This is the first detailed study of ITS's smoking patterns using cigarette-by-cigarette data collected in smokers’ natural environments. The results give some insight into ITS's smoking patterns, and their variability. The majority of ITS’ cigarettes were smoked in the morning and afternoon, rather than evening or night, most were smoked singly, rather than in bouts, and most were not reported to be associated with drinking or socializing. Cluster analysis did identify a group of ITS who could clearly be characterized as “social smokers,” but these constituted only a small proportion (11%) of subjects in this sample. The findings were not consistent with the expectation that ITS are “social smokers” (e.g., Moran et al., 2004
; Philpot et al., 1999
ITS smoking varied considerably over time. Runs of abstinence were common, with 37% of ITS abstaining for at least 5 days in a row. Conversely, runs of smoking were not rare: over a quarter (26%) of ITS smoked at least seven days in a row. Smoking was also distributed unevenly within days: 20% of all recorded cigarettes were concentrated in bouts (i.e., within an hour of another cigarette), which especially characterized cigarettes smoked when drinking and socializing. This suggests that social drinking provokes concentrated bouts of smoking in some ITS. The association between drinking and smoking is well-established, especially for light, non-dependent smokers (Kirchner & Sayette, 2007
; Shiffman & Paty, 2006
Even more striking was the variability among different ITS individuals. Some ITS smoked almost every day for 21 days, while others smoked only two days per week. On days when they smoked, some ITS averaged just one cigarette, while others averaged as many as five cigarettes per day. Some ITS smoked almost all their cigarettes on the weekends, while others did not smoke at all on weekends; some smoked almost all their cigarettes in the evening, others never smoked in the evening; some smoked most of their cigarettes in bouts, others were never observed smoking two cigarettes within an hour of each other. The wide between-subject variability strongly suggests that no single pattern characterizes ITS smoking.
Drawing on the heterogeneity of ITS smoking, we identified distinct groups of ITS based on temporal patterns. An unexpected group was the Early smokers, who constituted the majority of the sample: They frequently smoked in the morning and afternoon, but seldom at night, and they seldom smoked while drinking or socializing, or when others were smoking. Moreover, they were less likely to smoke on weekends compared to weekdays. Though they make up the majority of ITS, Early smokers seem to be the antithesis of “social smokers.”
The cluster analyses did identify a subgroup who seems to fitthe expected profile of a Social smoker. These smokers smoked mostly away from home, on the weekends, at night, while drinking and socializing. Their smoking was concentrated in bouts, and they smoked just two days a week on average, mostly on the weekend, with even the longest runs averaging less than three days in a row. However, this group constituted only 10% of the ITS sample studied here. While this was a small convenience sample, and thus the population proportions may be different, this suggests that social smoking is unlikely to be typical of ITS.
The study was subject to several limitations. It was based on a small convenience sample of ITS, and its generalizability is uncertain. The study analyzed data on the situational contexts of smoking, but lacked comparative data on non-smoking situations, which would be necessary to draw inferences about associations between smoking and context (Paty, Kassel, & Shiffman, 1992
). We also did not compare reports from ITS with reports from daily smokers; that contrast may be informative (cf. Shiffman & Paty, 2006
). The situational data were drawn from relatively unstructured qualitative reports, which are subject to participants’ decisions about what to report. Monitoring may have been reactive, causing participants to change their smoking behavior, e.g., smoking more or less than usual. Finally, although participants reported they had made timely recordings of all their cigarettes, we could not verify their compliance, and non-compliance could sway the findings, for example if participants omitted cigarettes when drinking alcohol.
On the other hand, this is the first study to examine contemporary ITS smoking in detail, and used electronically time-tagged real-time reports of individual smoking episodes, which helps overcome problems of retrospection (Stone & Shiffman, 2002
) and of back-filling of paper diaries (Stone, Shiffman, Schwartz, Broderick, & Hufford, 2003
). The time-tagging of smoking episodes was particularly useful for assessing the temporal distribution of cigarettes and the clustering of cigarettes within bouts of smoking. Population surveys querying prototypical behaviors of the different types of ITS (e.g., On the days that you do smoke, how likely are you to smoke before noon?) could help identify such patterns in broader populations. However, research on questionnaire measures of smoking patterns suggests that global survey questions may not be able to capture such patterns (Shiffman, 1993
This preliminary study provided some initial insight into ITS smoking patterns. Some ITS smoking conformed to “social smoking” stereotype — late weekend night bouts of smoking while drinking and socializing. However, the majority of ITS smoking occurred during the day, even the morning, and in the absence of either socializing or alcohol. It seems clear that the smoking patterns and motives for ITS are diverse, and deserving of further study.