Patterns of intermittent smoking: An analysis using Ecological Momentary Assessment

Abstract

Non-daily smokers comprise a substantial proportion of US smokers, but there has been little study of their patterns of smoking, which are often assumed to reflect “social smoking.” We used Ecological Momentary Assessment methods to study smoking patterns in 27 non-daily smoking adults who recorded each cigarette smoked over three weeks by leaving a voice mail message indicating their circumstances at the time of smoking. All told, 689 cigarettes were recorded over 589 person-days of observation. On average, participants smoked on 67% of days, averaging 2.1 (SD = 0.91) cigarettes per day on days they smoked; 22% of all cigarettes were smoked in bouts (within an hour of another cigarette). Altogether, 19% of cigarettes were smoked when drinking alcohol and 29% when participants were socializing. Smoking patterns varied widely across participants. A pair of hierarchical cluster analyses distinguished three groups: Those who smoked primarily (81% of cigarettes) in the daytime (Early smokers; n = 15, 58% of total sample), those who smoked primarily (75% of cigarettes) at night (Late smokers; n = 7, 27%), and a distinct, classic “Social smoking” group (n = 4, 15% of total sample), who smoked mostly at night but also primarily when socializing or drinking (86% of their cigarettes), in the evening (71% of their cigarettes), on weekends (65% of their cigarettes), and in bouts (71% of their cigarettes). Overall, results suggest that non-daily smoking patterns are quite heterogeneous, and that many non-daily smokers may not be primarily social smokers.

Introduction

The dominant model of smoking posits that cigarette smoking is maintained by nicotine dependence, which drives smokers to smoke at regular and frequent intervals in order to maintain adequate nicotine concentrations and thus avoid lapsing into nicotine withdrawal (Stolerman & Jarvis, 1995). However, changes in population smoking patterns have challenged this account. The traditional account explains the typical pattern of smoking seen in the US, where smokers smoke every day, averaging approximately 20 cigarettes per day (CPD), or more than one cigarette every waking hour (Al-Delaimy et al., 2007). However, US smoking patterns are changing. According to some national surveys (e.g., BRFSS; Centers for Disease Control, 2003, NHSDA, 2002), 25–33% of adult US smokers do not smoke every day (though see Hassmiller et al., 2003, Wortley et al., 2003). Non-daily, or intermittent, smoking is becoming a significant smoking pattern, at least as common as heavy smoking (25+ CPD; CDC, 2005). Further, intermittent smoking seems to be increasing steeply; its prevalence has increased by 40% over 6 years (CDC, 2003; though see CDC, 2006). Shiffman (in press) has suggested that the recent emergence of this smoking pattern is related to increasing restrictions on smoking, including both smoking regulations and the increasing cost of cigarettes. Thus, it seems important to understand intermittent smokers (ITS) and their smoking patterns.

Non-daily smoking has received the most attention among young smokers (e.g., Leatherdale, Ahmed, Lovatco, Manske, & Jolin, 2007), who are at early developmental stages of smoking, but intermittent smoking is not limited to young smokers. Adult ITS are, on average, only 1–2 years younger than daily smokers, averaging 39 years of age (Wortley et al., 2003). Similarly, while many ITS may be in the process of either escalating or reducing their smoking, intermittent smoking is not always a transitional stage: ITS smoking can be stable across time (Hassmiller et al., 2003).

Survey research gives us a window into the demographic characteristics of ITS, but does not shed light on their smoking patterns — that is, it does not help us to understand when and why ITS actually smoke. While almost no data are available, authors have often assumed that ITS are “social smokers” who smoke when others are smoking, for social reasons (Oksuza, Mutlua, & Malhanb, 2007), and whose smoking is associated with “partying” and alcohol consumption (Dierker et al., 2006, Philpot et al., 1999, Stanton et al., 1996), often in bars and nightclubs (Biener and Albers, 2004, De Vries et al., 2007). It is known that the tobacco industry has sought to promote such social smoking (Katz & Lavack, 2002). Among college students, global reports suggested that most non-daily smokers are social smokers (Moran, Wechsler, & Rigotti, 2004), but it is not clear whether this adequately characterizes adult ITS smoking, or whether other smoking patterns and contexts might also be important in ITS.

Studies among a related group of smokers — “chippers,” who smoke daily or nearly daily, but smoke at very low rates — have yielded mixed results on social smoking. On questionnaires, chippers reported more social motives for smoking (Kassel, Shiffman, Paty, Gnys, & Zettler-Segal, 1994). However, the validity of such questionnaire measures has been questioned (Shiffman, 1993), and data collected in real time by palmtop computers using Ecological Momentary Assessment (EMA, Stone and Shiffman, 1994, Stone et al., 2007) suggested different conclusions: While chippers' smoking was concentrated in the evenings, and chippers were more likely to smoke when drinking and when others were smoking, chippers smoked many of their cigarettes when alone, and outside of “indulgent” contexts like parties (Shiffman & Paty, 2006). It is not clear how these findings on chippers, based on data collected over 20 years ago, might apply to the current population of ITS, whose emergence seems to have been fueled by the recent surge of restrictions on smoking (Shiffman, in press). Thus, detailed studies examining the smoking patterns of contemporary ITS are needed.

In this paper, we report an initial exploratory study examining patterns of cigarette consumption in ITS, using real-time recording of smoking (Stone & Shiffman, 2002). Our aim was primarily descriptive — to describe how ITS smoking is distributed over time and situations, and to assess variations in smoking patterns, by classifying subtypes of smokers, both by time of day and by pattern. The temporal distribution of smoking can be informative; for example, smoking in the morning is associated with dependence (Fagerstrom, 2003, Toll et al., 2007), whereas evening smoking and smoking on weekends might be associated with non-dependent social smoking (Grimshaw et al., 2003). We also explored the temporal and situational patterning of smoking: Social smokers might be expected to concentrate their smoking in bouts, associated with social situations when they have been drinking.