APPENDIX 14
Memorandum by the Medical Research Council
(TB 29)
INTRODUCTION
1. The MRC welcomes the opportunity to contribute
to this inquiry. We note that its central focus is the "action
that the tobacco industry has taken, and is currently taking,
in response to the scientific knowledge of the harmful effects
of smoking and the addictive nature of nicotine". Our response
therefore takes the form of a brief commentary on the research
that has been funded by MRC and others, and the evidence it has
produced. For the benefit of the inquiry we have indicated where
the principal areas of concern lie with respect to the harmful
effects of smoking or the addictive nature of nicotine, but would
refer the Inquiry to the report of the Scientific Committee on
Tobacco and Health (1998) where these are summarised in greater
detail. We have provided an overview of the breadth of biomedical
research that has been funded, and continues to be funded, by
the MRC in the areas of the harmful effects of smoking and the
addictive nature of nicotine.
HISTORICAL PERSPECTIVE
2. An association between smoking and cancer
was first noted at the end of the 18th century, and a number of
studies drew conclusions on this correlation up until the early
part of this century. Widely accepted evidence of a causal link
began to emerge in the late 1940s with the early retrospective
case-control studies carried out by the MRC on lung cancer patients.
3. In 1947 Professors Sir Richard Doll and
Sir Austin Bradford Hill began research, funded by the MRC, into
the causes of lung cancer. Their report, published in 1950, detailed
the first evidence that smoking was a major cause of mortality.
In a statement entitled Tobacco smoking and cancer of the lung,
it was concluded that "a major part of the increase (in UK
lung cancer death rates over the previous 25 years) is associated
with tobacco smoking (...) the most reasonable interpretation
of this evidence is that the relationship is one of direct cause
and effect".
4. This early investment by the MRC into
research on the effects of smoking has continued to the present
day. The association between smoking and other disease—such
as coronary disease—has been the focus of much of the more
recent research into smoking, including some very large population
studies. Epidemiological research has also been continuing over
the years, and has benefited from the possibility of prospectively
following people who have been smoking for much of their lives.
One particularly large study, covering a million individuals,
was carried out in the USA, concluding in the 1990s.
5. Much of the early work on the effects
of tobacco smoke was observational (ie epidemiological studies),
leading to questions as to whether proof of causation had been
demonstrated. However, this body of research was also complemented
by experimental demonstration, which led to a wide acceptance
of causality between smoking and lung cancer, chronic bronchitis
and to a certain extent, other diseases.
CURRENT KNOWLEDGE
OF HEALTH
EFFECTS
6. Tobacco smoke is a complex mixture of
many thousands of structurally diverse components. A number of
its constituents are known to be carcinogenic. Cigarette smoking
has been associated with a wide-range of diseases of causes of
death, with most of the associations considered to be causal rather
than coincidental.
7. It has been estimated that smoking kills
about two million people a year in developed countries, half in
middle age (35-69) and half in old age. Over the next 40 years,
should current trends continue, the annual number of deaths from
tobacco smoking could increase to more than 10 million annually.
In the UK smoking is the single largest cause of preventable illness
and early death. It is believed to be responsible for up to 1
in 6 deaths. Smoking related illnesses cost the NHS up to £1.7
billion annually.
8. Recent cohort studies undertaken in various
parts of the world suggest that the following major diseases are
more prevalent among smokers.
— Cancers of mouth, pharynx and larynx
— Cancer of oesophagus
— Cancer of lung
— Cancer of pancreas
— Cancer of bladder
— Ischaemic heart disease
— Hypertension
— Heart Disease (inc. myocardial degeneration, pulmonary
heart disease and other heart disease)
— Aortic anuerysm
— Peripheral vascular disease
— Arteriosclerosis
— Cerebral vascular disease
— Chronic bronchitis and emphysema
— Asthma
— Pneumonia and other respiratory disease
— Peptic ulcer.
9. There is less robust evidence which suggests
that tobacco smoking may be associated with other illnesses as
well such as cancer of the lip, nose, stomach and kidney; myeloid
leukaemia; Crohn's disease; osteoporosis; periodontits; tobacco
ambylopia; age-related macular degeneration; reduced fecundity.
Recent studies also indicate that maternal smoking results in
low infant birth weights and an increase in perinatal mortality.
Tobacco smoking may also be linked to an increased risk of cataracts,
impotence, reduced production of sperm, and increased risk of
cancer in children arising out of mutations produced in the father's
gonads.
10. Some diseases appear to occur less often
than expected in smokers and this may indicate that the chemicals
in tobacco smoke serve to alleviate or prevent them. These include
Parkinson's disease; ulcerative colitis; cancer of body of uterus;
fibroids; nausea and vomiting during pregnancy; pre-eclampsia;
Alzheimer's disease. But these effects are small and cannot be
said to in any way counterbalance the harmful effects of smoking.
11. It is widely accepted that most people
use tobacco to obtain the effects of nicotine, and that nicotine
is an addictive drug that supports dependence processes with many
similarities to those involved in classical drug addictions. No
medications have been developed successfully to treat nicotine
dependence.
12. The possibility that tobacco smoke might
have an effect on the non-smoker as well as the smoker was first
considered in 1928. Several studies undertaken subsequently have
suggested that children face increased risks of bronchitis, pneumonia,
asthma, middle-ear infections and sudden infant death syndrome
as a result of exposure to tobacco smoke arising from smoking
by their parents, for example. There is less substantial evidence
for the effects of "passive smoking" on adults, though
over the last two decades there have been studies showing increased
risks of lung cancer, chronic respiratory disease and myocardial
infarction arising out of non-smoker's exposure to other people's
smoke.
13. It is commonly accepted that the ill-health
effects of tobacco smoking are greatest among the poorer sections
of the community. This may be due to greater consumption of cigarettes
among lower socio-economic groups or to greater risk caused by
other social and behavioural factors. Tobacco smoking is one of
the principal contributors to inequalities in health in UK society.
14. Smoking is on the increase among young
people and this threatens to halt the downward trend in tobacco
smoking which has been evident in this country since the 1960s.
Tobacco-related illnesses and MRC research
15. MRC continues to support research into
smoking—for instance, to improve understanding about the
addictive nature of nicotine; the social, behavioural and economic
variables which influence smoking trends; the impact of "passive
smoking; and how best to develop and implement smoking cessation
strategies.
16. Research at the MRC Toxicology Unit
(Leicester) has identified a number of constituents of tobacco
smoke which have been shown to be carcinogenic, and which could
be useful biomarkers in quantifying the health risks of exposure
to passive smoking and maternal-fetal transmission.
17. There are a number of current research
projects investigating the underlying mechanisms of drug dependence,
including nicotine. For example, one project aims to determine
whether specific neurotransmitter receptors play a role in nicotine
addiction, using an animal model of nicotine dependence. The results
of this study should clarify mechanisms of nicotine dependence,
and might suggest possible compounds that would be effective in
smoking cessation therapy. Another project aims to distinguish
between receptor mechanisms through which nicotine produces dependence
and cognitive improvement. This should help the search for selective
compounds for aiding smoking cessation or reversing deficits in
certain dementias.
18. The MRC is funding other projects which
aim to further our understanding of the nature of tobacco dependence
and of the factors that determine its development, severity and
natural history. These include studies into the effects of nicotine
on mood, cognitive performance, and neuronal activity.
19. The MRC currently funds a number of
projects which are directly public health related, including long-term
epidemiological studies and trials to evaluate methods of cessation.
For example, the ongoing "Whitehall" study (a cohort
of civil servants) of Professor Marmot is investigating the aetiology
of heart disease and stroke, including the effects of smoking.
Other MRC funded projects include:
— the evaluation of peer-influenced
smoking intervention programme among 1,600 14-16 year-olds in
Mid-Glamorgan;
— a randomised controlled trial to
investigate the effectiveness of a low-cost self-help smoking
cessation package introduced early in routine antenatal care and
designed specifically for use with pregnant smokers; and
— a smoking cessation programme for
use in community pharmacies.
20. A great deal has been discovered about
the ill-health effects of tobacco smoking in the years since the
second world war. There is still a need to refine our understanding
of the risks from passive smoking, to understand better why people
smoke and how best to reduce or stop smoking. All the research
evidence to date fully supports the priority given to smoking
reduction in Our Healthier Nation and in the White Paper,
Tobacco Kills.
Medical Research Council
October 1999
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