ANNEX
Memorandum to Martin Broughton from Dr
Chris Proctor
HOUSE OF COMMONS HEALTH COMMITTEE REQUEST
FOR SUPPLEMENTARY EVIDENCE
In response to your request, this memorandum
responds to Dr Benger's letter of January 14, requesting supplementary
evidence. I have taken each of the requests laid out in that letter
in turn. Several of the requests concern matters of significant
scientific complexity, and many research findings. For the purpose
of this note I have tried to keep the analysis as concise as possible.
1. Could you indicate the amounts your companies
spend on research annually, what proportion of turnover that represents;
and what proportion of that research is geared towards the health
risks of smoking?
The amount spent on research and development
by British American Tobacco prior to the merger with Rothmans
and as recorded in our last Annual Report and Accounts (1998),
was £45 million. Gross turnover for that same period was
£17,376 million giving a percentage of research budget compared
to gross turnover of 0.26 per cent. I would have thought that
this was not a reasonable way to express the company's investment
in R&D since the majority of this turnover goes to Government
in the form of excise duties and other sales taxes, and hence
is not available to the Company. Governments typically do not
specify how the excise revenues they obtain from tobacco sales
are allocated, but it could be assumed that some of this revenue
is invested in academic smoking and health research.
In terms of British American Tobacco's investment
in R&D, profit after tax may give a more realistic picture
of the Company's commitment to research given that this sum is
available for investment decisions. In 1998 profit after tax was
£461 million, making the R&D spend just under 10 per
cent of profit after tax. It should also be noted, however, that
1998 was an unusual year and included Brown and Williamson's costs
of settlement of the US Attorneys General actions. A further figure
that might give a better comparison is our 1998 adjusted profit
after tax, around £720 million, which would give a proportion
of spend on R&D of around 6 per cent.
It should also be noted that the pre-merger
Rothmans R&D budget was £25 million in 1998.
The proportion of research and development spend
relating to the health risks of smoking obviously depends on definitions.
As we stated in our initial memorandum to the Health Committee,
the internal research and development effort focuses on product
modification. In this regard, much of the R&D budget goes
to making assessments of the product, ensuring compliance with
regulatory standards, and looking to make product improvements,
both in terms of consumer acceptability and in terms of reducing
risks.
This work takes the results of externally published
research on smoking and health and seeks ways to apply those findings
to the product. To assess the scale of the academic research on
smoking and health a "medline" search using the term
smoking finds some 2,877 published articles in scientific journals
using the term smoking in the title of the paper in the year 1998
alone. There were some 4,516 scientific papers that mention smoking
in the text of the article.
It is also worth noting that while over the
years we have contributed significantly to the funding of academic
research on smoking and health, and to government supported programmes
such as the research managed by the Tobacco Products Research
Trust, our current ability to fund high quality independent research
is being limited by the views of bodies such as the Wellcome Trust
and the Cancer Research Campaign. These research funding bodies
have demanded that Universities do not take research grants from
tobacco companies, despite the fact that the grants are given
in the expectation that the interpretation and publication of
the research is at the sole discretion of the researcher.. These
issues were discussed in a series of articles, including an article
written by myself, in the British Medical Journal in 1998.
2. Could you indicate the outcome of legal
proceedings brought against SCOTH, and confirmation of whether
your company was a party to the action?
A British American Tobacco subsidiary company
was one of the companies that sought leave for judicial review
of the SCOTH report, which was published in March 1998. The initial
hearing granted leave to seek judicial review and the full hearing
late last year denied judicial review, in part, on the basis that
the SCOTH report was a consultative document and that the companies
had other means to address their concerns.
The process that was undertaken to produce the
SCOTH report was quite different from that undertaken by SCOTH's
predecessor, the Independent Scientific Committee on Smoking and
Health (ISCSH). The UK tobacco companies had been allowed to co-operate
with the ISCSH in the preparation of its four reports, which were
published in 1975, 1979, 1983 and 1988. In light of these reports
the UK tobacco manufacturers concluded a series of voluntary agreements
with the Government known as the Product Modification Programme
relating to the reduction of tar yields in cigarette brands. SCOTH,
established in 1994, took quite a different approach from its
predecessor by refusing to have any meaningful dialogue with the
tobacco companies outside of a very limited area. As a result
SCOTH included in its report statements, particularly on marketing,
which were both inaccurate and harmful to the tobacco companies
reputation and did not serve as a basis for further product modification
efforts. Throughout the period when the report was being written,
the companies made it clear that they wished to provide information
to the SCOTH Committee to assist their deliberations. The legal
challenge was a last resort to try and address the inaccuracies
stated in the report.
In the initial hearing the Judge commented that
it was questionable whether there was much scientific rigour in
the report which attacked the conduct of the companies.
It is also notable that the SCOTH Committee
concluded that environmental tobacco smoke (ETS) is a cause of
lung cancer based primarily on epidemiologic data, but did not
take into account the largest study on this subject—the
International Agency for Research on Cancer (IARC) multi-centre
European study. It was surprising that the Committee preferred
to rely heavily on an American study, by Elizabeth Fontham, rather
than a WHO-funded European study that included UK data. The IARC
study reported no overall statistically significant increase in
risk of lung cancer for those exposed to ETS at home, work, during
childhood, or in public settings. While many of the studies on
ETS and lung cancer have reported a very small (in epidemiologic
terms) increase in relative risk, the majority have not reported
overall statistically significant results indicating that if there
is a risk it is probably too small to measure, even with large
epidemiologic studies such as that carried out by IARC. In my
view, the epidemiology on ETS and lung cancer has not shown a
causal relationship.
The Committee should also be aware that, as
discussed in our memorandum, in a case in the US, Federal Judge
Osteen vacated sections in the US Environmental Protection Agency's
report on ETS and lung cancer on the basis of flawed scientific
analysis.
3. Could we have a reply to whether
your company believes that nicotine is addictive by reference
to each of these criteria:
(a) DSM-IV
DSM-IV refers to the American Psychiatric Association's
Diagnostic and Statistical Manual of Mental Disorders, Fourth
Edition. The question seems to misunderstand the purpose of DSM-IV
and the manner by which criteria are set out in DSM-IV. The manual
does not set out to define criteria for judging whether a particular
substance is addictive (or more accurately capable of producing
dependence). Rather, it provides standardised diagnostic criteria
to assist clinicians in determining whether a person has a particular
disorder.
The Manual covers a wide range of disorders,
and includes a section on substance-related disorders. This section
produces diagnostic criteria for 11 classes of substance—alcohol,
amphetamine, caffeine, cannabis, cocaine, hallucinogen-related,
inhalant-related, nicotine-related, opioid-related, phencyclidine-related,
sedative, hypnotic or anxiolytic use, polysubstance-related disorder
and other (or unknown) substance-related disorders. For each of
these substance classes the manual provides background information
and diagnostic criteria to assist a clinician in arriving at a
diagnosis of whether, for example, a patient is suffering from
alcohol intoxication or alcohol withdrawal.
It should be noted that the Manual typically
does not refer to the terms addiction or addictive. Rather it
discusses criteria to determine whether a person can be characterised
as dependent.
Within the sub-section on substance-related
disorders, DSM-IV discusses nicotine-related disorders, separating
nicotine use disorder from nicotine-induced disorder (which it
subdivides into nicotine withdrawal and nicotine-related disorder
not otherwise specified).
The criteria for clinical judgement on substance
dependence is given on page 181 of DSM-IV and states:
"Criteria for substance dependence
A maladaptive pattern of substance abuse, leading
to clinically significant impairment or distress, as manifested
by three (or more) of the following, occurring at any time in
the same 12-month period:
(1) tolerance, as defined by either of the
following:
(a) a need for markedly increased amounts
of the substance to achieve intoxication or the desired effect
(b) markedly diminished effect with continued
use of the same amount of that substance
(2) withdrawal, as manifested by either
of the following:
(a) the characteristic withdrawal syndrome
for the substance (refer to Criteria A and B of the Criteria sets
for Withdrawal from the specific substances)
(b) the same (or closely related) substance
is taken to relieve or avoid withdrawal symptoms
(3) the substance is often taken in larger
amounts or over a longer period than was intended
(4) there is a persistent desire or unsuccessful
efforts to cut down or control substance use
(5) a great deal of time is spent in activities
necessary to obtain the substance (eg visiting multiple doctors
or driving long distances), use of the substance (eg chain-smoking),
or recover from its effects
(6) important social, occupational, or recreational
activities are given up or reduced because of substance use
(7) the substance use is continued despite
knowledge of having a persistent or recurrent physical or psychological
problem that is likely to have been caused or exacerbated by the
substance (eg current cocaine use depite recognition of cocaine-induced
depression, or continued drinking despite recognition that an
ulcer was made worse by alcohol comsumption)"
For nicotine dependence, DSM-IV states that
"Some of the generic Dependence criteria do not apply to
nicotine, whereas others require further explanation." Nicotine
is the only substance in this section of DSM-IV where the manual
relies upon modifying the generic criteria.
I will take each of these generic criteria,
and refer to the nicotine-specific criteria, to see which might
be applied to some smokers.
For tolerance, it is generally not the case
that smokers need markedly increased amounts of nicotine to produce
a desired effect (note that DSM-IV determines that nicotine is
not intoxicating). Hence, generic criteria 1(a) would not be present
in most smokers. It should be noted that this was the definition
of tolerance used in the 1964 US Surgeon General's report (see
below).
Whether generic criterion 1(b), a markedly diminished
effect with continued use of the same amount of the substance,
would be applied to some smokers is questionable. DSM-IV suggests
that "Many individuals who smoke cigarettes consume more
than 20 cigarettes a day, an amount that would have produced symptoms
of toxicity when they first started smoking." Some people
trying to smoke for the first time, or some smokers who have not
smoked for a while, can experience a variety of responses such
as dizziness and nausea on taking a first cigarette. This typically
disappears after the second or third cigarette. In that this phenomenon
reappears after abstinence from smoking, it does not seem to be
a chronic tolerance effect.
For withdrawal, DSM-IV expands on criterion
2(a) by stating "a maladaptive behavioural change, with physical
and cognitive concomitants, that occurs when blood or tissue concentrations
of a substance decline in an individual who has maintained prolonged
heavy use of the substance". Criterion B for substance withdrawal
is described as "The substance-specific syndrome causes clinically
significant distress or impairment in social, occupational, or
other important areas of functioning". On quitting smoking,
some people exhibit a variety of mild symptoms. DSM-IV expands
specifically on diagnostic criteria for nicotine withdrawal, being:
"A. Daily use of nicotine for at least
several weeks.
B. Abrupt cessation of nicotine use, or
reduction in the amount of nicotine used, followed within 24 hours
by four (or more) of the following signs:
(1) dysphoric or depressed mood
(3) irritability, frustration or anger
(5) difficulty concentrating
(8) increased appetite or weight gain
C. The symptoms in B cause clinically significant
distress or impairment in social, occupational, or other important
areas of functioning.
D. The symptoms are not due to a general
medical condition and are not better accounted for by other mental
disorder."
Unlike the symptoms found after withdrawal from
alcohol or heroin, few smokers would exhibit clinically significant
distress or impairment in social, occupational or other important
areas of functioning, particularly if one considers "clinically
significant" as requiring the attention of a physician. Hence
whether you can describe some people as suffering nicotine withdrawal
under DSM-IV depends on the definition of clinically significant.
To this point, DSM-IV states "This criterion helps establish
the threshold for the diagnosis of a disorder in those situations
in which the symptomatic presentation by itself (particularly
in its milder forms) is not inherently pathological and may be
encountered in individuals for whom a diagnosis of "mental
disorder" would be inappropriate. Assessing whether this
criterion is met, especially in terms of role function, is an
inherently difficult clinical judgement. Reliance on information
from family members and other third parties (in addition to the
individual) regarding the individual's performance is often necessary."
It is worth comparing the diagnostic critera
for nicotine withdrawal with those for alcohol withdrawal. These
are given on page 198 of DSM-IV:
"Diagnostic Criteria for 291.81 Alcohol
Withdrawal:
A. Cessation of (or reduction in) alcohol
use that has been heavy and prolonged.
B. Two (or more) of the following, developing
within several hours to a few days after Criterion A:
(1) autonomic hyperactivity (eg, sweating
or pulse rate greater than 100);
(2) increased hand tremor;
(5) transient visual, tactile or auditory
hallucinations or illusions;
(6) psychomotoragitation;
C. The symptoms in Criterion B cause clincially
significant distress or impairment in social, occupational, or
other important areas of functioning."
Clearly some of the diagnostic criteria for
alcohol withdrawal would be clincially significant.
I agree that some smokers, on quitting, will
exhibit some or all of the symptoms listed in DSM-IV's diagnostic
criteria for nicotine withdrawal (symptoms that are generally
much milder than those given for alcohol withdrawal). However,
I disagree, since it would be rare that someone quitting would
seek specific clinical assistance to treat these symptoms, that
smoking meets the criteria on the basis of clincial significance.
It should be noted that DSM-IV states "Neither
tolerance nor withdrawal is necessary nor sufficient for a diagnosis
of Substance Dependence."
The third criterion, that the substance is often
taken in larger amounts or over a longer period than was intended,
could apply to some smokers. Similarly, the fourth criterion that
there is a persistent desire or unsuccessful efforts to cut down
could apply to some smokers.
The fifth criterion of a great deal of time
being spent in activities necessary to obtain the substance doesn't,
perhaps unsurprisingly (since availability of tobacco products
is commonplace and legal) fit tobacco. A small proportion of smokers
might be described as "chain-smokers", but I would assume
that most heavy smokers do not spend much more time in activities
necessary to obtain tobacco products than lighter smokers. DSM-IV
suggests that chain smokers fit this criterion in that they spend
a considerable amount of time using the product. By commonplace
definition, a "chain-smoker" would spend a lot of time
smoking, and even though "chain-smokers" will be doing
other things whilst they smoke, if this is the defintion for fulfilling
this criterion I can accept that some smokers will be characterised
as fulfilling this.
The sixth criterion of reducing important social,
occupational or recreational activities might apply to a very
limited number of smokers—for example, those who refuse
to take an aeroplane journey because they would not be allowed
to smoke. For the majority of smokers, I would have thought any
reasoanable assessment would judge that their smoking does not
reduce important social, occupational or recreational activities.
Some smokers may also fit the seventh criterion
of continued use despite knowledge of having physical or psychological
problems that could be caused or exacerbated by continuing to
smoke.
As we noted in our memorandum to the House of
Commons Health Committee, the American Psychiatric Association's
Diagnostic and Statistical Manual of Mental Disorders (DSM-IV)
is the standard text now used by most clinicians to diagnose,
communicate about, study and treat various mental disorders. In
its section on substance-related disorders it covers a variety
of substances including alcohol, nicotine and caffeine. It reports
that alcohol can be associated with abuse, intoxication, intoxication
delirium, withdrawal delirium, dementia, amenestic disorder, psychotic
disorders, mood disorders, anxiety disorders, sexual dysfunction
and sleep disorders. It does not characterise nicotine as being
associated with any of these diagnoses. It does determine that
nicotine dependence and withdrawal can develop with all forms
of tobacco use and with prescription medicines such as nicotine
gum and patch. It suggests that between 50 per cent and 80 per
cent of those who currently smoke have nicotine dependence and
that 50 per cent of those who quit on their own experience nicotine
withdrawal. DSM-IV also considers that around 14 per cent of the
US population could be defined as having alcohol dependence at
some time in their lives (approximately 12 million Americans).
On caffeine, DSM-IV suggests that caffeine intoxication can cause
a clinicial picture similar to nicotine withdrawal.
Given that under the DSM-IV generic criteria
for substance dependence only three (or more) of the seven criteria
need to be fulfilled in a patient to define them as having a substance-dependence,
and given that DSM-IV sets modified criteria for nicotine, I can
agree that there will be some smokers, under these criteria, that
will be classified as being dependent upon smoking.
(b) ICD 10
ICD 10 refers to the World Health Organisations
International Statistical Classification of Diseases and Related
Health Problems, Tenth Revision. This revision was published in
1992. The purpose of ICD is to set internationally consistent
codes for clinicians for a variety of different diseases and related
health problems so that, for example, international disease rates
can be assessed on a common basis.
Codes F10-F19 in ICD 10 refer to mental and
behavioural disorders due to psychoactive substance use. Code
F17 refers to mental and behavioural disorders due to use of tobacco.
DSM-IV, as noted above, refers to nicotine and included nicotine
replacement therapy, whereas ICD 10 refers to tobacco.
DSM-IV states "Those preparing ICD-10 and
DSM-IV have worked closely to coordinate their efforts, resulting
in much mutual influence. ICD-10 consists of an official coding
system and other related clinical and research documents and instruments.
The codes and terms provided in DSM-IV are fully compatible with
both ICD-9-CM and ICD-10."
Given the similarity, the above discussion on
DSM-IV applies to ICD 10. However, it is worth briefly describing
the sub-divisions that ICD 10 applies to substance-related health
problems.
The coding F17 (mental and behavioural disorders
due to the use of tobacco) is sub-divided by 9 further divisions
that are expressed with a fourth character (eg F17.2). Subdivision
.2 is dependence syndrome. This is defined, in ICD-10, Volume
1, as:
"A cluster of behavioural, cognitive, and
physiological phenomena that develop after repeated substance
use and that typically include a strong desire to take the drug,
difficulties in controlling use, persisting in its use despite
harmful consequences, a higher priority given to drug use than
to other activities and obligations, increased tolerance, and
sometimes a physical withdrawal state.
The dependence syndrome may be present for a
specific psychoactive substance (eg tobacco, alcohol), for a class
of substances (eg opioid drugs), or for a wider range of pharmacologically
different psychoactive substances."
A variance with DSM-IV appears in the list of
diagnostic guidelines in the ICD-10 Classification of Mental and
Behavioural Disorders, where guideline (d) states "evidence
of tolerance, such that increased doses of the psycho-active substance
are required in order to achieve effects originally produced by
lower doses (clear examples of this are found in alcohol- and
opiate-dependent individuals who may take daily doses sufficient
to inacapacitate or kill nontolerant users." This varies
with the dual criteria for tolerance set in DSM-IV, as noted above.
Under the broad diagnostic criteria presented
in ICD-10, I conclude that some smokers would be characterised
as having a dependence syndrome.
While not specifically requested in Dr. Benger's
letter, it is also worthwhile noting the derfinitions used in
the US Surgeon General's Reports—one from 1964 and one from
1988.
In 1964, the US Surgeon General's Report used
the recommendations of a World Health Organisation expert committee
to define drug addiction and drug habituation.
"Drug addiction is a state of periodic
or chronic intoxication produced by the repeated consumption of
a drug (natural or synthetic). Its characteristics include:
(1) An overpowering desire or need (compulsion)
to continue taking the drug and to obtain it by any means;
(2) A tendency to increase the dose;
(3) A psychic (psychological) and generally
a physical dependence on the effects of the drug;
(4) Detrimenal effect on the individual and
on society."
And "Drug habituation (habit) is a condition
resulting from the repeated consumption of a drug. Its characteristics
include:
(1) A desire (but not a compulsion) to continue
taking the drug for the sense of improved well-being which it
engenders;
(2) Little or no tendency to increase the
dose;
(3) Some degree of psychic dependence on
the effect of the drug, but the absence of physical dependence
and hence an abstinence syndrome;
(4) Detrimental effects, if any, primarily
on the individual."
The Report concluded that "In medical and
scientific terminology the practice should be labelled habituation
to distinguish it clearly from addiction, since the
biological effects of tobacco, like coffee and other caffeine-containing
beverages, betel morsel chewing and the like, are not comparable
to those produced by morphine, alcohol, barbiturates, and many
other potent addicting drugs."
In 1988, the US Surgeon General's Report defined
the criteria for drug dependence, which it said was equivalent
to drug addiction, as:
"Primary Criteria
— Highly controlled or compulsive use
— Drug-reinforced behaviour
Additional Criteria
— Addictive behaviour often involves:
— stereotypic patterns of use
— use despite harmful effects
— relapse following abstinence
— recurrent drug cravings
— Dependence-producing drugs often
produce:
The Report concluded that it was possible to
define dependence just on the primary criteria, hence needing
to take more and more of the substance to have the same effect
(tolerance) and being physically dependent were not necessary,
and that "cigarettes and other forms of tobacco are addicting."
I would be interested to know whether the committe,
or its advisors, believe that the US Surgeon General, in 1964,
was wrong not to call smoking an addiction under the definition
prevalent at that time.
This is obviously a complicated and emotional
area that is coloured by anecdotal and personal experience and
changes in scientific and commonplace definitions over time. The
Concise Oxford English Dictionary (Eighth Edition) defines an
addict as both "a person addicted to a habit, esp one dependent
on a (specified) drug (drug addict, heroin addict)"
and "an enthusiastic devotee of a sport or pastime (film
addict)."
The Chairman, in his opening remarks to the
last oral session, suggested that the evidence that tobacco company
representatives in the US had given had been shown to be "a
complete pack of lies". I assume that he may have been referring
to statements about nicotine not being addictive. As illustrated
above, the science and the definitions on these issues are complex,
and I as a scientist can see why someone might answer "no"
to a question of whether smoking was addictive when compelled
to give a "yes or no" answer, without being given the
opportunity to expand upon or clarify it.
In the context of the questions provided by
Dr Benger, my scientific advice is to respond that some smokers
could be classified as dependent under the criteria provided in
DSM-IV and ICD 10
4. Does smoking cause lung cancer—"cause"
meaning that smoking is an activity that results in there being
more lung cancer deaths than there would otherwise be—other
things being equal?
This definition of cause prompts consideration
of the epidemiologic data on smoking and lung cancer. It has long
been our view that there is considerable epidemiologic data to
conclude that smoking is an important risk factor for lung cancer.
Epidemiologic studies published since the 1950s have reported
a marked increase in incidence of lung cancer in smokers compared
to non-smokers. The same studies report that the incidence in
populations of smokers is greater for those groups that smoke
for a longer period, smoke more cigarettes per day and, in some
studies, smoke higher tar cigarettes. Studies also report that
the incidence of lung cancer is decreased in groups that quit
smoking compared to those that continue to smoke. On that basis
I believe it appropriate to say, under this definition, that smoking
is a cause of lung cancer.
5. Do you agree that smoking causes lung
cancer beyond all reasonable doubt?
The term "beyond reasonable doubt"
seems to be a legal phrase. It is not a term that is commonly
used in science and seems a strange term to use in these circumstances.
The answer to this question depends on whether
the question refers to populations or individuals. The epidemiology
on smoking and lung cancer is sufficiently strong to determine
that smoking is a cause of lung cancer in a population group.
This means that the incidence of lung cancer is likely to reduce
if either people smoke less or fewer people smoke. This is borne
out in UK lung cancer mortality statistics that currently show
a downward trend, particularly in males. Science has not identified
another factor, genetic or otherwise, that can explain the epidemiology.
So, from an epidemiologic viewpoint, I believe that the relationship
can be characterised as being "beyond reasonable doubt."
When it comes to individuals, there is much
still to understand. Scientists do not understand why the overwhelming
majority of lifetime heavy smokers do not contract lung cancer,
nor can scientists predict which lifetime smokers will contract
lung cancer and which will not. Science still has revealed relatively
little understanding of the biological mechanisms that could explain
the production of lung cancer in some individuals exposed long
term to tobacco smoke, and hence we have little certainty on which
product modifications might have a significant impact on the risks
associated with smoking.
So if the question refers to the determination
in an individual that smoking caused lung cancer beyond reasonable
doubt, my view is that existing science doesn't permit such a
judgement.
6. Does smoking cause heart and circulation
disease—"cause" meaning that smoking is an activity
that results in there being more heart and circulation disease
related deaths than there would otherwise be—other things
being equal?
The term "heart and circulation disease"
covers a wide range of diseases. The US Surgeon General's 1990
report discusses coronary heart disease (atherosclerosis, thrombosis,
spasm and arrhythmias), aortic aneurysm, peripheral arterial occusive
disease and cerebrovascular disease. Professor Sir Richard Peto
in "Mortality from Smoking in Developed Countries 1950-2000"
sub-characterises vascular disease as rheumatic heart disease
and fever, hypertensive disease, ischaemic heart disease, pulmonary
embolism and other venous, cerebrovascular disease, and other
vascular disease.
The epidemiology varies somewhat according to
the precise disease. However, in general, epidemiologic studies
have reported a higher incidence of some diseases of the heart
and circulation in groups of smokers compared to groups of non-smokers.
The same studies have also typically reported higher incidence
of some of these diseases in groups that smoke for longer periods
and more cigarettes per day than groups that smoke less, and groups
that quit smoking have a reduced incidence compared to groups
that continue to smoke. Smoking tends to be strongly associated
in epidemiologic terms, with peripheral artery disease, and less
strongly associated with many of the other heart and circulation
diseases. Most of these diseases are thought to have multi-factorial
risk profiles.
The relative risks for lifetime smoking and
certain diseases of the heart tend to be of the order of two to
three, considerably lower than the typical relative risks for
lifetime smoking and lung cancer and emphysema. For several of
the diseases of the heart and circulation, such as coronary heart
disease, the relative risks associated with the key risk factors,
such as smoking, hypertension, obesity, lack of exercise and hypercholesteremia
are of a similar order. Other risk factors of heart disease, such
as stress, diabetes, some personality characteristics and genetic
factors have also been identified. Some studies report that smokers,
on average, have a tendency to have more of the heart disease
risk factors, in addition to smoking, than non-smokers. This makes
it even more difficult to separate from the epidemiologic results
which portions of the relative risks may be due to smoking compared
to other risk factors. This has significant implications on attempts
to calculate smoking-attributable deaths. In Western countries,
heart disease tends to be the leading cause of death, and so even
a small lack of precision in the epidemiologic attribution of
a proportion of heart disease deaths to smoking (and given the
above the precision is likely to be poor) can lead to large inaccuracies
in the estimation of overall smoking-attributed mortality numbers.
Rarely do such numbers indicate the likely lack of precision or
the possible variance in estimate given the underlying assumptions
used to produce the estimates. Also, some studies have reported
that the identification of the key risk factors is not always
indicative of the prevalence of heart disease in a particular
population.
However, on the basis of the epidemiology, it
is reasonable to conclude that smoking is a cause of certain diseases
of the heart and circulation.
7. Do you agree that smoking causes
heart and circulation disease beyond all reasonable doubt?
The simple conclusion to this question is similar
to that for lung cancer, but the underlying epidemiologic data
is quite different, as explained above in my answer to question
6. Based on epidemiology, I believe that the relationship between
smoking and certain diseases of the heart and circulation can
be characterised as being beyond reasonable doubt.
When considering individuals, the scientific
situation is even more complicated than for lung cancer, given
that most of these diseases have a greater multi-factorial risk
profile than lung cancer. When it comes to individuals, there
is much still to understand. Scientists cannot predict which lifetime
smokers will contract diseases of the heart or circulation and
which will not. Science still has relatively little understanding
of the biological mechanisms that could explain the production
of diseases of the heart and circulation in some individuals exposed
long term to tobacco smoke, and hence we have little certainty
on which product modifications might have a significant impact
on the risks associated with smoking.
So if the question refers to the determination
in an individual that smoking caused heart and circulation diseases
beyond reasonable doubt, my view is that existing science doesn't
permit such a judgement.
8. Does smoking cause respiratory illnesses
such as emphysema—"cause" meaning that smoking
is an activity that results in there being more respiratory illness
related deaths that there would otherwise be—other things
being equal?
The epidemiology of smoking and emphysema reports
smoking to be an important risk factor for these diseases. Groups
of smokers tend to have much higher incidences of emphysema than
groups of non-smokers, and amongst groups of smokers the incidence
is much higher in groups that smoke for longer periods and smoke
more cigarettes per day than in groups of smokers that smoke less.
The incidence or severity of this disease also tends to be lower
in groups that quit compared to those that continue smoking.
On this basis, it is reasonable to conclude
that smoking is a cause of certain respiratory illnesses such
as emphysema.
9. Do you agree that smoking causes respiratory
illnesses beyond all reasonable doubt?
Again, the answer to this question depends on
whether the question refers to populations or individuals. The
epidemiology on smoking and certain respiratory illnesses such
as emphysema is sufficiently strong to determine that smoking
is a cause of these diseases in a population group. This means
that the incidence of certain respiratory illnesses is likely
to reduce if either people smoke less or fewer people smoke. Science
has not identified another factor, genetic or otherwise, that
can explain all of the epidemiology. So from an epidemiologic
viewpoint, I believe that the relationship is beyond reasonable
doubt.
When it comes to individuals, there is much
still to understand. Again, science has provided little understanding
of the biological mechanisms that explain the development of certain
respiratory illnesses such as emphysema in some individuals exposed
long term to tobacco smoke, and hence we have little certainty
on which product modifications might have a significant impact
on the risks associated with smoking.
So if the question refers to the determination
in an individual that smoking caused certain respiratory illnesses
beyond reasonable doubt, my view is that existing science doesn't
permit such a judgement.
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