Because it is a more common outcome than alternative measures (Keely, Hughes, & Carpenter, 2001), it enhances statistical power. Continuous abstinence may not capture those who quit later in the process, which is a particular problem in cessation-induction studies (Velicer, Prochaska, selleckchem Nilotinib Rossi, & Snow, 1992). Most people who achieve point prevalence abstinence in a typical aid-to-cessation study have achieved long-term abstinence (Keely et al., 2001). The point prevalence rate provides an unbiased estimate of the rate of prolonged abstinence (Keely et al., 2001; Stead, Perera, Bullen, Mant, & Lancaster, 2008). For these reasons, the U.S. Public Health Service guideline on tobacco dependence uses point prevalence as the preferred outcome (Fiore et al., 2008).

Counterarguments in favor of prolonged abstinence are that the aim of smoking cessation is to get smokers to quit and stay quit forever, the only outcome known to improve health (Peto & Doll, 2006). One third of those who achieve point prevalence abstinence are not long-term abstainers (Keely et al., 2001), and this proportion might be much higher in cessation-induction studies than in aid-to-cessation studies (e.g., Aveyard, Griffin, Lawrence, & Cheng, 2003). There also has been disagreement about how to count enrolled participants who defaulted on follow-up. Some researchers advocate counting such people as smokers (Hughes et al., 2003; West, Hajek, Stead, & Stapleton, 2005), and some evidence indicates that in typical aid-to-cessation studies this is the case (Foulds et al., 1993).

Others have argued that this assumption is probably not appropriate for cessation-induction studies (Velicer, Prochaska, Fava, Laforge, & Rossi, 1999), although no empirical evidence has identified the smoking status of defaulters to follow-up in cessation-induction studies. In an effort to reconcile such differences, the SRNT working group examined these issues and the evidence and recommended that prolonged abstinence, meaning abstinence for either 6 or 12 months, be used as the primary outcome in smoking cessation studies (Hughes et al., 2003). In cessation-induction trials, outcomes should be measured at some (arbitrary) point after the start of the intervention. The period chosen should allow enough time for the intervention to induce initially unwilling quitters to begin a quit attempt.

In aid-to-cessation studies, abstinence measures are tied to the quit day. West AV-951 et al. (2005) proposed the Russell Standard measure of prolonged abstinence. The present paper describes a process for defining how prolonged abstinence is measured and what counts as a treatment success, extending the recommendations of the SRNT working group. Recently, a new approach to treating smokers has been tested in clinical trials. Smokers who did not intend to quit were randomized to either long-term nicotine replacement therapy (NRT) or placebo and given advice on how to cut down on cigarettes.