Epidemiological evidence on count processes in the formation of tobacco dependence.

INTRODUCTION: Large-sample epidemiological studies of tobacco cigarette smoking routinely assess so-called "lifetime prevalence" of tobacco dependence. This work delves into the earliest stages of smoking involvement, focusing on newly incident tobacco cigarette smokers in the very recent past, and examines hypothesized subgroup variation in count processes that become engaged once smoking starts. Here, the term "count process" has two components: (a) whether smoking will be persistent and (b) the rate of smoking, conditional upon membership in a latent class of smokers who will persist, as estimated under the zero-inflated Poisson (ZIP) model for complex survey data.
METHODS: We estimate these ZIP parameters for nationally representative samples of newly incident smokers in the United States (all with smoking initiation within 24 months of assessment). Data are from the 2004-2007 National Surveys on Drug Use and Health.
RESULTS: Once cigarette smoking started, roughly 40%-45% persisted, and the estimated median rate was five smoking days/30 days, conditional on membership in the latent class of persistent smokers. Among non-Hispanic recent-onset cigarette smokers, Whites, Black/African Americans, Asians, and Native American/Alaskan Natives did not differ, but recent-onset smokers of Hispanic origin and those of Pacific Islander background had comparatively less cigarette involvement. DISCUSSION: Tobacco prevention and control initiatives may require elaboration in the form of brief interventions, including interpersonal and social transactions that might constrain a mounting frequency of days of smoking before daily smoking starts, and until conventional smoking cessation medication aids become indicated. These very-early stage interventions (VESI) might be mounted within family or peer groups or in the primary care or school settings, but randomized trials to evaluate VESI interventions will be required.