How should we define light or intermittent smoking? Does it matter?

Abstract

Multiple terms for light and intermittent smokers (LITS), each with a range of definitions, are found in the literature. Because of this wide range of terms and definitions, there has been interest in developing a standard definition of LITS. However, several factors need to be taken into account in setting such a definition. In the literature, levels of cigarette consumption often serve as a proxy measure for toxin exposure, level of addiction, or level of disease risk. However, for a variety of reasons, consumption may not be a good surrogate for these predictor and outcome measures. Some of these reasons include: differences in tobacco products that may affect exposure, changes in understanding about the levels of tobacco use that sustain addiction, how closely consumption measured as cigarettes smoked per day correlates with other markers of exposure, the effect of compensation (changes in smoking behavior to adjust for changes in nicotine levels or in volume of cigarettes smoked), the nonlinear relationship between consumption and disease risk for some diseases, whether people maintain the same levels of smoking over time, and the meaningfulness of various levels of cigarette consumption if other tobacco products are used concurrently. Public health will need to consider, in light of these factors, whether a categorization of LITS is warranted. This commentary briefly explores each of these aspects of LITS: (a) the terms used in the literature for LITS and the range of definitions found for each term; (b) the most valid LITS categories based on the stability of the various levels of consumption over time; (c) the validity of using consumption as a surrogate measure of toxin exposure, addiction, disease risk, or program impact; (d) the implications of polytobacco use for consumption being used as such a proxy; and (e) whether better measures exist for exposure, addiction, and disease risk. Finally, recommendations regarding the use of consumption as a predictor or as an outcome variable and possible relevant categorizations are discussed.