7.2 Health and other benefits of quitting
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A substantial body of research has established that quitting smoking has immediate as well as long-term health benefits for men and women of all ages, reducing risks for diseases caused by smoking and improving health in general.3, 16
The strongest evidence for this comes from a landmark 50-year follow up of 34,000 British male doctors first studied in 1951.17–19 Many participants quit as the evidence on smoking and health accumulated from the 1950s onwards, providing a natural experiment demonstrating the impact of number of years smoking on health and eventual mortality. The study showed just how hazardous smoking is and estimated that almost two-thirds of persistent smokers were killed by their smoking. Among those who quit, the greatest benefit was seen in those who quit earliest in life.19 Quitting at age 50 halved the risk of smoking-related death, but cessation by age 30 avoided almost all of the excess risk. Stopping at age 60, 50, 40 or 30 resulted in gains, respectively, of about three, six, nine, or 10 years of life expectancy.19
Changes in disease risk following cessation can be measured in different ways.
A common measure is relative risk (RR) where the likelihood of developing or dying of disease in a population of former smokers is compared to either current or never smokers. At a population level relative risk helps to understand the fraction of disease attributable to smoking. However this measure is influenced by the rates of disease in the reference population, which should be taken into account when examining the influence of cessation on disease risk.
Another measure is absolute risk, where the actual rates of disease in former smokers are compared to those of current or never smokers. Rates can be directly compared, or the excess rate of disease caused by smoking in smokers can be calculated as can the excess disease rate in former smokers. Another measure is cumulative risk of disease that enables the cumulative risk for those who quit at different ages to be compared to that of continuing smokers.
A more complete discussion of changes in risk following cessation can be found in a handbook published in 2007 by the International Agency for Research on Cancer.20[1] In general, the risk of disease is lower in former smokers than in otherwise similar current smokers. Smoking results in both acute and chronic changes to the body and progression towards disease. Cessation results in reversal of acute changes, slowing of disease progression and provides the potential for damage reversal.20
Many harmful effects of smoking are arrested or begin to decline as soon as a person stops smoking.3, 16 Many disease risks in former smokers continue to decrease with prolonged abstinence, compared to continued smoking. The risk for some health effects decreases more rapidly than others, and improvement may continue for years after quitting. Some disease risks return to that of never-smokers after a long period of abstinence, but others do not, even after 20 years of abstinence.20
The extent of damage to health and risk for smoking-related disease is related to how much the person has smoked and for how long.20 For some health effects, for example inflammation of the lung, the reversal process is not yet well understood.20
However, while some damage may be irreversible or less reversible, there are substantial benefits to be gained from quitting at any age, regardless of smoking history.3, 16 Benefits accrue to persons both with and without smoking-related disease.3
Upon cessation, the nicotine and carbon monoxide levels in the body decline rapidly within a few hours, and the main metabolites of nicotine are largely eliminated within a week.3, 20, 21 After a month, blood pressure returns to normal levels22 and small airway function improves, with further improvements after six months.23 After two months, improvements can be seen in blood viscosity, blood flow to the limbs and blood levels of high-density cholesterol.3, 24 Within a few months the cilia in the lungs and airways improve at sweeping mucus and debris from the lungs (as long as irreversible damage has not taken place).25 Symptoms of chronic bronchitis, such as chronic cough, mucus production and wheeze, decrease rapidly within a few months after stopping smoking.20 Rates of respiratory infections such as bronchitis and pneumonia also decrease, compared to continued smoking.3
Some of the specific benefits of cessation are:
- Lung cancer. Quitting at age 30 reduces the risk of lung cancer by several times compared to a lifetime smoker. Even quitting at 50 more than halves the risk over the next 25 years compared to continued smoking.26 The absolute annual risk of developing or dying from lung cancer does not decrease, but by stopping smoking the much greater increase in risk that would result from continuing to smoke is avoided.20
- Chronic obstructive pulmonary disease (COPD). In smokers without COPD, stopping smoking improves lung function by about 5% within a few months of cessation. The accelerated decline in lung function in smokers stops within five years of smoking cessation, returning to the far slower rates of decline that naturally occur with ageing.3, 20 Cessation slows the progression of COPD, but existing emphysematous damage to lung tissue caused by smoking is permanent.3 Symptoms of COPD will be less likely in the short and long term.3 In people diagnosed with COPD, stopping smoking reduces the rate of lung function decline, and decreases the risk of hospitalisation for COPD.20
- Heart disease. After one year the increased risk halves and after 15 years the rate is similar to that of a non-smoker.3 Quitting helps prevent atherosclerosis (the narrowing and hardening of the arteries due to build-up of plaque on the artery walls) advancing to heart disease and stroke.16, 20
- Stroke. There is a marked reduction in risk within two to five years of quitting. 20 After 15 years the risk of stroke is the same as a non-smoker.3
- Peripheral vascular disease. Quitting slows down the build-up of plaque on artery walls, so that the risk of the disease is substantially reduced. For those who already have the disease, amputations are less likely.3, 27
- Blindness. Cataract development and macular degeneration risks and progression are reduced after quitting.16
- Male erectile dysfunction is reduced when smokers quit.16
- Female fertility. Missed and painful periods are reduced after quitting, as is the risk of delayed conception and early menopause.28, 29 The increased risk of heart disease and stroke among women smokers who use the contraceptive pill is reduced.30
- Cancer. The risks of cancers of the mouth, throat, larynx, oesophagus, stomach, bladder, kidneys, pancreas and cervix are reduced after quitting compared to continued smoking, and continue to decrease over time.3, 20 The risks of pancreatic, oral and cervical cancers become similar to people who have never smoked, but the risks for the other cancers remain higher than never-smokers even after 15 to 20 years.3, 20
- Overall health and quality of life improve.3, 16
- Pregnancy. The US Surgeon General has stated that 'smoking is probably the most important modifiable cause of poor pregnancy outcome among women in the United States.' Women who stop smoking either before becoming pregnant or in the first three to four months of pregnancy, have infants with a similar birthweight to those infants born to women who have never smoked. 3 Women who stop smoking any time up to the 30th week of pregnancy have infants with higher birth weights than those who smoke throughout pregnancy. Reducing the number of cigarettes smoked, instead of quitting completely, does not appear to benefit the birth weight of the foetus.3 Low birth weight infants have a higher risk of illness, death and of developing diseases in childhood and adulthood.3, 16 Women who quit smoking before or during pregnancy reduce their risk of pregnancy complications, including preterm premature rupture of membranes and preterm delivery (birth at less than 37 weeks gestation).3, 28
As well as the health benefits of quitting, there are other obvious advantages. Financial savings for a pack-a-day smoker are about $3000 per year (2008 prices). Smokers who quit reduce their likelihood of financial stress and are likely to enhance their material wellbeing.31 As more public and private places become smokefree, ex-smokers avoid the inconvenience of having to go outside to smoke. Quitting avoids further smoking-related damage to skin, and slows the development of wrinkles.32 Life insurance is often cheaper,33 the risk of smoking-related fires is reduced34, 35 and people who quit have fewer sick days.16
Cutting down: are there health benefits?
Cutting down the number of cigarettes smoked each day is a common strategy used by smokers to reduce harm, to move towards quitting, or to save money.12, 36–38 However, research shows no noticeable improvement in health outcomes or lifespan among smokers who are able to cut down on a long-term basis.39–41 This is largely because smokers primarily seek a consistent level of nicotine. Those who cut down therefore tend to smoke the remaining cigarettes harder by taking more and larger puffs, and holding each puff longer. Thus they do not reduce their intake of toxins as much as the reduction in the number of cigarettes suggests.36, 42
[1] Footnote IARC (2007). IARC Handbooks of Cancer Prevention, Tobacco Control, Vol. 11: Reversal of Risk After Quitting Smoking. Lyon, France.
Copyright © 2012 The Cancer Council. All rights reserved.