Public Health And Smoking
Respiratory disease accounts for approximately 20% of all deaths in the UK.
Acute infections (30.5%), progressive non-malignant disease (30.6%) and lung
cancer (29.6%) are the main causes (Fig. 22a). Annually respiratory illness is
responsible for approximately 850 000 hospital admissions, 13% of emergency
admissions and 10% of hospital bed days. Chest disease varies geographically in
relation to socioeconomic conditions with acute infectious illness, HIV-related
disease and post-tuberculous bronchiectasis more frequent in developing
countries and chronic obstructive pulmonary disease (COPD), cystic fibrosi and
restrictive chest wall defects (e.g. obesity hypoventilation and muscular
dystrophy) more common in the USA and Europe.
Factors associated with respiratory
disease
1 Smoking-related disease (SRD) is recognized as the single greatest cause of
preventable illness and mortality. It accounts for 5 million deaths/year
worldwide and 114 000 deaths/year in the UK due to a wide variety of illness
including lung or non-respiratory cancers (e.g. renal and bladder), COPD,
ischaemic heart disease (IHD), peripheral vascular disease, stroke, pneumonia,
interstitial lung disease, venous thromboembolism, diabetes, inflammator bowel
and peptic ulcer disease. In pregnancy smoking impedes fetal growth and
increases the risk of obstructive airways disease in the child. Inhaled
'second-hand' or passive smoking increases lung cancer risk and is thought to
cause approximately 12 000 deaths/year in the UK of which approximately 500 are
due to workplace smoke exposure.
Tobacco smoke contains many
potentially toxic gases including carbon monoxide, detected as
carboxyhaemoglobin in the blood, and polycyclic aromatic hydrocarbons which cause
gene mutations frequently found in primary lung cancers. Cigarette smoke
accelerates normal age-related loss of lung function (Fig. 22b) and is the
principal cause of COPD (Chapter 26). It also impairs epithelial ciliary
function and mucociliary transport (Chapter 18), and stimulates goblet cell
hyperplasia which contribute to the characteristic morning cough and excessive
sputum expectoration experienced by regular smokers.
Worldwide, 20 billion cigarettes are
smoked by 2 billion individuals. Oral and other smoked tobacco products are
also popular. However, recent legislation, smoking bans, changes in social
attitude and taxa- tion have significantl reduced the numbers of people
smoking. Consequently, in many developed countries, the incidence of SRD is no
longer rising (e.g. UK), or has fallen (e.g. USA). Sadly, increased smoking in
developing societies, partly due to advertising, means that the current low
levels of SRD in these countries are likely to rise.
COPD will rank third in worldwide burden of disease by
2020. In the UK it affects approximately 14% of people over 35 years old (7-18%
of men and 3-7% of women). However, COPD is of- ten unrecognized, despite
relatively severe disease, and only 0.9 of 3 million probable UK cases have
been diagnosed. In the USA approximately 2 million people have emphysema and
half have reduced exercise tolerance. COPD exacerbations are the commonest
cause of emergency hospital admission (Fig. 22c), with an average hospital stay
of 5 days, result in 24 million lost working days annu- ally, account for
approximately 13% of adult disability and cost the economy approximately £2
billion/year in the UK.
Lung cancer (Chapter 40) is the commonest cause of cancer
death in men and women in the USA and Europe. Smoking increases the risk by
30-fold compared to non-smokers (<1% lifetime risk) and is dependent
on dose (i.e. number of cigarettes/day, depth of inhala- tion, years smoked),
age of onset of smoking, ethnicity (e.g. greater in blacks), geographical area
(e.g. Scotland and Kentucky) and pattern of smoking (i.e. quit periods reduce
future risk). Age-standardized incidence rates are approximately 65/105 for
males and approxi- mately 39/105 for females in the UK and USA. In Europe,
Hungary has the highest (>100/105) and Sweden the lowest (<25/105)
incidence. Central Africa and south central Asia have the lowest lung cancer
rates. In the UK, approximately 35 000 lung cancer deaths occur annually, and
after prostate cancer, it is the second commonest cancer in men, causing approximately
22 000 new cases/year and third commonest in women after breast and bowel
cancer, causing approximately 16 000 new cases/year.
Environmental and social factors. Air pollution ( passive smoking), living
conditions and poor sanitation increase susceptibility to acute infective
diseases, asthma and hypersensitivity pneumonitis. Clean air initiatives,
environmental legislation and socioeconomic pro- grammes including better
nutrition, access to clean water and education programmes (e.g. breast feeding
and safe sex) have been beneficial.
Asthma (Chapter 24) is the commonest respiratory disease
in the UK, affecting 10-15% of the population, but there is considerable
variation in worldwide prevalence, with highest levels in English-speaking
countries. The cause of the recent increase in asthma in- cidence is unknown.
Potential factors include dietary changes, improved standards of living,
aeroallergens, environmental pollution, childhood infection and immunizations.
· Working conditions. Protection against inhalation of mineral and
organic dusts, chemicals and drugs have reduced susceptibility to occupa-
tional lung disease (e.g. coal workers' pneumoconiosis), work-related asthma
and hypersensitivity pneumonitis (see Chapter 33).
Smoking cessation
In the UK, 24% of men and 23% of women
smoke. However, smoking prevalence is highest in young adults (32% in 20-24
years old), manual occupations, socioeconomically deprived people and men of
South Asian descent. Chinese and Indian women are least likely to smoke. Most
smokers (>80%) start as teenagers and by 15 years of age 24% of girls
and 16% of boys are regular smokers (average 42 cigarettes/week), despite it
being illegal to sell tobacco to children. Factors associated with childhood
smoking include parental smokers, one-parent families, poor academic progress
and tobacco advertising.
Over two-thirds of smokers want to
stop smoking. A third try every year. Successful smoking cessation reduces the
risk of lung cancer by approximately 90%, but the risk is always higher than in
lifelong non- smokers. The main barrier to smoking cessation is nicotine, which
is highly addictive. Inhaled nicotine reaches the brain within 7-10 sec- onds
of smoking a cigarette. It acts on brain nicotinic acetylcholine receptors
(nAchR), which release neurotransmitters including noradrenaline (arousal,
appetite reduction), serotonin (mood regulation), vasopressin (memory
improvement), β-endorphin (anxiety reduction), and most importantly
dopamine from the mesolimbic dopamine system or 'brain reward pathway' which
elicits pleasure and is associated with the development of addictive behaviour.
Smoking cessation results in physical and psychological withdrawal from the
effects of these neu- rotransmitters and is associated with increased appetite
and an average weight gain of 2 kg.
Management
Success of smoking cessation depends
on both behavioural and phar- macological therapies. It is vital that the
smoker is motivated to stop at the outset. To achieve sustained abstinence, the
initial short-term nicotine craving is relieved with pharmacotherapy for 6-12
weeks, followed by ongoing intensive behaviour support.
a Behavioural Strategies
All health professionals should
address smoking cessation at every opportunity. Simple clinician counselling
stimulates a quit attempt in 40% of smokers. Counselling includes the 5As:
Assess risk of continued smoking and inform the patient Advise how to
stop smoking and what help is available Assist with behavioural support
or replacement therapy Arrange follow-up
Although brief counselling alone is
only associated with quit rates of 1-3%, more intensive individual and
group-counselling sessions with a 'quit date' can achieve abstinence in 20% at
1-year follow-up. Telephone follow-up, web-based support and multiple
interviews all improve cessation rates. Evidence for benefi with hypnosis or
acupuncture is weak, but these are helpful after previous failed attempts. b
Pharmacotherapy
Nicotine replacement therapy (NRT) ameliorates nicotine withdrawal symptoms including
insomnia, irritability, anger, anxiety, poor concentration and increased
appetite. It is safe, even in patients with known cardiovascular diseases.
Intensive behavioural support, combined with NRT, can achieve 1-year abstinence
rates of 25% (compared to 10% with usual care). Nicotine is available as
transdermal patches, gum, sublingual tablets, nasal sprays and inhalers; all
are equally effective. A patch raises baseline blood nicotine levels, but
combined use of a second NRT (e.g. gums, lozenges, inhalers) to provide 'bursts
of nicotine' helps overcome breakthrough urges, improving long-term success.
Antidepressants correct the low dopamine levels due to nicotine
dependence. Smokers who are not depressed may also benefi from this approach. Bupropion
(Zyban), a dopamine uptake inhibitor, doubles normal quit rates.
Combination with nicotine patches is not always beneficial Bupropion is
contraindicated in epilepsy and pregnancy. Nortryptiline, a tricyclic
antidepressant, is an effective second-line agent.
Varenicline, a partial agonist of nAchR, reduces withdrawal
cravings and decreases the reward effects of smoking. Twelve-week quit rates
comparing vareniciline, bupropion and placebo were 45, 30 and 18%,
respectively, and at 12 months were 23, 16, and 9%, respectively. Varenicline
is particularly effective when combined with e behavioural therapy.
