The British Doctors' Study was a prospective cohort study which ran from 1951 to 2001, and in 1956 provided convincing statistical proof that tobacco smoking increased the risk of lung cancer.
A prospective cohort study is a longitudinal cohort study that follows over time a group of similar individuals (cohorts) who differ with respect to certain factors under study, to determine how these factors affect rates of a certain outcome. For example, one might follow a cohort of middle-aged truck drivers who vary in terms of smoking habits, to test the hypothesis that the 20-year incidence rate of lung cancer will be highest among heavy smokers, followed by moderate smokers, and then nonsmokers.
Tobacco smoking is the practice of smoking tobacco and inhaling tobacco smoke. 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.
Lung cancer, also known as lung carcinoma, is a malignant lung tumor characterized by uncontrolled cell growth in tissues of the lung. This growth can spread beyond the lung by the process of metastasis into nearby tissue or other parts of the body. Most cancers that start in the lung, known as primary lung cancers, are carcinomas. The two main types are small-cell lung carcinoma (SCLC) and non-small-cell lung carcinoma (NSCLC). The most common symptoms are coughing, weight loss, shortness of breath, and chest pains.
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.
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",the researchers felt it necessary to offer a definition of the prospective principle.
Oxford is a university city in south central England and the county town of Oxfordshire. With a population of approximately 155,000, it is the 52nd largest city in the United Kingdom, with one of the fastest growing populations in the UK, and it remains the most ethnically diverse area in Oxfordshire county. The city is 51 miles (82 km) from London, 61 miles (98 km) from Bristol, 59 miles (95 km) from Southampton, 57 miles (92 km) from Birmingham and 24 miles (39 km) from Reading.
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.
Epidemiology is the study and analysis of the distribution and determinants of health and disease conditions in defined populations.
Medical statistics deals with applications of statistics to medicine and the health sciences, including epidemiology, public health, forensic medicine, and clinical research. Medical statistics has been a recognized branch of statistics in the United Kingdom for more than 40 years but the term has not come into general use in North America, where the wider term 'biostatistics' is more commonly used. However, "biostatistics" more commonly connotes all applications of statistics to biology. Medical statistics is a subdiscipline of statistics. "It is the science of summarizing, collecting, presenting and interpreting data in medical practice, and using them to estimate the magnitude of associations and test hypotheses. It has a central role in medical investigations. It not only provides a way of organizing information on a wider and more formal basis than relying on the exchange of anecdotes and personal experience, but also takes into account the intrinsic variation inherent in most biological processes."
Public health has been defined as "the science and art of preventing disease, prolonging life and promoting human health through organized efforts and informed choices of society, organizations, public and private, communities and individuals". Analyzing the health of a population and the threats it faces is the basis for public health. The public can be as small as a handful of people or as large as a village or an entire city; in the case of a pandemic it may encompass several continents. The concept of health takes into account physical, psychological and social well-being. As such, according to the World Health Organization, it is not merely the absence of disease or infirmity.
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.
Myocardial infarction (MI), commonly known as a heart attack, occurs when blood flow decreases or stops to a part of the heart, causing damage to the heart muscle. The most common symptom is chest pain or discomfort which may travel into the shoulder, arm, back, neck, or jaw. Often it occurs in the center or left side of the chest and lasts for more than a few minutes. The discomfort may occasionally feel like heartburn. Other symptoms may include shortness of breath, nausea, feeling faint, a cold sweat, or feeling tired. About 30% of people have atypical symptoms. Women more often present without chest pain and instead have neck pain, arm pain, or feel tired. Among those over 75 years old, about 5% have had an MI with little or no history of symptoms. An MI may cause heart failure, an irregular heartbeat, cardiogenic shock, or cardiac arrest.
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.
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.
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 caused lung cancer and increased the risk of heart disease. He also carried out pioneering work on the relationship between radiation and leukemia as well as that between asbestos and lung cancer, and alcohol and breast cancer. On 28 June 2012 he was the subject of a series on Radio Four called The New Elizabethans, a programme broadcast to mark the Diamond Jubilee of Queen Elizabeth II, dealing with 60 public figures from her reign.
Sir Austin Bradford Hill FRS, English epidemiologist and statistician, pioneered the randomized 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 Richard Peto is Professor of Medical Statistics and Epidemiology at the University of Oxford, England.
The BMJ is a weekly peer-reviewed medical journal. It is one of the world's oldest general medical journals. Originally 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 the global knowledge provider BMJ, a wholly owned subsidiary of the British Medical Association. The editor in chief of The BMJ is Fiona Godlee, who was appointed in February 2005.
Passive smoking is the inhalation of smoke, called second-hand smoke (SHS), or environmental tobacco smoke (ETS), by persons other than the intended "active" smoker. It occurs when tobacco smoke permeates any environment, causing its inhalation by people within that environment. Exposure to second-hand tobacco smoke causes disease, disability, and death. The health risks of second-hand smoke are a matter of scientific consensus. These risks have been a major motivation for smoke-free laws in workplaces and indoor public places, 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 that condition/disease with patients who do not have the condition/disease but are otherwise similar. They require fewer resources but provide less evidence for causal inference than a randomized controlled trial. We only get odds ratio from a case–control study which is an inferior measure of strength of association as compared to relative risk.
The Framingham Heart Study is a long-term, ongoing cardiovascular cohort study on 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 it 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.
Excessive alcohol intake is associated with an elevated risk of alcoholic liver disease (ALD), heart failure, some cancers, and accidental injury, and is a leading cause of preventable death in industrialized countries. However, extensive research has shown that moderate alcohol intake is associated with health benefits, including less cardiovascular disease, diabetes, and hypertension.
Tobacco use has predominantly negative effects on human health and concern about health effects of tobacco has a long history. Research has focused primarily on cigarette tobacco 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 abuse of other drugs. Tobacco smoking is widely acknowledged as a leading cause of illness and death, and preventing smoking is vital to public health.
Smoking is a practice in which a substance is burned and the resulting smoke breathed in to be tasted and absorbed into the bloodstream. Most commonly the substance is the dried leaves of the tobacco plant which have been rolled into a small square of rice paper to create a small, round cylinder called a "cigarette". Smoking is primarily practiced as a route of administration for recreational drug use because the combustion of the dried plant leaves vaporizes and delivers active substances into the lungs where they are rapidly absorbed into the bloodstream and reach bodily tissue. In the case of cigarette smoking these substances are contained in a mixture of aerosol particles and gasses and include the pharmacologically active alkaloid nicotine; the vaporization creates heated aerosol and gas into a form that allows inhalation and deep penetration into the lungs where absorption into the bloodstream of the active substances occurs. In some cultures, smoking is also carried out as a part of various rituals, where participants use it to help induce trance-like states that, they believe, can lead them to spiritual enlightenment.
Tobacco has a long history from its usages in the early Americas. It increased in popularity with the arrival of Spain to America, which introduced tobacco to the Europeans by whom it was heavily traded. Following the industrial revolution, cigarettes were becoming popularized in the New World as well as Europe, which fostered yet another unparalleled increase in growth. This remained so until scientific studies in mid 20th century demonstrated the negative health effects of tobacco smoking including lung and throat cancer.
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.
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 non-profit organization 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.
The 1950 Wynder and Graham Study was conducted by Ernest Wynder and Evarts Graham and was entitled "Tobacco Smoking as a Possible Etiologic Factor in Bronchiogenic Carcinoma: A Study of Six Hundred and Eighty-Four Proved Cases". It was published on May 27, 1950. It was a case-control study to determine the relationship between various external factors and the development of bronchogenic carcinoma. The study concluded that long-term tobacco usage contributes to the onset of lung cancer, as an overwhelming majority (96.5%) of the men with the disease were classified as moderate to heavy smokers for an extended period of time, compared to a lower percentage of the general hospital population control group.