By Dr Chesterfield-Evans
Probably the most significant paper at the 9th World Conference on Smoking and Health, held in Paris October 10-14, was the presentation by Richard Peto of the latest results of the study of smoking and death rates in British doctors which was started in 1951.
When Richard Doll found the link between smoking and lung cancer in 1950, he wrote to all doctors registered in the UK and asked them to record their smoking habits. Forty thousand replied, and he set up a study to measure their survival. Ten thousand died in the first 20 years of the study, and 20,000 have died in the second 20 years.
The death rate of smokers in the age group 45-64 is about three times as high in smokers as lifetime non-smokers, and this is in diseases caused by smoking. The risk of dying is higher than was formerly thought, and it is now estimated that approximately half of regular smokers will be killed by their habit.
Diseases that were commoner in smokers were: cancers of the lung (15 times more common than in non-smokers), oesophagus, stomach, urinary bladder and pancreas. Lung problems of chronic bronchitis, emphysema, asthma and pneumonia were commoner, as were the circulatory problems of pulmonary heart disease, aortic aneurism, ischaemic heart diseases and cerebrovascular disease (strokes). The difference in deaths from ischaemic heart disease between smokers and non-smokers is 1.76:1 after standardisation for alcohol consumption. (Interestingly, a few alcohol drinks per day seem to prolong life.)
It is pointed out that the death rate from heart attacks and strokes in smokers is double that of non-smokers, but because these deaths are earlier or follow periods of long-term disability from middle age, their significance is even greater. Peptic ulcer is three times and cirrhosis of the liver is five times commoner in smokers, though this last may be because smokers tend to drink more heavily.
Parkinson's disease is less common in smokers, but Doll and Peto speculated whether this may not have been a health effect, but merely that the tremor of the disease meant that its sufferers have difficulty smoking, hence become "former smokers".
As the smoking and non-smoking groups reached later middle age, the differences between them increased. There were also deaths due to fires caused by smoking in bed. Pipe and cigar smokers are intermediate between cigarette smokers and non-smokers.
The big message is that half of lifetime smokers will be killed by tobacco and half of these (that is, a quarter of all smokers) will die in middle age (35-69), losing an average of 20-25 years of life compared to a non-smoker. Just over half of deaths in middle age are caused by tobacco. More than twice as many deaths are caused by cardiovascular disease as cancers.
The effect of quitting even in middle age is to reduce the rate, so "it's never too late to quit".
[Reprinted from Non-Smokers' Update, Box 6, 4 Goulbourn St, Sydney 2000.]