Does e-cigarette nicotine strength influence substitution for combustible cigarettes?

Abstract

Using the Experimental Tobacco Marketplace, we examined the effects of e-liquid freebase nicotine strength (3-24 mg/mL) and e-liquid price (US$0.25-$1.00/mL) on behavioral economic substitution for cigarettes in dual cigarette/e-cigarette (n = 41) and exclusive cigarette (n = 40) users. Subjective effects of nicotine strength were also examined. All nicotine strengths served as a substitute for combustible cigarettes, with greater substitution observed in dual users. When analyzing e-liquid volume purchased (mL), nicotine strength did not influence substitution; however, when analyzing e-liquid nicotine purchased (mg), degree of substitution increased as a function of nicotine strength. Additionally, higher nicotine strengths reduced the volume and probability of e-liquid purchasing, increased cigarette demand, and produced less favorable subjective effects than lower strengths. Increasing e-liquid price reduced e-liquid purchasing and did not influence substitution. We conclude that nicotine strength does not robustly affect the degree to which e-liquid substitutes for cigarettes, as no effect was observed in analysis of the unit of purchase most relevant to real-world sales (volume). Instead, high-strength nicotine potentially reduces the appeal and probability of purchasing e-liquid. Future work should examine these effects in nicotine salt-based e-liquids compared with freebase nicotine (used here) and in choice contexts with concurrent access to different nicotine strengths.

Keywords: cigarettes; demand; e‐cigarettes; nicotine; substitution.

FIGURE 1

Participant flow diagram.

FIGURE 2

Observed mean (±SEM) cigarette own‐price demand curves, by condition and group. The 3–24 mg/mL labels refer to the nicotine strength of e‐liquid.

FIGURE 3

Estimated marginal means (±SEM) from linear mixed‐effects modeling showing significant effects of e‐liquid nicotine strength on intensity (Q _$0.25) and peak expenditure (O_Max ) in own‐price cigarette demand. Significant effects of e‐liquid nicotine strength on both cigarette own‐price intensity (p < .05) and peak expenditure (p < .01) were observed. No pairwise comparisons between individual nicotine strengths were significant.

FIGURE 4

Observed mean (±SEM) e‐liquid cross‐price demand curves calculated using volume purchased (mL) and nicotine purchased (mg), by condition and group. The 3–24 mg/mL labels refer to the nicotine strength of e‐liquid.

FIGURE 5

Estimated marginal means (±SEM) from linear mixed‐effects modeling showing significant interactions in cross‐price e‐liquid demand. In analysis of e‐liquid volume purchased, significant interactions were observed between e‐liquid strength and e‐liquid price, group and e‐liquid price, and group and cigarette price (all ps < .01). In analysis of e‐liquid nicotine purchased, these significant interactions were replicated (all ps < .01), with additional significant interactions observed between group and cigarette price (p < .0001) and group and nicotine strength (p < .0001; data not shown). Data points are displaced slightly on the x‐axis, for clarity.

FIGURE 6

Estimated marginal means (±SEM) from linear mixed‐effects modeling showing scores on the Drug Effects/Liking Scale (DELS) for each e‐liquid nicotine strength, by group. Higher scores reflect a more positive subjective drug response. Significantly higher scores were observed in the dual use than in the cigarette use group, and significantly lower scores were observed at the 24‐mg/mL strengths than at all other strengths.