Smoking is the most important preventable cause of death.
People who smoke have a 2-3-fold risk of premature death compared with those who do not smoke Smoking and Total Mortality. Women are more susceptible to tobacco-induced diseases than men.
In a study performed among British male doctors, the probability of dying in the middle age (45-64 years) was 3-fold and in the retired age (65-84 years) 2-fold among smokers compared to those who had never smoked. The increase in risk is correlated to the quantity of cigarettes and duration of smoking. The risk diminishes after stopping smoking Reduction of Cardiovascular Risk after Stopping Smoking. Smoking shortens the lifespan by 10 years; quitting at the age of 60, 50, 40 or 30 increases life expectancy by 3, 6, 9 or 10 years, respectively, compared to those who continue smoking.
The risk of lung cancer is on average about 6- to 21-fold, and it rises with increased consumption of cigarettes. 90% of lung cancers are caused by smoking.
The risk of cancer of mouth, pharynx, pancreas or oesophagus is 6- to 8-fold.
Smoking also increases the risk of other cancers to 1.5- to 3-fold (cancer of urinary bladder, kidney, stomach, liver, colon or cervix; leukaemia).
The risk of myocardial infarction and cerebral and peripheral vascular diseases increases by 50%, and it increases in a dose-dependent way. In persons less than 60 years of age, the risk of ischaemic heart disease is 2- to 5.5-fold and the risk of cerebral infarction is 3- to 4-fold.
Passive smoking increases the risk of lung cancer by approximately 25%. The risk of lung cancer has also been shown at the individual level.
The risk of coronary events at the population level is 25-30% higher compared with non-exposed indivuals. The risk of all persons exposed to environmental tobacco smoke is about half of the additional risk that active smokers have. The risk is dose-dependent, i.e. it grows with increasing exposure. The risk has not been proven at the individual level as it has been for lung cancer.
The increased risk of stroke appears to be of a similar magnitude as that of coronary artery disease.
Exposure causes inflammatory changes in the respiratory tract and suppresses the immune response and function of the pulmonary epithelium cilia, leading to increased susceptibility to respiratory infections and possibly also to asthma and COPD.
In children, exposure increases susceptibility to respiratory infections and otitides as well as the risk of onset and exacerbation of asthma.
Other harmful effects of smoking
Nicotine causes strong dependence that can be compared to that of narcotic substances.
Smoking can alter the clinical effects of various drugs. Proton pump inhibitors prevent recurrence of ulcer much less in smokers than in those who do not smoke. Smoking decreases the efficacy of angina pectoris medication and diuretics. Tobacco smoke induces CYP1A2 activity and thus accelerates the metabolism of certain pharmacological agents: heparin, warfarin, theophylline, flecainide, propranolol, benzodiazepines, chlordiazepoxide, haloperidol, clozapine, olanzapine and estradiol. Smoking reduces cutaneous superficial circulation thus decreasing the absorption of subcutanously injected insulin.
Snuff (smokeless tobacco)
Contains carcinogenic nitrosamines.
Increases the risk of cancer in the oral cavity, oesophagus and pancreas.
The risk of fatal myocardial infarction and stroke is increased.
In electronic cigarettes, propylene glycol or glycerol liquid is heated up with a battery. The vapour contains carcinogenic agents (polycyclic aromatic hydrocarbon compounds, among others) and sometimes also silicate and metal particles. The use of electronic cigarette containing nicotine causes strong dependence. Electronic cigarettes interfere with pulmonary function and increase the risk of cardiovascular diseases, but knowledge of long-term effects is insufficient.
In 2019, electronic cigarette use associated lung injury (e-cigarette or vaping product use associated lung injury [EVALI]) and deaths were found in the United Sates. In addition to the symptoms of respiratory passages and gastrointestinal tract, fever and other general symptoms appeared. In the majority of the cases, tetrahydrocannabinol and vitamin E acetate was found in the used product.
People passively exposed to e-cigarette vapour show blood nicotine concentrations that may be as high as those found in people exposed to tobacco smoke.
References
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National Cancer Institute (NCI) & Centers for Disease Control and Prevention (CDC) (2014) Smokeless Tobacco and Public Health: A Global Perspective. Bethesda, MD: U.S. Department of Health and Human Services, Centers for Disease Control and Prevention and National Institutes of Health, National Cancer Institute. NIH Publication No. 14-7983; 2014.http://cancercontrol.cancer.gov/brp/tcrb/smokeless-tobacco