PREVENTION AND HEALTH: SMOKING DISEASES
Smoking diseases are diseases caused directly or indirectly by smoking tobacco. The best known is lung cancer but this is only the tip of the iceberg, as we shall see.
Smoking is the single greatest cause of death in the UK, and the World Health Organization has said that the control of smoking would do more good than any other single action in preventive medicine. At least 100,000 deaths are attributable to smoking in Britain each year with an average loss of about ten years of life. It accounts for 90 per cent of deaths from lung cancer; 75 per cent of deaths from chronic bronchitis; and 25 per cent of deaths from coronary heart disease in men under 65. The risk of coronary heart disease attributable to smoking is greater in younger men so that a man under 45 who smokes twenty-five or more a day may have a fifteen times greater risk of dying from a heart attack than if he were a non-smoker. Here are some chilling facts:
• Early studies suggested that relative mortality risks among female smokers were less than those of male smokers, but it is now clear that these studies were comparing the death rates of a generation of lifelong male smokers with a generation of women who had taken up smoking much later in life. The smoking characteristics of the two sexes are now becoming more and more alike, and the rates of smoking-related diseases are drawing closer together.
• Women who take the contraceptive pill and who also smoke cigarettes are more likely to have a coronary attack, stroke, and blood clots in the leg veins which may shift to the lung (pulmonary embolus), than are non-smokers who are on the Pill. One study has shown that for women aged 25-34 on the Pill the relative risk of death from circulatory disease was 1.6 for non-smoking Pill takers but 3.4 for smokers; women aged 35-44 the risks were 3.3 and 4.2 respectively, and for women over 45, 4.6 and 7.4. There is also a considerable increased risk for women on the Pill who smoke and who have one or more known risk factors for coronary heart disease.
• The natural menopause occurs on average 2-3 years earlier in smokers.
• Fetal growth and birth weight. Babies born to women who smoke are on average 200 g lighter than babies born to comparable non-smoking mothers. The relationship between maternal smoking and low birth weight is independent of all other risk factors which influence birth weight including maternal size, race, socio-economic status and the sex of the child. Furthermore, the more cigarettes a woman smokes during pregnancy, the greater the probable reduction in birth weight. However, if a woman stops smoking before the twentieth week of pregnancy, her risk of having a low-weight baby will be similar to that of a non-smoker.
• Children whose mothers smoke ten or more cigarettes after the fourth month of pregnancy tend to show poor progress at school, at least up to the age of 16. In both reading and mathematics tests they do less well than other children. This effect is found after allowing for other factors affecting educational level.
• Spontaneous abortion. Tobacco use during pregnancy causes a two-fold increase in the risk of spontaneous abortion (miscarriage).
• Complications of pregnancy. On average, smokers have more complications of pregnancy and labour, which can include bleeding during pregnancy, premature detachment of the placenta and premature rupture of the membranes.
• Perinatal mortality (defined as still-birth or death of an infant within the first week of life) increases in direct relation to the number of cigarettes smoked during pregnancy. In one large study, the perinatal mortality risk increased by 20 per cent for the infants of smokers of less than twenty cigarettes per day and by 35 per cent for smokers of twenty or more a day, compared with that of non-smokers.
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