Duration of smoking abstinence and success in quitting

For most smokers, quitting is a difficult process. Many smokers try to quit repeatedly before they succeed, with some relapsing even after a lengthy period of abstinence. Few population-based cohort studies have examined relapse among former smokers. Quantification of the relationship between the duration of abstinence and the likelihood of continued abstinence is important for the evaluation of ongoing public health interventions and the design of smoking-cessation programs.

We analyzed longitudinal data from a large, representative population cohort of former smokers and estimated the probability of future relapse for different durations of abstinence at baseline (e.g., 1 to <3 months and 3 to <6 months).

From the 1990 California Tobacco Survey that used a random-digit-dialed computer-assisted telephone survey to interview 24296 California adults (baseline interview) from June 1990 through February 1991, a stratified random sample of 4642 adults was reinterviewed from March 1992 through July 1992. Both surveys assessed smoking status using standard questions about the lifetime use of 100 cigarettes and the self-classification of current smoking: 1) "Have you smoked at least 100 cigarettes in your lifetime?" and 2) "Do you smoke cigarettes now?" We included all 1449 former smokers at baseline interview who answered "yes" to the first question and "no" to the second and who also provided a valid date at both of the surveys when asked, "When did you last smoke regularly?" All data were weighted to account for the study design and to ensure that the estimates were representative of the California population by age, sex, race/ethnicity, education, and geographic region.

Only about 12% of the former smokers who had quit for less than 1 month at baseline remained continuously abstinent at the follow-up interview. This percentage increased to 25% for those who had quit from 1 to less than 3 months; it increased again to 52% if the duration of quitting was from 3 to less than 6 months, but it increased only slightly to 59.2% for those who had quit from 6 to less than 12 months. Overall, the likelihood of remaining continuously abstinent until the follow-up interview was about 90% for former smokers who had quit for 3 months or longer and 95% for those who had quit for 1 year or longer.

We suggest that self-reported cessation for more than 3 months be considered as an intermediate criterion for success both in longitudinal studies and the cross-sectional evaluation of community interventions. If a more stringent criterion is needed, we recommend self-reported cessation for at least 1 year.