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} However, there are constraints on effective health promotion by primary healthcare professionals, particularly lack of time and skills.³ Consequently effective, low cost interventions in primary care that require only minimal input from health professionals should be sought.

Two studies in North America investigated computer generated personalised letters as a method of encouraging smoking cessation. ^{4 5} Such letters allow smokers to receive expert input without much demand on health professionals' time. The findings were positive but can only be regarded as preliminary. The numbers of participants were small, and in neither study were smokers' claims to have stopped smoking validated biochemically. We were encouraged by the results of these studies, but believed that a larger study, with biochemical validation, was needed on a population with a wider socioeconomic range.

We hypothesised that computer tailored letters would be more effective and cost effective than non-tailored letters in helping smokers to stop. We planned subgroup analyseslight versus heavy smokers, and intention versus no intention to quit in the next six monthsbecause the two previous studies had indicated differential effects according to heaviness of smoking and readiness to quit.

	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 that asked 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

How the letters were tailored

Overall structure of the letters
Letters were printed on four A5 sized pages (one piece of A4 paper folded in half). The front page contained introductory text and the middle pages contained most of the tailored information. The back page was selected from 16 possible versions. Information was tailored on two levels: overall content was based on category of smoker, while specific text within sections was determined by each participant's specific answers to the questionnaire.

Categories of smoker
Smokers' "stage of change" was determined using the standard questions "Are you intending to stop smoking in the next six months?" (No = a "pre-contemplator") and "If yes, are you intending to stop smoking within the next month?" (No = a "contemplator", yes = a "preparer").

Content of the letters
All the letters apart from those for smokers in category 1 were based on five possible sections.

• A comment on the reasons given for liking and disliking smoking
• A paragraph on each of the three most important reasons for disliking smoking
• A health message for those with serious respiratory or circulatory conditions.
• (3) Confidence building, with three possible parts:

• A general message on confidence
• Specific reasons for being confident
• Advice on coping with the three main difficulties envisaged when stopping.
• (4) Advice on stopping:

• "Small steps": three changes to try in the next month in preparation for stopping
• Ideas of what to do when planning to stop smoking, eg pick a date, tell friends
• "Go for it": list of things that other people have found useful when they have tried to stop.
• (5) Closing section, reiterating the main emphasis of the letter.
• Table 1 shows which sections were selected for categories 2-7. The detailed content of each section was tailored according to the answers in individual questionnaires.

Focus of information for each category
Category 1The letter acknowledged that the participant was not currently interested in stopping smoking. If participants were concerned about their health some information was given about how stopping smoking would improve their health. Reasons to be confident of successfully stopping were listed. If the participant was a heavy smoker, the use of nicotine replacement was recommended should they eventually try to stop.

Second level tailoring
Within each section, inclusion of text was based on participants' answers to the questionnaire. The following are examples of tailoring at this level.

• The level of importance of the confidence messages was determined by how confident the person felt about stopping smoking. If they were not at all confident, the confidence messages were given a high level of importance.
• Reasons for liking and disliking smoking were itemised; these were based on the participant's answers.
• The three main barriers that make it difficult for a participant to stop were inferred from answers to questions about the difficulty of stopping, reasons for returning to smoking, and what they liked about smoking. The text aimed to provide support in overcoming these barriers.
• The age and sex of a participant were taken into consideration when ideas about types of exercise they might like to take were given.

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 covering letter, 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
The unit of randomisation was the individual participant. After the questionnaires and consent forms were returned, we randomised the participants 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, defined as a negative response to the question "Have you smoked a cigarette, even a puff, in the last seven days?" We validated self reports of smoking cessation by salivary cotinine assay.⁸ 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. Data on continuous variables were tabulated as means and standard deviations. Differences between groups were assessed by using analysis of variance. We used multiple logistic regression to assess relations between outcomes and group membership.¹² 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. Multiple logistic models tested for interaction terms for heaviness of smoking by group and initial stage of change by group. Logistic models were assessed for each of the four subgroups defined by heaviness of smoking (<20 and 20 cigarettes per day) and initial stage of change (pre-contemplator and contemplator or preparer).

	Results

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Response rates and overall cessation rates
Figure 1 shows the flow of participants through the study. The number of valid mailings after exclusion of those sent to the wrong address or to participants who were currently non-smokers or who were excluded was 6155. 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).

View larger version (28K): [in this window] [in a new window]   Flow of participants through the study

Characteristics of respondents
There were no significant differences between the groups in age, sex, level of social deprivation, or initial stage of change. The percentage of heavy smokers was significantly higher in the tailored letter group than in the non-tailored letter group, which had the lowest proportion of heavy smokers.

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 2).

Shift in stage of change among participants who did not stop smoking
Among participants who did not stop smoking, heavy smokers who received the tailored letter were 76% more likely (11% to 180%) to have made a positive shift in stage of change compared with those who received no letter (table 4).

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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Our main finding was that, compared with no letter, the non-tailored letter was effective and cost effective in helping smokers to stop smoking, whereas the computer tailored letter was not. However, the computer tailored letter encouraged heavy smokers to move forward in their stage of readiness to consider stopping smoking.

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. ^{4 5 14} 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,¹⁵ 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.⁴ 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.¹⁶ 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%.¹⁷ 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, using a weaker concept of tailoring, 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, given the evidence from the British Thoracic Society's study that a non-tailored letter signed by a physician is more effective than an unsigned control letter.¹⁷

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. ^{14 20-22} 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).¹⁴ 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, ^{16 23} but its implementation is limited by various constraints on health professionals.³ 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.