Please note: In 2003, the CTF updated its Grades of Recommendations to include an "I Recommendation" for situations where insufficient evidence exists to allow a recommendation to be made.  (Formerly, these situations were captured under a "C Recommendation".)  This change is not retroactive, and all "C Recommendations" made prior to 2003 have not been reevaluated in light of the new "I" recommendation grade.  For a discussion of these recommendation grades, please link to the 2003 article in the Canadian Medical Association Journal here.

Prevention of Tobacco-Caused Disease

Objective
To make recommendations regarding prevention of disease caused by tobacco smoking through the use of primary prevention and cessation interventions.

Burden of Suffering

Trends in Smoking
The use of tobacco in Canada has declined gradually since 1965. A November 1992 survey found that 28% of Canadians over the age of 18 were smokers. It is estimated that roughly 6,700 Canadian adolescents start smoking every month. The average age for starting to smoke has been reported to be 11-13 years. High rates of tobacco use are seen among Armed Forces personnel (53% of junior navy personnel smoked in 1992) and Canadian Native peoples (59% regular smokers in 1992). A 1991 study found that 44% of the Canadian work force is exposed to second-hand smoke at work, and 54% of Canadian children live in households with at least one smoker.

Health Effects of Smoking
Tobacco use has been consistently linked with a variety of serious pulmonary, cardiovascular and neoplastic diseases. It has been estimated that there were over 38,000 smoking-attributable deaths in 1989, or 20% of all the deaths in Canada. This resulted in 271,497 potential years of life lost before 75 years of age.

Health Effects of Smoking Cessation
Tobacco is highly addictive. Over 75% of adult smokers would like to stop and at least 60% have tried to quit at some time in their lives. Approximately one-third of smokers attempt to quit every year. About 20% reported quitting on the first attempt, while 50% succeeded after 6 tries. The health benefits of smoking cessation far exceeded any risks from the average 2.3 kg weight gain or any adverse psychological effects that followed quitting.

Options
Primary options were smoking cessation counselling and referral to other programs, counselling to prevent smoking initiation, and counselling to prevent or reduce environment tobacco smoke (ETS) exposure. Smoking cessation strategies included nicotine replacement therapy, education programs and group therapy.

Outcomes
Prevalence of smoking, delay or prevention of smoking initiation and cessation/abstinence rates.

Evidence
MEDLINE was searched for 1988 to August 1993 using the keywords smoking and prevention, smoking cessation, tobacco, clinical trial or meta-analysis, Canada and physician. Additional papers were identified from the authors’ personal files. Study results were synthesized in table or graphic format only.

Values
The 13-member Task Force of experts in family medicine, geriatric medicine, pediatrics, psychiatry and epidemiology used an evidence-based method for evaluating the effectiveness of preventive health care interventions. Recommendations were not based on cost-effectiveness of options. Patient preferences were not discussed.

Background papers providing critical appraisal of the evidence and tentative recommendations prepared by the chapter author were pre-circulated to the members. Evidence for this topic was presented and deliberated upon in 1- to 2-day meetings, 2 to 3 times per year from January 1993 to June 1993. Consensus was reached on final recommendations.

Benefits, Harms, and Costs
A 1988 meta-analysis of 39 smoking cessation trials found that 1-year cessation rates were about 6% higher for participants who received a smoking cessation intervention, than for those who did not.

A 1994 meta-analysis of RCTs of nicotine replacement therapies (gum, patches, inhalers, nasal sprays) reported an overall odds ratio of 1.71 (95% CI 1.56-1.87) for abstinence among the treatment group. In another meta-analysis, efficacy of nicotine gum (2 mg) was 6% (CI 4% to 8%), and was greater in self-referred compared with invited participants (11% vs 3%). Efficacy of the patch was 9% (CI 6% to 13%).

A 1987 meta-analysis found that patients attending cessation clinics who used nicotine gum had higher 1-year abstinence rates than those who used placebo gum (23% vs 13%). In general practice settings, nicotine gum users had higher abstinence rates than those using no gum (9% vs 5%), but no differences were found between nicotine gum and placebo gum users (11.4% vs 11.7%).

3 RCTs reported improvements in 1-year cessation rates of 5% to 13% among patients using transdermal nicotine patches compared with those using placebo patches. Adverse effects of the 24-hour patch included systemic side effects or withdrawal symptoms in 32% of nicotine patch users compared with 24% of placebo patch users, and local skin problems in 14% to 50% of nicotine patch users compared with 0% to 13% of placebo patch users.

No strong evidence exists about the effectiveness of formal education programs in preventing smoking initiation. The 1994 Report of the U.S. Surgeon General, which considered evidence from meta-analyses and other sources, reported that social influence programs decreased smoking prevalence among students by 25% to 60%.

The effectiveness of physician counselling by the physician in to preventing smoking initiation has not been specifically evaluated.

In a small RCT, physician telephone and letter contact with mothers encouraging changes in household smoking (but not cessation) did not reduce infant exposure to ETS. Preschool education programs create intent to reduce ETS exposure, but other outcomes have not been measured

Recommendations
Recommendation grade [A, B, C, D, E]  and level of evidence [I, II-1, II-2, II-3, III] are indicated after each recommendation. Citations in support of individual recommendations are identified in the guideline text.

• There is good evidence to support smoking cessation counselling by physicians for all patients who smoke [A, I]. Nicotine replacement therapy may be offered as an adjunct [A, I].
• There is fair evidence to support referral to validated smoking cessation programs after cessation counselling [B, I].
• There is fair evidence to support counselling of children and adolescents to prevent smoking initiation [B, I, III].
• There is insufficient evidence to evaluate counselling to reduce exposure to ETS [C, I, II-3], but it may be helpful to include during cessation counselling.

Sponsors
The Canadian Task Force on Preventive Health Care developed this guideline with funding from Health Canada.
Selected References

Source Document
Taylor MC and Dingle JL. Prevention of tobacco-caused disease. In: Canadian Task Force on the Periodic Health Examination. Canadian Guide to Clinical Preventive Health Care. Ottawa: Health Canada, 1994; 500-11.