Long-term follow-up of a high- and a low-intensity smoking cessation intervention in a dental setting--a randomized trial.

Background: Achieving lifelong tobacco abstinence is an important public health goal. Most studies use 1-year follow-ups, but little is known about how good these are as proxies for long-term and life-long abstinence. Also, intervention intensity is an important issue for development of efficient and cost-effective cessation treatment protocols.The study aims were to assess the long-term effectiveness of a high- and a low-intensity treatment (HIT and LIT) for smoking cessation and to analyze to what extent 12-month abstinence predicted long-term abstinence.

Methods: 300 smokers attending dental or general health care were randomly assigned to HIT or LIT at the public dental clinic. Main outcome measures were self-reported point prevalence, continuous abstinence (≥6 months), and sustained abstinence. The study was a follow-up after 5-8 years of a previously performed 12-month follow-up, both by postal questionnaires.

Results: Response rate was 85% (n=241) of those still alive and living in Sweden. Abstinence rates were 8% higher in both programs at the long-term than at the 12-month follow-up. The difference of 7% between HIT and LIT had not change, being 31% vs. 24% for point prevalence and 26% vs. 19% for 6-month continuous abstinence, respectively. Significantly more participants in HIT (12%) than in LIT (5%) had been sustained abstinent (p=0.03). Logistic regression analyses showed that abstinence at 12-month follow-up was a strong predictor for abstinence at long-term follow-up.

Conclusions: Abstinence at 12-month follow-up is a good predictor for long-term abstinence. The difference in outcome between HIT and LIT for smoking cessation remains at least 5-8 years after the intervention.

Trial Registration Number: NCT00670514.