Transitions in smoking status over time in a population-based panel study of smokers

Abstract

Introduction: Few studies have examined the transitions of smokers in the general population through multiple periods of daily, occasional smoking, or abstinence over time. Transitions from daily to occasional smoking are particularly of interest as these may be steps toward cessation.

Methods: The Ontario Tobacco Survey panel study followed 4,355 baseline smokers, semiannually for up to 3 years. Probabilities of all possible changes in smoking status more than 6 months were estimated using 13,000 repeated measures observations generated from sets of 3 consecutive interviews (n = 9,932 daily smokers, 1,245 occasion smokers, and 1,823 abstinent for at least 30 days, at Time 1).

Results: For initial daily smokers, an estimated 83% remained daily smokers more than 2 follow-ups. The majority of those who had been abstinent for 30 days at 1 interview, were also former smokers at the following interview. In contrast, occasional smoking status was unstable and future smoking status was dependent upon smoking history and subjective dependence. Among daily smokers who became occasional smokers 6 months later, an estimated 20% became a former smoker, at the next interview, but 50% returned to daily smoking. Daily, turned occasional smokers who rebounded back to daily smoking were more likely to describe themselves as addicted at Time 1. Continuing occasional smokers were somewhat less likely to intend to quit, or have tried, despite considering themselves less addicted.

Conclusions: Reducing to occasional smoking can be a stepping stone toward cessation but entails a greater risk of return to daily smoking, compared with complete abstinence.

Figure 1.

Estimated probabilities* of the same (solid arrows) or different (dashed arrows) smoking status over consecutive interviews. Repeated measures analysis of 13,000 triads of consecutive interviews in a population-representative sample of smokers in the Ontario Tobacco Survey smokers cohort. *Conditional probabilities as percentages. Probabilities of transition from Time 1 to Time 2 sum to 100% by smoking status at Time 1. Values in italics are the percentage of participants who reported unchanged consumption over the entire 6-month period. Estimated probabilities from Time 2 to Time 3 are conditional, and sum to 100% within each unique combination of Time 1 and Time 2 status. The percentage of participants following a specific path from Time 1 to Time 3 may be estimated using the product of conditional probabilities. For example, the percentage of daily smokers, at Time 1, who remain daily smokers over two interviews is 0.91 × 0.92 = 0.837 or approximately 84%. Percentages may not add to 100 due to rounding.