Health effects of tobacco
products, especially when smoked or used orally, have serious negative effects on human health. Smoking and smokeless tobacco use are the single greatest causes of preventable death globally. Half of tobacco users die from complications related to such use. Current smokers are estimated to die an average of 10 years earlier than non-smokers. The World Health Organization estimates that, annually, more than 7 million people die from tobacco-related causes, including 1.6 million non-smokers due to secondhand smoke. It is further estimated to have caused 100 million deaths in the 20th century.
Tobacco smoke contains over 70 chemicals, known as carcinogens, that cause cancer. It also contains nicotine, a highly addictive psychoactive drug. When tobacco is smoked, the nicotine causes physical and psychological dependency. Cigarettes sold in least developed countries have higher tar content and are less likely to be filtered, increasing vulnerability to tobacco smoking-related diseases in these regions.
Tobacco use most commonly leads to diseases affecting the heart, liver, and lungs. Smoking is a major risk factor for several conditions, namely pneumonia, heart attacks, strokes, chronic obstructive pulmonary disease —including emphysema and chronic bronchitis—and multiple cancers. It is also responsible for peripheral arterial disease and high blood pressure. The effects vary depending on how frequently and for how many years a person smokes. Smoking earlier in life and smoking cigarettes with higher tar content increases the risk of these diseases. Additionally, other forms of environmental tobacco smoke exposure, known as secondhand and thirdhand smoke, have manifested harmful health effects in people of all ages. Tobacco use is also a significant risk factor in miscarriages among pregnant women who smoke. It contributes to several other health problems for the fetus, such as premature birth and low birth weight, and increases the chance of sudden infant death syndrome by 1.4 to 3 times. The incidence of erectile dysfunction is approximately 85 percent higher in men who smoke compared to men who do not smoke.
Many countries have taken measures to control tobacco consumption by restricting its usage and sales. They have printed warning messages on packaging. Moreover, smoking bans in public places like workplaces, theaters, bars, and restaurants have been enacted to reduce exposure to secondhand smoke. Tobacco taxation inflating the price of tobacco products, have also been imposed.
In the late 1700s and the 1800s, the idea that tobacco use caused certain diseases, including mouth cancers, was initially accepted by the medical community. In the 1880s, automation dramatically reduced the cost of cigarettes, cigarette companies greatly increased their marketing, and use expanded. From the 1890s onwards, associations of tobacco use with cancers and vascular disease were regularly reported. By the 1930s, multiple researchers concluded that tobacco use caused cancer and that tobacco users lived substantially shorter lives. Further studies were published in Nazi Germany in 1939 and 1943, and one in the Netherlands in 1948. However, widespread attention was first drawn in 1950 by researchers from the United States and the United Kingdom, but their research was widely criticized. Follow-up studies in the early 1950s found that people who smoked died faster and were more likely to die of lung cancer and cardiovascular disease. These results were accepted in the medical community and publicized among the general public in the mid-1960s.
Health effects of smoking
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, 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 nonsmokers. 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 nonsmokers: 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 nonsmokers, 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. This makes it the most common cause of preventable early death. 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. Smokers are three times more likely to die before the age of 60 or 70 than non-smokers.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 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.
According to WHO, 27137 annual deaths are attributed to tobacco use in Nepal.
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. The possible connection between breast cancer and tobacco is still uncertain.Lung cancer
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 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 nonsmokers 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.
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 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.