Primary care centers can play a very important role in helping people to stop smoking. There is a large body of research on the effectiveness of specific interventions especially addressed to people who want to stop smoking. In addition to that, there are no studies with a large sample of individuals included that tested the complete range of interventions recommended nowadays for helping people in the different smoking cessation stages of change and with different degrees of physical and psychological dependence, especially including motivational interviewing in those not interested in cessation in the very next weeks. This study will test a complex intervention that at first classifies smokers in stages and after that treats every smoker according to what stage he/she is in at the moment, his/her degree of dependence and his/her own characteristics.

OBJECTIVES:

• To evaluate the effectiveness of a stepped smoking cessation intervention based on a transtheoretical model of change that uses the pharmacological and no-pharmacological methods proposed by evidence based Clinical Practice Guidelines for smoking cessation from primary care centers.
• To assess the health status change in relationship with the smoking cessation process.

DESIGN: Cluster randomized clinical trial

Unit of Randomization: Care basic unit (family physician or nurse that cares for the same group of patients). Intention to treat analysis.

PARTICIPANTS: 2911 smokers (ages 14-75 years) consulting for any reason to primary care centers

INTERVENTION: 6-month implementation of recommendations of a Clinical Practice Guideline that includes motivational consulting for smokers at the precontemplation - contemplation stage; brief intervention for smokers in preparation-action who do not want help; intensive intervention with pharmacotherapies for smokers in preparation-action who want help; and reinforcing intervention in the maintenance stage.

CONTROL: Usual care

MEASUREMENT: Self reported abstinence confirmed by an expired air carbon monoxide concentration of 10 parts per millions or less; Point prevalence at the end of intervention, 1 and 2 years after the beginning of intervention; Continuous abstinence rate for 1 year; Change of stage in the smoking cessation process; Health status measured by SF-36.

Inclusion Criteria:

• Smokers
• Accept participation and follow-up by phone interviews for 2 years

Exclusion Criteria:

• Terminal illness
• Active addictive behaviours or important health problems