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The British Doctors' Study was a prospective cohort study which ran from 1951 to 2001, and in 1956 provided convincing statistical evidence that tobacco smoking increases risk of lung cancer. [2]
Although there had been suspicions of a link between smoking and various diseases, the evidence for this link had been largely circumstantial. In fact, smoking had been advertised as "healthy" for many years, and there had been no clear explanation why rates of lung cancer had soared. [3]
To further investigate the link, the Medical Research Council (MRC) instructed its Statistical Research Unit (later the Oxford-based Clinical Trial Service Unit) to conduct a prospective study into the link. This approach to medical questions was fairly new: in the 1954 "Preliminary report", [4] the researchers felt it necessary to offer a definition of the prospective principle.
The study, when it was published in 1956, heralded a new type of scientific research, showed the relevance of epidemiology and medical statistics in questions of public health, and vitally linked tobacco smoking to a number of serious diseases. [5]
In October 1951, the researchers wrote to all registered physicians in the United Kingdom, and obtained responses in two-thirds, 40,701 of them. No further cohorts were recruited. Because of the limited sample size females were excluded from most analyses and publications focused on the male physicians.
The respondents were stratified into decade of birth, sex and their cause-specific mortality, as well as general physical health and current smoking habits, followed up in further questionnaires in 1957, 1966, 1971, 1978, 1991 and finally in 2001.
Response rates were quite high, making appropriate statistical analyses possible. The result was, that both lung cancer and "coronary thrombosis" (the then-prevalent term for myocardial infarction, now commonly referred to as "heart attack") occurred markedly more often in smokers.
In the follow-up reports, published every ten years, more information became available. A major conclusion of the study is, for example, that smoking decreases life span up to 10 years, and that more than 50% of all smokers die of a disease known to be smoking-related, although the excess mortality depends on amount of smoking, specifically, on average, those who smoke until age 30 have no excess mortality, those who smoke until age 40 lose 1 year, those who smoke until 50 lose 4 years, and those who smoke until age 60 lose 7 years. [1]
The true impact of the study is difficult to gauge, as smoking was not considered a public health problem in the 1950s, and the appreciation of the problem would only grow in the ensuing decades. Nevertheless, the British Doctors' Study was to provide conclusive evidence of linkage between smoking and lung cancer, myocardial infarction, respiratory disease and other smoking-related illnesses.
The original study was run by Richard Doll and Austin Bradford Hill. Richard Peto joined the team in 1971 and would, with Doll, prepare all subsequent reports for publication. Doll and Peto are both celebrated epidemiologists, and their fame is largely based on their pioneering work in the study mentioned. They would continue their work on other cardiovascular studies, for example the more recent Heart Protection Study.
The phrase "correlation does not imply causation" refers to the inability to legitimately deduce a cause-and-effect relationship between two events or variables solely on the basis of an observed association or correlation between them. The idea that "correlation implies causation" is an example of a questionable-cause logical fallacy, in which two events occurring together are taken to have established a cause-and-effect relationship. This fallacy is also known by the Latin phrase cum hoc ergo propter hoc. This differs from the fallacy known as post hoc ergo propter hoc, in which an event following another is seen as a necessary consequence of the former event, and from conflation, the errant merging of two events, ideas, databases, etc., into one.
Tobacco smoking is the practice of burning tobacco and ingesting the resulting smoke. The smoke may be inhaled, as is done with cigarettes, or simply released from the mouth, as is generally done with pipes and cigars. The practice is believed to have begun as early as 5000–3000 BC in Mesoamerica and South America. Tobacco was introduced to Eurasia in the late 17th century by European colonists, where it followed common trade routes. The practice encountered criticism from its first import into the Western world onwards but embedded itself in certain strata of a number of societies before becoming widespread upon the introduction of automated cigarette-rolling apparatus.
The BMJ is a weekly peer-reviewed medical journal, published by BMJ Group, which in turn is wholly-owned by the British Medical Association (BMA). The BMJ has editorial freedom from the BMA. It is one of the world's oldest general medical journals. Previously called the British Medical Journal, the title was officially shortened to BMJ in 1988, and then changed to The BMJ in 2014. The journal is published by BMJ Publishing Group Ltd, a subsidiary of the British Medical Association (BMA). The current editor-in-chief of The BMJ is Kamran Abbasi, who was appointed in January 2022.
Passive smoking is the inhalation of tobacco smoke, called passive smoke, secondhand smoke (SHS) or environmental tobacco smoke (ETS), by individuals other than the active smoker. It occurs when tobacco smoke diffuses into the surrounding atmosphere as an aerosol pollutant, which leads to its inhalation by nearby bystanders within the same environment. Exposure to secondhand tobacco smoke causes many of the same diseases caused by active smoking, although to a lower prevalence due to the reduced concentration of smoke that enters the airway. The health risks of secondhand smoke are a matter of scientific consensus, and have been a major motivation for smoking bans in workplaces and indoor venues, including restaurants, bars and night clubs, as well as some open public spaces.
A case–control study is a type of observational study in which two existing groups differing in outcome are identified and compared on the basis of some supposed causal attribute. Case–control studies are often used to identify factors that may contribute to a medical condition by comparing subjects who have the condition with patients who do not have the condition but are otherwise similar. They require fewer resources but provide less evidence for causal inference than a randomized controlled trial. A case–control study is often used to produce an odds ratio. Some statistical methods make it possible to use a case-control study to also estimate relative risk, risk differences, and other quantities.
Sir Austin Bradford Hill was an English epidemiologist who pioneered the modern randomised clinical trial and, together with Richard Doll, demonstrated the connection between cigarette smoking and lung cancer. Hill is widely known for pioneering the "Bradford Hill" criteria for determining a causal association.
Sir William Richard Shaboe Doll was a British physician who became an epidemiologist in the mid-20th century and made important contributions to that discipline. He was a pioneer in research linking smoking to health problems. With Ernst Wynder, Bradford Hill and Evarts Graham, he was credited with being the first to prove that smoking increased the risk of lung cancer and heart disease.
The Framingham Heart Study is a long-term, ongoing cardiovascular cohort study of residents of the city of Framingham, Massachusetts. The study began in 1948 with 5,209 adult subjects from Framingham, and is now on its third generation of participants. Prior to the study almost nothing was known about the epidemiology of hypertensive or arteriosclerotic cardiovascular disease. Much of the now-common knowledge concerning heart disease, such as the effects of diet, exercise, and common medications such as aspirin, is based on this longitudinal study. It is a project of the National Heart, Lung, and Blood Institute, in collaboration with Boston University. Various health professionals from the hospitals and universities of Greater Boston staff the project.
Sir Richard Peto is an English statistician and epidemiologist who is Professor of Medical Statistics and Epidemiology at the University of Oxford, England.
Tobacco products, especially when smoked or used orally, have negative effects on human health, and concerns about these effects have existed for a long time. Research has focused primarily on cigarette smoking.
Tobacco harm reduction (THR) is a public health strategy to lower the health risks to individuals and wider society associated with using tobacco products. It is an example of the concept of harm reduction, a strategy for dealing with the use of drugs. Tobacco smoking is widely acknowledged as a leading cause of illness and death, and reducing smoking is vital to public health.
Smoking is a practice in which a substance is combusted and the resulting smoke is typically inhaled to be tasted and absorbed into the bloodstream of a person. Most commonly, the substance used is the dried leaves of the tobacco plant, which have been rolled with a small rectangle of paper into an elongated cylinder called a cigarette. Other forms of smoking include the use of a smoking pipe or a bong.
Tobacco was long used in the early Americas. The arrival of Spain introduced tobacco to the Europeans, and it became a lucrative, heavily traded commodity to support the popular habit of smoking. Following the Industrial Revolution, cigarettes became hugely popular worldwide. In the mid-20th century, medical research demonstrated severe negative health effects of tobacco smoking including lung and throat cancer, which led to a sharp decline in tobacco use.
A Frank Statement to Cigarette Smokers was a historic first advertisement in a campaign run by major American tobacco companies on January 4, 1954, to create doubt by disputing recent scientific studies linking smoking cigarettes to lung cancer and other dangerous health effects.
The history of smoking dates back to as early as 5000 BC in the Americas in shamanistic rituals. With the arrival of the Europeans in the 16th century, the consumption, cultivation, and trading of tobacco quickly spread. The modernization of farming equipment and manufacturing increased the availability of cigarettes following the reconstruction era in the United States. Mass production quickly expanded the scope of consumption, which grew until the scientific controversies of the 1960s, and condemnation in the 1980s.
Geoffrey C. Kabat is an American epidemiologist, cancer researcher, and author. He has been on the faculty of the Albert Einstein College of Medicine and State University of New York, Stony Brook. He was co-author of a discredited BMJ study funded by the tobacco industry, that erroneously said there was no association between secondhand smoke and health problems.
Takeshi Hirayama was a Japanese cancer epidemiologist and anti-tobacco activist who served as the chief of the epidemiology division at the National Cancer Center in Tokyo from 1965 until 1985. He has been credited with publishing the first study linking passive smoking to lung cancer, and also conducted research on the relationship between certain dietary factors and cancer.
The Center for Indoor Air Research was a tobacco industry front group established by three American tobacco companies—Philip Morris, R.J. Reynolds, and Lorillard—in Linthicum, Maryland, in 1988. The organization funded research on indoor air pollution, some of which pertained to passive smoking and some of which did not. It also funded research pertaining to causes of lung cancer other than passive smoking, such as diet. The organization disbanded in 1998 as a result of the Tobacco Master Settlement Agreement.
Horace Joules LRCP, MRCP, MRCS, FRCP was a British physician, health administrator and health campaigner, who played an important role in promoting public health and preventative medicine; particularly the link between cigarette smoking and lung cancer following the work of Richard Doll, Austin Bradford Hill, Ernst Wynder and Evarts Graham, and the adverse effects of air pollution.
Smoker’s macrophages are alveolar macrophages whose characteristics, including appearance, cellularity, phenotypes, immune response, and other functions, have been affected upon the exposure to cigarettes. These altered immune cells are derived from several signaling pathways and are able to induce numerous respiratory diseases. They are involved in asthma, chronic obstructive pulmonary diseases (COPD), pulmonary fibrosis, and lung cancer. Smoker’s macrophages are observed in both firsthand and secondhand smokers, so anyone exposed to cigarette contents, or cigarette smoke extract (CSE), would be susceptible to these macrophages, thus in turns leading to future complications.
