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Stopping smoking has substantial immediate and long term health benefits for smokers of all ages. The excess risk of death from smoking falls soon after cessation and continues to do so
for at least 10-15 years.
Former smokers live longer than continuing smokers, no matter what age they stop smoking,
though the impact of quitting on mortality is greatest at younger ages. For smokers who stop before age 35, survival is about the same as that for non-smokers.
The rate and extent of reduction of risk varies between diseases—for lung cancer the risk falls over 10 years to about 30%-50% that of continuing smokers, but the risk remains raised even after 20 years of abstinence.
There is benefit from quitting at all ages, but stopping before age 30 removes 90% of the lifelong risk of lung cancer. The excess risk of oral and oesophageal cancer caused by smoking is halved within five years of cessation.
The risk of heart disease decreases much more quickly after quitting smoking. Within a year the excess mortality due to smoking is halved, and within 15 years the absolute risk is almost the same as in people who have never smoked.
In a meta-analysis by Wilson and colleagues in 2000, the odds ratio for death for smokers who stopped smoking after myocardial infarction was 0.54, a far higher protective effect than the
0.75-0.88 odds ratio for death achieved by the conventional standard treatments for myocardial infarction, including thrombolysis, aspirin, blockers, and statins. Smoking cessation also reduces the risk of death after a stroke and of death from pneumonia and influenza.
Smoking is associated with an accelerated rate of decline in lung function with age. Cessation results in a small increase in lung function and reverses the effect on subsequent rate of
decline, which reverts to that in non-smokers.
Thus, early cessation is especially important in susceptible individuals to prevent or delay the onset of chronic obstructive pulmonary disease.
In patients with this disease, mortality and symptoms are reduced in former smokers compared with continuing smokers. Recent evidence shows that the benefitsoccur even in older patients with severe chronic obstructive pulmonary disease.
At a population level, the importance of smoking cessation is paramount. Peto has estimated that current cigarette smoking will cause about 450 million deaths worldwide in the next 50 years. Reducing current smoking by 50% would prevent 20-30 million premature deaths in the first quarter of this century and about 150 million in the second quarter.
Preventing young people from starting smoking would have a more delayed but ultimately even greater impact on mortality.
Effective prevention of cigarette smoking and help for those wishing to quit can therefore yield enormous health benefits for populations and individuals. Promoting and supporting
smoking cessation should be an important health policy priority in all countries and for healthcare professionals in all clinical settings. However, this has not so far generally been reflected at a policy level or in the practice of individual healthcare professionals.
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Smoking and health 
