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COPD, chronic obstructive pulmonary disease; IHD, ischaemic heart disease.

COPD, chronic obstructive pulmonary disease; IHD, ischaemic heart disease.

has been derived from a series of very different studies over many years. Although none of these have used the randomized controlled trial design that provides the 'gold standard' for evidence in most Cochrane reviews, it is widely accepted that cigarette smoking is the single most important risk factor for the development of COPD, even though a precise model of the mechanism has yet to be constructed. It is worth reviewing the strength of the evidence.

As late as 1948, there were experts prepared to argue that smoking was not harmful, but by 1950 the link to lung cancer seemed probable. Richard Doll and colleagues decided to commence a prospective longitudinal study to find out what other diseases might or might not be smoking-related. In 1951, all doctors in Britain were asked about their smoking habits, and 40 000 replied. These doctors were followed up for 40 years, with interim reports at 10 and 20 years that confirmed the link to cancer and showed that other conditions were also linked to smoking. The 40-year report [1] concentrated on the 34439 males in the study, and at this time it was possible to establish the vital status of 99.7% of the 1951 cohort. A cause of death was obtained for 99% of the deaths, and of those who were alive, 94% completed a further questionnaire. Longitudinal studies are usually marred by a significant loss to follow-up, and the completeness of this study is remarkable. Although it was not a randomized, controlled trial, it is probably one of the most complete and devastatingly strong observational studies ever mounted.

Positive associations with smoking were confirmed for death from cancers of the mouth, oesophagus, pharynx, larynx, lung, pancreas and bladder. Details of mortality for COPD, lung cancer and ischaemic heart disease (IHD) are outlined in Table 1.1. Cigarette smoking increased the risk of death from COPD, lung cancer and from ischaemic heart disease. In each case, those who had ceased smoking had values that were intermediate between those of non-smokers and continuing smokers. Because ischaemic heart disease is so much more common, the total effects of cigarette smoking on the heart were similar to those on the lung. Thus, when expressed in terms of the population

Fig. 1.1 Relative risks of current smoking—the risk in non-smokers for each condition has been set at 1, and values displayed for different intensities of smoking.

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The Smoker's Sanctuary

The Smoker's Sanctuary

Save Your Lungs And Never Have To Spend A Single Cent Of Ciggies Ever Again. According to a recent report from the U.S. government. Centers for Disease Control and Prevention, more than twenty percent of male and female adults in the U.S. smoke cigarettes, while more than eighty percent of them light up a cigarette daily.

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