. However, if carbon monoxide exposure reaches a certain point before they can be recycled, hypoxia (and later death)occurs. All these factors make smokers more at risk of developing various forms of arteriosclerosis. As thearteriosclerosis 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). However, it is also worth noting that the effects of smoking on the heart may be more subtle. Theseconditions may develop gradually given the smoking-healing cycle (the human body heals itself between periods of smoking), and therefore a smoker may develop less significant disorders such as worsening or maintenance of unpleasant dermatological conditions, e.g. eczema, due to reduced blood supply. Smokingalso increases blood pressure and weakens blood vessels.[55] Renal

In addition to increasing the risk of kidney cancer, smoking can also contribute to additional renal damage.Smokers are at a significantly increased risk for chronic kidney disease than non-smokers.[101] A history of smoking encourages the progression of diabetic nephropathy.[102] Influenza

A study of an outbreak of A(H1N1) influenza in an Israeli military unit of 336 healthy young men todetermine the relation of cigarette smoking to the incidence of clinically apparent influenza, revealed that, of 168 smokers, 68.5 percent had influenza, as compared with 47.2 percent of nonsmokers. Influenza was also



more severe in the smokers; 50.6 percent of the smokers lost work days or required bed rest, or both, ascompared with 30.1 percent of the nonsmokers.

[103]

According to a study of 1,900 male cadets after the 1968 Hong Kong A2 influenza epidemic at a SouthCarolina military academy, compared with nonsmokers heavy smokers (more than 20 cigarettes per day), had21% more illnesses and 20% more bed rest, light smokers (less than 20 cigarettes per day) had 10% moreillnesses and 7% more bed rest.[104] The effect of cigarette smoking upon epidemic influenza was studied prospectively among 1,811 male college

students. Clinical influenza incidence among those who daily smoked 21 or more cigarettes was 21% higher than that of non-smokers. Influenza incidence among smokers of 1 to 20 cigarettes daily was intermediate between non-smokers and heavy cigarette smokers.[105] Surveillance of a 1979 influenza out-break at a military base for women in Israel revealed that, Influenzasymptoms developed in 60.0% of the current smokers vs. 41.6% of the nonsmokers.[106] 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, during 1993, of unimmunized people23% of smokers had clinical influenza as compared with 6% of non-smokers.[107] Smoking may substantially contribute to the growth of influenza epidemics affecting the entire population.[103

However the proportion of influenza cases in the general non-smoking population attributable to smokers hasnot yet been calculated.

OralPerhaps the most serious oral condition that can arise is that of oral cancer . However, smoking also increasesthe risk for various other oral diseases, some almost completely exclusive to tobacco users. The NationalInstitutes of Health, through the National Cancer Institute, determined in 1998 that "cigar smoking causes avariety of cancers including cancers of the oral cavity (lip, tongue, mouth, throat), esophagus, larynx, andlung."[100] Pipe smoking involves significant health risks,[108][109] particularly oral cancer.[110][111] Roughly half of periodontitis or inflammation around the teeth cases are attributed to current or former smoking. Smokelesstobacco causes gingival recession and white mucosal lesions. Up to 90% of periodontitis patients who are nothelped by common modes of treatment are smokers. Smokers have significantly greater loss of bone heightthan nonsmokers, and the trend can be extended to pipe smokers to have more bone loss than nonsmokers.

[112]

Smoking has been proven to be an important factor in the staining of teeth.[113][114] Halitosis or bad breath is

common among tobacco smokers.[115]

Tooth loss has been shown to be 2[116]

to 3 times[117]

higher in smokersthan in non-smokers.[118] In addition, complications may further include leukoplakia, the adherent white plaques or patches on the mucous membranes of the oral cavity, including the tongue, and a loss of tastesensation or salivary changes.[citation needed ] Infection

Tobacco is also linked to susceptibility to infectious diseases, particularly in the lungs. Smoking more than 20cigarettes a day increases the risk of tuberculosis by two to four times,[119][120] and being a current smoker has been linked to a fourfold increase in the risk of invasive pneumococcal disease.[121] It is believed that smokingincreases the risk of these and other pulmonary and respiratory tract infections both through structural damageand 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.[122]

The usage of tobacco also increases rates of infection: common cold and bronchitis, chronic obstructive pulmonary disease, emphysema and chronic bronchitis in particular.[citation needed ] Smoking reduces the risk of Kaposi's sarcoma in people without HIV infection.[123] One study found this onlywith the male population and could not draw any conclusions for the female participants in the study.[124] Impot ence

Incidence of impotence is approximately 85 percent higher in male smokers compared to non-smokers,[10] andit is a key cause of erectile dysfunction (ED).

[10][11][12]Smoking causes impotence because it promotes arterial

narrowing.[125]



Female infertility

Smoking is harmful to the ovaries, potentially causing female infertility, and the degree of damage isdependent upon the amount and length of time a woman smokes. Nicotine and other harmful chemicals incigarettes interfere with the body¶s ability to create estrogen, a hormone that regulates folliculogenesis andovulation. Also, cigarette smoking interferes with folliculogenesis, embryo transport, endometrial receptivity,endometrial angiogenesis, uterine blood flow and the uterine myometrium.[126] Some damage is irreversible, but stopping smoking can prevent further damage.[127][128] Smokers are 60% more likely to be infertile than

non-smokers.[129]

Smoking reduces the chances of IVF producing a live birth by 34% and increases the risk ofan IVF pregnancy miscarrying by 30%.[129] Psychological

"Smokers often report that cigarettes help relieve feelings of stress. However, the stress levels of adultsmokers are slightly higher than those of nonsmokers, adolescent smokers report increasing levels of stress asthey develop regular patterns of smoking, and smoking cessation leads to reduced stress. Far from acting as anaid 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 thatdevelop during nicotine depletion. Dependent smokers need nicotine to remain feeling normal." [130] Immediate effects

Users report feelings of relaxation, sharpness, calmness, and alertness.[131]

Those new to smoking mayexperience nausea, dizziness, and rapid heart beat. The unpleasant symptoms will eventually vanish over timewith repeated use, as the body builds a tolerance to the chemicals in the cigarettes, such as nicotine.

Stress

Smokers report higher levels of everyday stress.[132] Several studies have monitored feelings of stress over time and found reduced stress after quitting.[133][134] The deleterious mood effects of abstinence explain why smokers suffer more daily stress than non-smokers,and become less stressed when they quit smoking. Deprivation reversal also explains much of the arousaldata, with deprived smokers being less vigilant and less alert than non-deprived smokers or non-smokers.[132] Social and behavioral

Medical researchers have found that smoking is a predictor of divorce.[135] Smokers have a 53% greater

chance of divorce than nonsmokers.[136]

Cognitive functionThe usage of tobacco can also create cognitive dysfunction. There seems to be in increased risk of Alzheimer's disease, although "case±control and cohort studies produce conflicting results as to the directionof the association between smoking and AD".[137] Smoking has been found to contribute to dementia andcognitive decline,[138] reduced memory and cognitive abilities in adolescents,[139] and brain shrinkage (cerebralatrophy).[140][141] In many respects, nicotine acts on the nervous system in a similar way to caffeine. Some writings have statedthat smoking can also increase mental concentration; one study documents a significantly better performanceon the normed Advanced Raven Progressive Matrices test after smoking.[142] Most smokers, when denied access to nicotine, exhibit symptoms such as irritability, jitteriness, dry mouth,

and rapid heart beat.

[143]

The onset of these symptoms is very fast, nicotine's half-life being only 2 hours.Withdrawal symptoms can appear even if the smoker's consumption is very limited or irregular, appearingafter only 4±5 cigarettes in most adolescents. An ex-smoker's chemical dependence to nicotine will cease afterapproximately ten to twenty days, although the brain's number of nicotine receptors is permanentlyaltered,[144] and the psychological dependence may linger for months or even many years. Unlike somerecreational drugs, nicotine does not measurably alter a smoker's motor skills, judgement, or language abilitieswhile under the influence of the drug. Tobacco withdrawal has been shown to cause clinically significantdistress.[145]



Most notably, some studies have found that patients with Alzheimer's disease are more likely not to havesmoked 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 availablescientific literature concluded that the apparent decrease in Alzheimer risk may be simply because smokerstend to die before reaching the age at which Alzheimer normally occurs. "Differential mortality is alwayslikely 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 smokersare only half as likely as non-smokers to survive to the age of 80.

[137]

Former and current smokers have a lower incidence of Parkinson's disease compared to people who havenever smoked,[146][147] although the authors stated that it was more likely that the movement disorders whichare part of Parkinson's disease prevented people from being able to smoke than that smoking itself was protective. Another study considered a possible role of nicotine in reducing Parkinson's risk: nicotinestimulates the dopaminergic system of the brain, which is damaged in Parkinson's disease, while other compounds in tobacco smoke inhibit MAO-B, an enzyme which produces oxidative radicals by breakingdown dopamine.[148] A very large percentage of schizophrenics smoke tobacco as a form of self medication.[149][150][151][152] Thehigh rate of tobacco use by the mentally ill is a major factor in their decreased life expectancy, which is about

25 years shorter than the general population.[153]

Following the observation that smoking improves conditionof people with schizophrenia, in particular working memory deficit, nicotine patches had been proposed as away to treat schizophrenia.[154] Some studies suggest that a link exists between smoking and mental illness,citing the high incidence of smoking amongst those suffering from schizophrenia[155] and the possibility thatsmoking may alleviate some of the symptoms of mental illness,[156] but these have not been conclusive.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 ongoingresearch attempt to explore the addiction-anxiety relationship.Data from multiple studies suggest that anxiety disorders and depression play a role in cigarette smoking.[157] 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.[158]

People with major depression are alsomuch less likely to quit due to the increased risk of experiencing mild to severe states of depression, includinga major depressive episode.[159] Depressed smokers appear to experience more withdrawal symptoms onquitting, are less likely to be successful at quitting, and are more likely to relapse.[160] Evidence suggests that non-smokers are up to twice as likely as smokers to develop Parkinson's disease or Alzheimer's disease.[161] A plausible explanation for these cases may be the effect of nicotine, a cholinergic stimulant, decreasing the levels of acetylcholine in the smoker's brain; Parkinson's disease occurs when theeffect of dopamine is less than that of acetylcholine. In addition, nicotine stimulates the mesolimbic dopamine pathway (as do other drugs of abuse), causing an effective increase in dopamine levels. Opponents counter bynoting that consumption of pure nicotine may be as beneficial as smoking without the risks associated withsmoking, although this is unlikely due to the importance of the MAO-B inhibitor compounds of tobacco in

preventing neurodegenerative diseases.[citation needed ]

In pregnancy

Main article: Smoking and 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. This can especially be a problem with women who have family history of smoking and live in a smoke filled environment. Womenwho quit smoking and then return to it also develop an increased sensitivity to the effects of smoking on their fetus. Once a woman who was previously a smoker quits and then returns to it while pregnant, the increased



sensitivty to it has a very high chance of suffocating the fetus over a period of days in a slow processeventually causing a misscarriage with a heavy flow to it. Continued smoking after this can cause a woman to become completely infertile altogether preventing them from ever being able to have children by causing permanent damage. Every cigarette smoked after the miscarriage increase the chances of infertility as well as being around second hand smoke. [162][163] Second-hand smoke appears to present an equal danger to the fetus,as one study noted that "heavy pater nal smoking increased the risk of early pregnancy loss."[164] Ot her harm

Studies suggest that smoking decreases appetite, but did not conclude that overweight people should smoke orthat their health would improve by smoking. This is also a cause of heart diseases. However due to some new processes of treating tobacco, especially in the case of cigarette, heavy smokers tend to become overweight asthe processing involves large quantities of starch. This effect is not seen in occasional smokers.[165][166] Smoking also decreases weight by overexpressing the gene AZGP1 which stimulates lipolysis.[167] Smoking causes about 10% of the global burden of fire deaths,[168] and smokers are placed at an increased riskof injury-related deaths in general, partly due to also experiencing an increased risk of dying in a motor vehicle crash.[169] Smoking increases the risk of symptoms associated with Crohn's disease (a dose-dependent effect with use of greater than 15 cigarettes per day).[170][171][172][173] There is some evidence for decreased rates of endometriosisin infertile smoking women,

[174]although other studies have found that smoking increases the risk in infertile

women.[175]

There is little or no evidence of a protective effect in fertile women. Some preliminary data from1996 suggested a reduced incidence of uterine fibroids,[176] but overall the evidence is unconvincing.[177] New research has found that women who smoke are at significantly increased risk of developing anabdominal aortic aneurysm, a condition in which a weak area of the abdominal aorta expands or bulges.[178] Benef it s

Main article: Health benefits of smoking

The risk of symptoms associated with ulcerative colitis has been frequently shown to be reduced by smokerson a dose-dependent basis; the effect is eliminated if the individual stops smoking.[171][172][173][179][180] Preliminary reports suggest that smoking can decrease the incidence of acne prophylactically. This was seen by a decreased percentage ratio of patients needing acne medication versus the percentage of entire populationof smokers. (A smaller percentage of patients who smoked needed medication than found in the population as

a whole).

[181]

Several types of "Smoker¶s Paradoxes",[182] (cases where smoking appears to have specific beneficial effects),have been observed; often the actual mechanism remains undetermined. Nicotine may help enhance memory, at least in adults.[183][184]

Particular f orms of tobacco useChewing tobacco

Chewing tobacco has been known to cause cancer , particularly of the mouth and throat.[185] According to theInternational Agency for Research on Cancer , "Some health scientists have suggested that smokeless tobaccoshould be used in smoking cessation programmes and have made implicit or explicit claims that its use would partly reduce the exposure of smokers to carcinogens and the risk for cancer. These claims, however, are notsupported by the available evidence."[185] Oral and spit tobacco increase the risk for leukoplakia a precursor to

oral cancer .

[186]

Cigars

Like other forms of tobacco use, cigar smoking poses a significant health risk depending on dosage: risks aregreater for those who inhale more when they smoke, smoke more cigars, or smoke them longer.[99] The risk ofdying from any cause is significantly greater for cigar smokers, with the risk particularly higher for smokersless than 65 years old, and with risk for moderate and deep inhalers reaching levels similar to cigarettesmokers.

[187]Little cigars are commonly inhaled and likely pose the same health risks as cigarettes.

[188]The

increased risk for those smoking 1±2 cigars per day is too small to be statistically significant,[187] and the



health risks of the 3/4 of cigar smokers who smoke less than daily are not known[189] and are hard to measure;although it has been claimed that people who smoke few cigars have no increased risk, a more accuratestatement is that their risks are proportionate to their exposure.[190] Health risks are similar to cigarette smoking in nicotine addiction, periodontal health, tooth loss, and many types of cancer, including cancers of the mouth, throat, and esophagus. Cigar smoking also can cause cancers of the lung and larynx, where theincreased risk is less than that of cigarettes. Many of these cancers have extremely low cure rates. Cigar smoking also increases the risk of lung and heart diseases such as chronic obstructive pulmonary disease.[99]

Hook ahsA common belief among users is that the smoke is significantly less dangerous than that from cigarettes.[191] The water moisture induced by the hookah makes the smoke less irritating and may give a false sense of security and reduce concerns about true health effects.[192] Doctors at institutions including the Mayo Clinic have stated that use of hookah can be as detrimental to a person's health as smoking cigarettes,[193][194] and astudy by the World Health Organization also confirmed these findings.[195] Each hookah session typically lasts more than 40 minutes, and consists of 50 to 200 inhalations that eachrange from 0.15 to 0.50 liters of smoke.[196][197] In an hour-long smoking session of hookah, users consumeabout 100 to 200 times the smoke of a single cigarette;[196] in a 45-minute smoking session a typical smoker would inhale 1.7 times the nicotine [198] of a single cigarette. A study in the Jour nal of P er iodontology foundthat water pipe smokers were five times more likely than non-smokers to show signs of gum disease

[citation

needed ]

. People who smoked water pipes had five times the risk of lung cancer of non-smokers.[199]

A study on hookah smoking and cancer in Pakistan was published in 2008. Its objective was "to find serumCEA levels in ever/exclusive hookah smokers, i.e. those who smoked only hookah (no cigarettes, bidis, etc.), prepared between 1 and 4 times a day with a quantity of up to 120 g of a tobacco-molasses mixture each (i.e.the tobacco weight equivalent of up to 60 cigarettes of 1 g each) and consumed in 1 to 8 sessions".Carcinoembryonic antigen (CEA) is a marker found in several forms of cancer. Levels in exclusive hookahsmokers were lower compared to cigarette smokers although the difference was not statistically significant between a hookah smoker and a non-smoker. Also the study concluded that heavy hookah smoking (2±4 daily preparations; 3±8 sessions a day ; >2 hrs to � 6 hours) substantially raises CEA levels.[200] A recent study published in the Asia Pacific Journal of Cancer Prevention (Koul PA et al. Hookah Smoking and Lung Cancerin the Kashmir Valley of the Indian SubcontinentAsian Pacific J Cancer Prev, 12, 519-524; doi.) documented

that hookah smokers were nearly 6-times at risk for development of lung cancer as compared to healthy non-smokers in Kashmir (India). Hookah in Kashmir has some peculiar features in having a direct contact of thelive embers with the burning tobacco thus resulting in high temperatures that augments the production of carcinogenic products from tobacco burning. Additionally water in the hookah base is not changed after everysession that renders the water contaminated to a greater degree and thus a possible source of dissolvedcarcinogens.Snuff

Users of snuff are believed to face less cancer risk than smokers, but are still at greater risk than people whodo not use any tobacco products.[201] They also have an equal risk of other health problems directly linked tonicotine such as increased rate of atherosclerosis.[citation needed ]

Documents

Health Effects of Tobacco