Download Natural history of smoking WAC 11

Rene Maximiliano Gomez, MD
Head, Allergy & Asthma Unit
Hospital San Bernardo, Salta - Argentina
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The causes of death in order of incidence are
cardiovascular diseases (43%), all forms of
tobacco-caused cancer (36%), respiratory
diseases (20%), and all other smoking-caused
deaths (1%).
The three primary causes of mortality are similar
for men and women: heart disease, cancer, and
stroke
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“Addiction" has been more broadly used to refer
to compulsive use of psychoactive drugs in which
tolerance and physiological dependence may
also be present.
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The term physiological dependence will be used
to refer to the physiological adaptation
manifested by the emergence of withdrawal
symptoms after cessation of use.
The patho-physiological consequences of
tobacco smoke exposure include tissue
destruction contributing to lung disease, cellular
changes contributing to cancer, and the cellular
and molecular reinforcing effects leading to
dependence.
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Most smokers identify smoking as harmful and
express a desire to reduce or stop smoking, and
nearly 20 million of them (more than one-third of
all smokers) make a serious attempt to quit each
year.
Unfortunately, less than 7% of these smokers
attempting to quit (or less than 3% of all
smokers) achieve 1-year abstinence each year
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Approximately 50% of the survivors of myocardial
infarctions, lung removal, and tracheostomy resume
smoking.
This illustrates two important points. First, powerful
motivational incentives can lead to cessation; no
widely used formal treatment reliably establishes
50% rates of long-term abstinence. Second, this
powerful motivational contingency (i.e., threat of
death) is inadequate for 50% of cigarette smokers;
they may also require medications, behavior
modification procedures, or both.
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Nicotine dependence is a "progressive,"
"chronic," "relapsing" disorder.
Mean age of cigarette smoking onset is 13-14
years.
The level of nicotine dependence in adults is
inversely related to the age of smoking initiation
when measured by diagnostic criteria of the
American Psychiatric Association
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Continued smoke intake is accompanied by the
development of tolerance and physiological
dependence. After smoking a few cigarettes,
estimates of people who progress to dependence
ranges from roughly 33% to 50% (USA – UK).
Surveys differ in their criteria for initial smoking
and dependent smoking.
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Nicotine tolerance appears to be substantially
acquired during youth as smokers progress from
a few to many cigarettes to obtain same effects
There are several physiological mechanisms of
nicotine
tolerance,
including
decreased
responsiveness to the drug at the site of drug
action and increased nicotine receptor number
and some degree of increased metabolism
The rapid pharmacodynamic development of
tolerance may contribute to the disappointment
with nicotine replacement systems expressed by
many patients.
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Abstinence is usually short-lived; most
individuals resume smoking within 3 days.
Providing minimal assistance prolongs the
remission by at least a few more days, and
providing nicotine replacement can extend the
mean remission duration by 6 months or more.
One year later, nearly one-third of those
surveyed had relapsed, a testament to the
persistence of the dependence
A Gallup Survey of cigarette smoking and markers of
dependence indicated that
 40% of teenage smokers begin smoking within 1 hr
of awakening (sign of dependence);
 50% of teenage smokers had tried to quit but
relapsed;
 70% would not start smoking if they could "do it
again"; and
 38% of teenage smokers would be interested in
smoking cessation programs targeted to their needs
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38% were smoking at the time of the survey and
reported that they needed tobacco or felt dependent
at the time the survey was conducted, and
approximately 80% of people who smoked at least a
pack per day felt that they were dependent.
By contrast, among people who had consumed
alcoholic beverages in the past year, 30% had
consumed at least once in the past week; and among
those who had binged (five or more drinks in a row)
in the past 30 days, 17% reported they felt they
needed to drink or were dependent.
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It has been widely assumed that moderate daily use of
tobacco over an extended period of time is a prerequisite
for nicotine dependence. The Development and
Assessment of Nicotine Dependence in Youth (DANDY)
study contradicts this view, with results indicating that
the first symptoms of nicotine dependence can appear
within a matter of days or weeks of the onset of
intermittent tobacco use. These first symptoms were
strongly predictive of long term tobacco use, indicating
that the loss of autonomy over tobacco can occur very
rapidly with minimal exposure to nicotine.
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Chronic use is highly resistant
to modification. For example,
efforts to reduce intake by
smoking fewer cigarettes or
cigarettes with lower nicotine
delivery ratings are usually
partially
or
completely
thwarted by compensatory
changes in how the cigarettes
are smoked
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Accelerated decline in lung
function, more severe symptoms,
impairment in quality of life and
diminished therapeutic response to
steroids.
Can influence innate immunity
diminishing innate production of
antigen presenting cells cytokines,
as well as an impaired response to
toll-like receptor ligands.
Associated with current symptoms
of asthma and rhinitis, and risk
factor for developing new asthma
in patients with rhinitis.
Inducer of nasal obstruction and
decreased muco-ciliary clearance in
nonallergic rhinitis.