A double-blind randomized controlled trial of the effect of a low- versus a middle-tar cigarette on respiratory symptoms--a feasibility study.

A feasibility study of a double-blind, randomized controlled trial of the effect of a low-versus a middle-tar cigarette on respiratory symptoms is described. A smoking questionnaire was sent to 19,366 households. Returned questionnaires (64%) yielded 604 middle-tar cigarette smokers aged 20-44 years; 342 replied to a health warning stating that they did not want to or had failed to stop smoking and of these 183 volunteered for the trial. Thus about every 100 households originally mailed yielded one volunteer. Of the volunteers, 95 men were randomly allocated to be sold a middle-tar cigarette and 88 to be sold a low-tar cigarette of identical appearance. The cigarettes were sold at three different reduced prices and the men were asked to smoke them for five weeks. There was a 22% drop-out and this was unrelated to type of cigarette smoked. A reduction in price of 20% was sufficient incentive for volunteers to participate. Cigarette butts were collected weekly or fortnightly and urine samples were collected initially and after three and five weeks. Compliance with the trial cigarettes was good. The excretion of nicotine metabolites, number of cigarettes smoked and average butt weight for men allocated the low-tar cigarette was not significantly different from that of those allocated the middle-tar cigarette. This suggested that the former compensated for the 37% reduction in the nicotine yield of their cigarette by taking more frequent or deeper puffs from their cigarette. The implications of these results for a large-scale, randomized controlled trial are discussed.