Retrospective analysis of changing characteristics of treatment-seeking smokers: Implications for further reducing smoking prevalence

Objective: The goal of the current study was to empirically compare successive cohorts of treatmentseeking smokers who enrolled in randomised clinical trials in a region of the USA characterised by strong tobacco control policies and low smoking prevalence, over the past three decades. Design: Retrospective treatment cohort comparison. Setting: Data were collected from 9 randomised clinical trials conducted at Stanford University and the University of California, San Francisco, between 1990 and 2013. Participants: Data from a total of 2083 participants were included (Stanford, n=1356; University of California San Francisco, n=727). Primary and secondary outcomes: One-way analysis of variance and covariance, χ² and logistic regression analyses were used to examine relations between nicotine dependence, cigarettes per day, depressive symptoms and demographic characteristics among study cohorts. Results: Similar trends were observed at both settings. When compared to earlier trials, participants in more recent trials smoked fewer cigarettes, were less nicotine-dependent, reported more depressive symptoms, were more likely to be male and more likely to be from a minority ethnic/racial group, than those enrolled in initial trials (all p's<0.05). Analysis of covariances revealed that cigarettes per day, nicotine dependence and current depressive symptom scores were each significantly related to trial (all p's<0.001). Conclusions: Our findings suggest that more recent smoking cessation treatment-seeking cohorts in a low prevalence region were characterised by less smoking severity, more severe symptoms of depression and were more likely to be male and from a minority racial/ethnic group.