Respiratory effects of lowering tar and nicotine levels of cigarettes smoked by young male middle tar smokers. I. Design of a randomised controlled trial.

STUDY OBJECTIVE: The aim was to investigate the effect on respiratory health of male middle tar smokers changing the tar and nicotine levels of the cigarettes they smoke for a six month period. DESIGN: This was a randomised controlled trial. Middle tar smokers were randomly allocated to smoke one of three different types of cigarette (low tar, middle nicotine; middle tar, middle nicotine; and low tar, low nicotine) in place of their usual cigarette for a six month period. Main outcome measures were assessment of respiratory health by documenting respiratory symptoms and peak expiratory flow rates, and of nicotine inhalation by measuring the urinary excretion of nicotine metabolites. SETTING: 21 local authority districts of England. SUBJECTS: Participants were male middle tar smokers aged 18-44 years. MAIN RESULTS: Postal questionnaires were sent to 265,016 individuals selected from the electoral registers of 21 local authority districts of England; 64% of questionnaires were returned revealing 7736 men aged 18-44 years who smoked only middle tar cigarettes. Of these, 7029 (90%) were sent a health warning and 707 (10%) were not; the latter acted as a control group to assess the effect of the health warning. Of the 7029 men who had received a health warning and were visited at the recruitment stage, 2666 agreed and were eligible to participate in the trial although only 1541 (58% of those who agreed and were eligible) actually started smoking the study cigarettes; 643 men (24% of those willing to participate at the beginning of the trial and 42% of those who actually started smoking the study cigarettes) completed the trial smoking the study cigarettes. Of these, 213 were in the low tar middle nicotine group, 220 were in the middle tar middle nicotine group, and 210 were in the low tar low nicotine group. CONCLUSIONS: This study shows the feasibility of identifying and recruiting sufficient numbers of male middle tar smokers, with adequate numbers completing the trial, to detect any changes in respiratory health over a six month period.

Respiratory effects of lowering tar and nicotine levels of cigarettes smoked by young male middle tar smokers. II. Results of a randomised controlled trial.

STUDY OBJECTIVE: The aim was to investigate the effect on respiratory health of male middle tar smokers changing the tar and nicotine levels of the cigarettes they smoke for a six month period. DESIGN: This was a randomised controlled trial. Middle tar smokers were randomly allocated to smoke one of three different types of cigarette (low tar, middle nicotine; middle tar, middle nicotine; and low tar, low nicotine) in place of their usual cigarette for a six month period. Main outcome measures were assessment of respiratory health by documenting respiratory symptoms and peak expiratory flow rates, and of nicotine inhalation by measuring the urinary excretion of nicotine metabolites. SETTING: 21 local authority districts of England. SUBJECTS: Participants were male middle tar smokers aged 18-44 years. MAIN RESULTS: Changes in the measures of respiratory health showed little difference over the trial period between the three cigarette groups. Analyses of the urinary nicotine metabolites showed that smokers allocated to each of the three study cigarettes adjusted their smoking so that throughout the trial their nicotine inhalation differed little from their pretrial intakes when they were smoking their own cigarettes. As a result of the altered patterns of smoking to compensate for the reduced nicotine yields of the three study cigarettes, the tar intake of those allocated to smoke the middle tar, middle nicotine cigarettes remained essentially unchanged, while those allocated to smoke the low tar, low nicotine and low tar, middle nicotine cigarettes had calculated reductions in tar intakes of about 14% and 18%, respectively. CONCLUSIONS: Due to the phenomenon of compensation, tar intake can only be reduced substantially by using a cigarette with a markedly lower tar/nicotine ratio. Nevertheless reductions of up to about 18% in tar intake failed to result in any detectable effect on respiratory symptoms or peak expiratory flow rates over a six month period.

Hospital admission rates and the prevalence of asthma symptoms in 20 local authority districts.

Representative samples of 20-44 year old men living in 20 local authority districts in England were surveyed in 1986 by postal questionnaire and asked about symptoms associated with asthma and treatment for asthma. Regional health authorities provided information on all hospital discharges of men of the same age living in the same districts. Specific information was also provided on discharges where the primary cause of admission was for asthma. Admission rates for asthma were related to the prevalence of night time breathlessness and independently to the all cause admission rate for men of the same age. Admission rates were not significantly related to prescription rates of either corticosteroids or beta 2 agonists for symptomatic men. This lack of association is hard to interpret without further information on variation in the severity of disease. These data show that admission rates for asthma are not dictated solely by health service characteristics, such as availability of beds or the "style" of the physician, but also reflect need. More research is required on how best to reduce the local prevalence and severity of asthma.

Repeatability of a questionnaire to assess respiratory symptoms in smokers.

To evaluate the repeatability of a questionnaire designed to assess change in respiratory symptoms 90 smokers were interviewed on two occasions. The questionnaire included questions from the Medical Research Council questionnaire on respiratory symptoms, questions on acute chest illness and cough and phlegm production in the preceding two weeks, a modification of Field's card system for estimating frequency of cough, and an objective assessment of the presence of phlegm--the loose cough sign. The study was carried out in two parts. During the first part 30 male smokers were interviewed by one observer and then re-interviewed 1 to 2 hours later by a different observer. During the second part 60 subjects were interviewed and then after a period of 1 to 10 days re-interviewed by the same observer. The results showed that the within-subject variation representing the measurement error for Field's card system was 15.1% of the between-subject variation and was adequately Normal to justify the use of standard analytical techniques. Similar results were obtained from questions on cough and phlegm scored between 1 and 5, although the variation in this case was rather less Normal. In general, the between-observer, within-observer, and within-subject repeatability were satisfactory for all parts of the questionnaire with the exception of the loose cough sign which had a relatively low prevalence. There was no evidence of an observer order effect and there were no important systematic differences due to lapses in time or different observers.The findings indicate that the techniques such as the cough scoring system may be used to permit studies of respiratory symptoms via questionnaire methods to be much smaller than those required to detect equivalent differences in prevalences.