House of Commons - Health - Minutes of Evidence

Select Committee on Health Minutes of Evidence

Memorandum by British American Tobacco

THE TOBACCO INDUSTRY AND THE HEALTH RISKS OF SMOKING (TB 28)

RELATIVE RISK AND AMOUNT SMOKED

292. While, as described above, both the Government and the tobacco companies have focused on product modifications that might reduce the risk of smoking, it is also important to consider other factors that may affect the risks of smoking. One such factor is the amount smoked.

293. The relationship between smoking and disease when looking at human populations is predominately described by epidemiological studies. These typically report lower smoking-related relative risks in groups that smoke fewer cigarettes for fewer years compared to those who smoke more. However, such studies report increases in risk for groups who smoke relatively little compared to those that do not smoke at all, and the only way to be certain of avoiding smoking-related risks is not to smoke (US Department of Health and Human Services, "Reducing the Health Consequences of Smoking: 25 Years of Progress, A Report of the Surgeon General", 1989).

294. Moderate, as opposed to excessive, behaviour is an often recommended common-sense approach to everyday activities for most people. Moderate use of many consumer products with associated health risks, such as alcohol or fatty foods, may reduce or even eliminate risks. Smoking less does reduce the risks associated with smoking as determined in groups of people, but only in the context of there being no clearly defined risk-free level.

Statistical studies on smoking and health

295. The World Health Organisation's International Agency for Research into Cancer (IARC) recently stated:

"Epidemiology is the only source of direct scientific evidence about the exposure effects and the preventability of disease within a human population. Laboratory scientists have identified carcinogenic compounds in tobacco smoke and have been able to produce respiratory cancers in experimental animals by forcing them to inhale cigarette smoke. However, the argument that cigarette smoking causes lung cancer in humans would remain unconvincing if epidemiologists had not also demonstrated that lung cancer occurs much more often in smokers than in non-smokers." (Dos Santos Silva J, "Cancer Epidemiology: Principles and Methods", IARC WHO, p 3, 1999).

296. There are different types of epidemiological study, but most rely on questionnaires to collect information on groups of people (Beaglehold, R Bonita, R and Kjellstrom, T "Basic Epidemiology", WHO, p 31-54, 1994). For smoking and health, the studies in their broadest sense compared the incidence of diseases in a group of smokers with that in groups of non-smokers. Many studies have asked people detailed questions about smoking habits, including how many cigarettes were smoked, when did someone start and stop smoking, what type of cigarette was smoked, and even did the person inhale or not (Wu-Williams A and Samet JM, "Epidemiology of Lung Cancer, Lung Biology", Health and Disease, Volume 74, JM Samet, Marcel Dekker Inc, 1994). The questionnaires often will provide averaged recollections over many decades of smoking (Beaglehole et al, ibid).

297. The studies most often applied to smoking and health report relative risks. A relative risk quantifies the difference in the incidence of disease in one group compared to another (Beaglehole et al, ibid). A relative risk of 15 for smoking and lung cancer means that the group of smokers in the study had 15 times the incidence of lung cancer than the group of non-smokers. Such numbers average across many different smoking histories, and may not reflect whether a sub-group, such as life-time heavy smokers, have much higher relative risks than others.

298. Epidemiology cannot determine what will happen to an individual. As IARC note, ". . . epidemiology is concerned with events that occur in populations: the primary units of concern are groups of people, not separate individuals. This is what differentiates epidemiology from clinical medicine." (Dos Santos Silva et al, ibid, p 2) Epidemiology is useful in providing a broad brush picture of what happens to groups of people who adopted various smoking habits. It can not be used to determine what will happen to any individual.

299. Richard Peto and Sir Richard Doll explained the limits of epidemiology in relation to individuals in a letter to the British Medical Journal, stating, "Consider, for example, 1,000 habitual smokers who die of myocardial infarction at about 65 years of age. Even though the epidemiologist may be able to say with confidence that about half of these 1,000 deaths were due to tobacco, there would be no way for medical practitioners certifying those deaths to know which ones to attribute to the habit. Should all be attributed, should none be attributed, or should about half be attributed—and, if half, which ones?" (Peto R and Doll R, "Smoking Accepted on Death Certificates", British Medical Journal, 305, p 829, 1992).

300. There are many diseases associated with smoking, as described, among others, by the reports of US Surgeon Generals over the years, the Royal College of Physicians and the ISCSH. Much of the statistical research, particularly the larger studies, has focused on cancer, and particularly lung cancer, emphysema and chronic bronchitis (often combined under the term chronic obstructive pulmonary disease ("COPD")) and heart disease.

301. Lung cancer: Smoking is strongly associated with lung cancer incidence. Statistical studies have typically reported a dose-response relationship between the amount smoked and the strength of the lung cancer relative risk. The relative risks for lung cancer have been associated primarily with the number of cigarettes smoked per day and the number of years smoking. These two parameters can affect the relative risks dramatically. For example, an American Cancer Society study (CPS-II) reported lung cancer relative risks of around three for women smoking between one and 10 cigarettes for between 21 and 30 years, and a relative risk of around 39 for women smoking over 31 cigarettes per day for between 41 and 70 years—both compared to non-smokers (Wu-Williams A and Samet JM, ibib). With an annual non-smoker lung cancer mortality rate of around five per 100,000, this would mean a rate of 15 per 100,000 in the group that smoked less than 10 cigarettes for less than 30 years and 195 per 100,000 in the heavy smokers.

302. The studies consistently report much higher lung cancer relative risks for higher consumption per day. For example, the British Doctor's study reported relative risks of eight for men smoking between one and 14 cigarettes per day compared to 25 for smoking more than 25 cigarettes per day. For women in the same study the relative risks for the same categories were 1.3 and 30 respectively (Wu-Williams A and Samet JM, "Epidemiology of Lung Cancer", Marcel Dekker Inc, p 71, 1994).

303. A few studies have also considered inhalation by the smoker. Such investigations rely upon an individual's subjective report of inhalation patterns over a long history of smoking. Several studies have reported higher risks for smokers who inhaled deeply, particularly in groups of people who smoked few cigarettes per day (Wu-Williams A and Samet JM, ibid).

304. COPD: Smoking is also strongly associated with the incidence of chronic bronchitis and emphysema, and the statistical studies have typically dose-response relationships. The US Surgeon General reviewed the data in 1984 concluding that the risk of death from COPD increased with early age of initiation, numbers of cigarettes smoked per day and the depth of inhalation (US Department of Health and Human Services, "The Health Consequences of Smoking, Cardiovascular Disease", A Report of the Surgeon General", p 119, 1983).

305. Duration of smoking also affects the relative risks. One Japanese study reported slightly higher risks for those starting to smoke before age 19 compared to those starting later than age 19 (US Department of Health and Human Services, "The Health Consequences of Smoking. Chronic Obstructive Lung Disease", A Report of the Surgeon General, p 185-216, 1984).

306. The US Surgeon General stated that "Cessation of smoking eventually leads to a decreased risk of mortality from [COPD] compared with that of continuing smokers. The residual excess risk of death for the ex-smoker is directly proportional to the overall lifetime exposure to cigarette smoke and to the total number of years since one quit smoking. However, the risk of [COPD] mortality among former smokers does not decline to equal that of the never smoker, even after 20 years of cessation." (US Department of Health and Human Services, ibid, p 214, 1984).

307. Heart disease: Heart disease is the leading cause of death in many developed countries. There are many identified risk factors, with most public health authorities focusing on smoking, cholesterol, lack of exercise, obesity and hypertension. The relative risks relating smoking to heart disease are much lower than for lung cancer and COPD. This, in combination with the many risk factors involved, makes the analysis of risks associated with smoking alone, and how they vary with lifetime smoking behaviour, quite difficult to determine with any certainty.

308. The 1983 US Surgeon General's report looked extensively at heart disease. Some of the larger prospective studies provide data on smoking and coronary heart disease by amount smoked. Most report a dose-response relationship. Numbers of cigarettes smoked per day are associated with the relative risk of coronary heart disease ("CHD") in most studies.

309. The British Doctors' study reported male relative risks for CHD of 1.47 for 1-14 cigarettes, 1.58 for 15-24 cigarettes and 1.92 for more than 25 cigarettes per day. The American Cancer Society 9-state study reported 1.29 male relative risk for CHD for 1-9 cigarettes, 1.89 for 10-20 cigarettes, 2.15 for 21-40 cigarettes and 2.41 for more than 40 cigarettes (US Department of Health and Human Services, ibid, p 63-156, 1983).

310. Some studies have also looked at inhalation characteristics. The British Doctors study reported relative risks for CHD in males of 2.2 for inhalers and 1.2 for non-inhalers. The US Surgeon General reported that "a clear dose response relationship has been demonstrated for the number of cigarettes smoked per day, depth of inhalation, age of initiation of the smoking habit, and total duration of the smoking habit. The risk of coronary disease mortality is lower with fewer cigarettes smoked per day, but the evidence presented in the prospective mortality studies does not suggest a threshold for this effect. There is no evidence to suggest that any level of cigarettes smoking is safe with regard to coronary heart disease." (US Department of Health and Human Services, ibid, p 119, 1983).

Public health views of moderate smoking

311. For the last 40 years and more, public health authorities have warned about the dangers of smoking and advised people not to smoke. Advice to those who decide to continue to smoke has varied.

312. Early pronouncements by the UK Minister of Health made in 1954 were reported as "Mr. Macleod gave this special warning to young people. Avoid heavy smoking, especially of cigarettes. Five a day seems to be a safe limit." ("The Startling Facts. Cigarettes and You. Are 5 a Day a Safe Limit?", The Daily Sketch, London, 13 February, 1954). This was later replaced by the message that there was no "safe" limit to smoking.

313. In 1957, the US Surgeon General stated that "The Public Health Service feels the weight of the evidence is increasingly pointing in one direction; that excessive smoking is one of the causative factors in lung cancer." (US Department of Health and Human Services, "Reducing the Health Consequences of Smoking, 25 Years of Progress", p 5, 1989). In 1966, the Surgeon General, along with many other public health authorities around the world, suggested that smokers who do not quit should switch to lower tar cigarettes. In that year the Public Health Service said, "the preponderance of scientific evidence strongly suggests that the lower the tar and nicotine content of cigarette smoke, the less harmful would be the effect." (US Public Health Service, "Smoking and Health. The Health Consequences of Smoking", 1968 Supplement to the 1967 Health Service Review, 1968). The 1968 US Surgeon General's Report estimated smoking-related loss of life expectancy among young men as eight years for "heavy" smokers (over two packs a day) and four years for "light" smokers (less than ½ pack per day)(US Public Health Service, "Smoking and Health. The Health Consequences of Smoking", Public Health Service Review, Supplement, 1968).

314. In 1975, the World Health Organisation, considering international tobacco control, recommended to governments that: "every cigarette packet could include a card giving rules for less dangerous smoking, for example:

— Smoke fewer cigarettes;

— Inhale less frequently and less deeply;

— Take fewer puffs from each cigarette;

— Remove the cigarette from the mouth between puffs;

— Smoke cigarettes with a low tar and nicotine content."

(WHO, "Smoking and its Effects on Health", Technical Report Series 568, WHO, Geneva, p 80, 1975)

315. In 1981, the Surgeon General's report on "The Changing Cigarette" noted that the overall judgement was unchanged from 1966: "smokers who are unwilling or as yet unable to quit are well advised to switch to cigarettes yielding less `tar' and nicotine, provided they do not increase their smoking or change their smoking in other ways. But our review raises new questions and suggests an even more cautious approach to the issue." (US Surgeon General, "The Health Consequences of Smoking: The Changing Cigarette", p v, 1981).

316. In the 1980s the US and the UK public health authorities took quite separate paths. In 1982, as described fully above, the UK initiated the Tobacco Products Research Trust (TPRT) on the recommendation of the ISCSH. The UK's product modification programme aimed at encouraging smokers to switch to lower tar products. Eventually European legislation required tar and nicotine yields to be printed on packs and progressively limiting the maximum tar delivery to 12 mg per cigarette.

317. In contrast to the UK approach, the US authorities did not actively encourage lower tar products in the same manner, and to date there is no limit on the amount of tar that a cigarette sold in the US can yield, nor any requirement for printing tar and nicotine yield on packs, though this was required in advertising. Despite this, the consumer trend in the US is very substantially towards cigarettes with lower tar and lower nicotine yields.

318. The US Federal Trade Commission at the end of 1998 disavowed itself from the FTC method of measuring tar and nicotine yields of cigarettes, on the basis that it may not accurately reflect the amount of smoke that smokers take in—especially smokers of lower tar products, in the light of evidence about compensation. Although the limitations of the method in this respect had been known for some time, the FTC proposed an education campaign to warn consumers to be sceptical of the significance that such yield ratings may have, noting specifically: "There is no such thing as a safe smoke, no matter what the `tar' and nicotine ratings are; and people who are concerned about the health effects of smoking should quit" (FTC, "Report of Tar", Nicotine, and Carbon Monoxide of Smoke of 1252 Varieties of Domestic Cigarettes for the Year 1997", p 2, 1999).

319. This hypothesis that tar and nicotine yields provide poor information has not been generally adopted outside of the US, and many regulatory authorities continue to adopt the International Standards Organisation's method of measuring tar and nicotine, and require manufacturers to print tar and nicotine on packs and in many cases have set limits on maximum tar content.

320. In 1996, the American Council on Science stated: "While it is possible that just a few cigarettes a day might not present a significant health risk to most people, there are relatively few smokers who limit their smoking that much. The vast majority of current smokers smoke more than 15 cigarettes a day—clearly a level that dramatically increases the risk of many diseases." (Napier N, London WM, Whelan EM and Golaine Case A, "Cigarettes: What the Warning Label Doesn't Tell You", American Council on Science and Health, p ix, 1996).

The role of the Government in providing information to smokers

321. Public health authorities have for decades provided public education on the risks of smoking. Historically this has included practical advice to smokers who decide to continue smoking despite advice to quit completely. However, much of the current debate focuses on a shift from high to low tar, rather than a general shift from smoking more to smoking less. The epidemiological data continues to suggest that groups of people smoking fewer cigarettes for fewer years have a lower incidence of smoking related diseases than groups smoking more cigarettes for longer.

322. The dose-response relationships in the epidemiology also suggest that the continued public health support of lower tar programmes is probably a sensible approach. Data generally suggests that low tar cigarette smokers, if they smoke the same number of cigarettes for the same period of time, take less tar than smokers of high tar cigarettes.

323. The only choice for those wishing to be certain of avoiding smoking related risks is not to smoke, and the risks for moderate smokers are still higher than for non-smokers. However, for those who choose to smoke, groups that smoke fewer cigarettes for fewer years will be exposed to less risk than those that smoke more for a longer period.

324. British American Tobacco understands that some public health authorities would be concerned about recommending smoking less to those who choose to continue to smoke for fear that such recommendation would result in fewer people quitting. However, we take the view that the Government should seriously consider, in light of the epidemiological data, whether advice other than simply to quit should be given to smokers.



© Parliamentary copyright 2000	Prepared 28 February 2000

Search