Introduction

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Cigarette smoking continues to be a major preventable source of illness and premature death in Scotland. Intensive, expert-led interventions have relatively high success rates but reach only a small proportion of smokers. The real potential for reducing the national prevalence of smoking lies in the widespread implementation of brief interventions. ^{1 2}

Two studies in North America investigated computer generated personalised letters as a method of encouraging smoking cessation. ^{3 4} The numbers of participants, however, were small, and in neither study were smokers' claims to have stopped smoking validated biochemically. We believed that a larger study, with biochemical validation, was needed on a population with a wider socioeconomic range.

	Methods

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Our randomised controlled trial compared the effect on smoking cessation of a computer tailored letter, a non-tailored letter, and no letter. Ethical approval was obtained from the Grampian joint ethical committee.

Interventions
At the start of the study we sent all participants a questionnaire asking about their current smoking behaviour, attitudes to smoking, perception of barriers to quitting, and intention to quit in the next six months or in one month. After we received their questionnaire, we sent each participant a computer tailored letter, a non-tailored letter, or just a letter thanking them for participating in the study ("no letter").

Tailored letter

Non-tailored letter

No letter

Recruitment
We recruited participants from smokers aged 17 to 65 years registered at six general practices in Aberdeen. From the computerised records of the practices we identified 7427 patients, who were sent a consent form and a questionnaire to collect information to form the basis of the tailoring. We sent two reminders at intervals of three weeks.

Assignment and mailing of the letters
After the questionnaires and consent forms were returned, we randomised the participants individually to the groups using computer generated random numbers. We mailed materials appropriate to each group immediately after randomisation.

Follow up
Follow up at six months was by postal questionnaire, with two reminders at intervals of three weeks. We attempted telephone follow up of non-respondents.

Outcome measures
The main outcome measure was point abstinence at six months. We validated self reports of smoking cessation by salivary cotinine assay.⁷ Participants lost to follow up and those whose report of cessation could not be confirmed biochemically were classed as continuing smokers.

Methods of analysis
We used ² tests to analyse categorical variables. Differences between groups were assessed by using analysis of variance. We used multiple logistic regression to assess relations between outcomes and group membership.¹¹ Analyses were adjusted for age, sex, level of social deprivation, heaviness of smoking, time to first cigarette of the day, and initial stage of change.

	Results

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Response rates and overall cessation rates
Of the 6155 valid mailings, 2612 responses were valid (42.4%). A total of 2553 participants did not withdraw, and the follow up rate was 78.1% (1995/2553). A total of 154 (6.0%) participants claimed to have stopped smoking after the intervention. Salivary samples for biochemical validation were obtained from 99 participants. Eighty nine participants were validated as having stopped smoking, giving an overall validated cessation rate of 3.5% (89/2553).

Characteristics of respondents
The groups were similar in age, sex, level of social deprivation, and initial stage of change. The percentage of heavy smokers was higher in the tailored letter group than in the non-tailored letter group.

Outcomes
Sex, age, and heaviness of smoking were not associated with cessation, but there was a significant inverse association with level of social deprivation. Participants whose initial stage of change was contemplator or preparer were more likely to have stopped than pre-contemplators, as were participants who had their first cigarette later in the day (table 1). Validated cessation rates were 3.5% (30/857; 95% confidence interval 2.3% to 4.7%) in the tailored letter group, 4.4% (37/846; 3.0% to 5.8%) in the non-tailored letter group, and 2.6% (22/850; 1.5% to 3.7%) in the control group. After adjusting for confounding variables, we found that participants receiving a non-tailored letter were 66% more likely to have quit than those receiving no letter. After adjustment for confounding variables, participants who received either a tailored or non-tailored letter were 53% more likely to have quit than those receiving no letter.

Economic evaluation

Cost effectiveness of the non-tailored letter intervention
Thirty seven of the 846 participants who received a non-tailored letter stopped smoking, compared with 22 of the 850 participants who received no letter. Costs based on the actual number of participants recruited indicate that these 15 additional quitters were gained at a total cost of £464.

	Discussion

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The cessation rate of 4.4% is low compared with rates of 19% and 25% in two previous studies of computer generated letters and 21% in a mass media intervention by the Health Education Board for Scotland. ^{3 4 13} However, our study had methodological strengths: it was carried out on a randomly chosen population who had not actively volunteered to take part in the intervention and had no special motivation to quit; it used an intention to treat analysis, with all participants lost to follow up being classed as continuing smokers; claims of participants to have stopped smoking were biochemically validated; and the tailored and non-tailored letters were created from the same text base.

In contrast, the high rates of cessation in the other studies were based on self reported cessation, and subjects who dropped out were omitted from the calculations of rates of continuing smoking. In some studies the form of the materials used for the control group was very different from that in the tailored intervention. None of these studies used biochemical validation of non-smoking. Contrary to the argument that biochemical validation is unnecessary in brief intervention studies,¹⁴ our findings indicate that not validating cessation results in an overestimate of cessation. Furthermore, one study based its success rate on a subgroup of light smokers who had intended to quit smoking.³ If we had used these methods, our rate of cessation would have been 20% or more.

Raw et al summarised evidence on the validated effect of different types of cessation intervention.¹⁵ The most effective is nicotine replacement therapy, which increases the rate of cessation by 8% at six months. Brief advice from a doctor increases abstinence at six months by 2-3%. Two validated studies by the British Thoracic Society found that up to three personalised but non-tailored letters, from doctors to outpatients in chest clinics, increased cessation by 2-3%.¹⁶ The present study has found that even one short non-tailored letter from a patient's general practice is as effective as these last two brief interventions.

Can we conclude that tailored letters are not effective?
Our hypothesis that tailored letters would be more effective than non-tailored letters was not supported by the findings. However, we might consider that our non-tailored letter was in fact tailoredor at least personalisedto some extent. Although the non-tailored letter was not tailored to individuals, it was more personal than a general leaflet giving advice on smoking cessation: it was in a letter format, with the crest of the local university and the logo of the patient's general practice, and was ostensibly from "the practice." This degree of personalisation may account for some of its effect.¹⁶

Cost effectiveness of the non-tailored letter
The cost per quitter of the non-tailored letter is estimated at between £37 and £89, which compares very favourably with other cessation interventions. ^{13 18-20} The cost effectiveness ratio of the Health Education Board for Scotland's mass media intervention was between £168 and £369, corresponding to a cost per discounted life year saved of between £304 and £656 (1993 prices).¹³ However, as pointed out above, this intervention used self reported quitting. If the true rate of quitting were lower, the corresponding cost effectiveness would also have been lower.

The potential for implementation of the non-tailored letter intervention
Intervention by primary care professionals in the form of brief opportunistic advice increases smoking cessation by about 2-3% over control intervention, ^{15 21} but its implementation is limited by various constraints on health professionals.²² In contrast, the 2% increase in cessation found in the present study could be widely and easily realised by using the computerised data now usually held by general practices. Indeed, the quantity and quality of data on smoking held in general practices are set to improve as computers become more user friendly. Soon most practices will be capable of implementing this type of intervention, which would be well suited to implementation at the level of primary care groups or local healthcare cooperatives, and which could be part of a national strategy on smoking cessation. Coordinators from the smoking cessation services that have recently been set up in all health authorities and boards could play a central role.