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).
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.
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.