Causes and control of chronic respiratory disease: looking beyond the smokescreen.

Editorial Causes and control of chronic respiratory disease: looking beyond the smokescreen Cigarette smoking is as strongly related to death from chronic bronchitis and emphysema as it is to mortality from lung cancer.' Symptoms of cough, phlegm, wheeze, and breathlessness are also much more common among individuals and populations who smoke, and are reduced when they quit the habit.2 A randomised controlled trial reported in this issue3 reinforces the simple public health message: when it comes to cigarettes, a change is not as good as a rest. Cigarette smoking in many developed countries is on the decline (though regrettably increasing in popularity elsewhere). In Britain, current smokers have been in the minority among adults ofboth sexes since the late 1970s and, if current trends continue, less than one quarter of the population will be active smokers by the year 2000. How will the problem of chronic respiratory disease change as smoking declines and other causes which have for so long been obscured by the effects of smoking increasingly require investigation and control? It is likely that, even if smoking were entirely eliminated, a substantial burden of chronic respiratory morbidity would remain. Respiratory symptoms and illnesses are not uncommon in lifelong non-smokers, as illustrated by data from the British 1946 cohort reported in this issue.4 Reduced levels of ventilatory function would also remain of concern as a risk factor for (even if not a cause of) all mortality.5 The decline in smoking among British men in recent decades has been accompanied by a fall in the prevalence of phlegm and breathlessness, but not of wheeze, despite the fact that wheeze is more commonly reported by cigarette smokers.2 This suggests that morbidity related to asthma may become of relatively greater importance as smoking declines. The relationships of allergy and asthma to mucus hypersecretion (causing cough and phlegm) and to irreversible airflow obstruction (the main cause of disabling breathlessness and premature death from respiratory disease) are complex. A large volume of related clinical and epidemiological research has not so far identified the direction of cause and effect.6 Although these syndromes often coexist, particularly in persons who smoke, it is likely that each has distinct causes and mechanisms, which may be clarified by aetiological research among non-smokers. The review of findings from the 1946 cohort4 is a timely reminder that factors other than smoking play a role in the causation of chronic respiratory disease …