Table 2.
Association Between Baseline Nicotine Concentration and Study Outcomes
| Nicotine concentrationa | Frequency of Nicotine Product Use in Past 30 d at Follow-Up, OR (95%)b | Daily Intensity of Nicotine Product Use at Follow-Up, RR (95% CI)c | |||||
|---|---|---|---|---|---|---|---|
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| Smoking | Vaping | No. of Cigarettes Per Day | No. of Vaping Episodes Per Day | No. of Puffs Per Vaping Episode | |||
| 1–2 d | ≥3 d | 1–2 d | ≥3 d | ||||
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| Unadjusted Models | |||||||
| Low (N=52) | NA | NA | NA | NA | 2.05 (1.09, 3.01) | 2.46 (1.62, 3.30) | 2.41 (1.65, 3.18) |
| Medium (N=35) | NA | NA | NA | NA | 1.92 (1.05, 2.78) | 2.77 (1.89, 3.66) | 4.90 (4.16, 5.65) |
| High (N=21) | NA | NA | NA | NA | 14.17 (13.00, 15.33) | 3.90 (2.94, 4.86) | 3.67 (2.77, 4.57) |
| Trend effectsd | 1.21 (0.72,1.98) | 2.43 (1.58, 3.76) | 1.06 (0.69, 1.59) | 1.73 (1.24, 2.41) | 2.32 (1.50, 3.59) | 1.76 (1.33, 2.33) | 1.57 (1.18, 2.08) |
| Adjusted Modelse | |||||||
| Low (N=52) | NA | NA | NA | NA | 1.65 (0.73, 2.57) | 3.32 (2.61, 4.03) | 2.05 (1.41, 2.70) |
| Medium (N=35) | NA | NA | NA | NA | 1.63 (0.77, 2.49) | 3.32 (2.54, 4.10) | 3.39 (2.66, 4.11) |
| High (N=21) | NA | NA | NA | NA | 7.03 (6.11, 7.95) | 2.44 (1.63, 3.24) | 2.23 (1.42, 3.03) |
| Trend effectsd | 1.01 (0.54, 1.89) | 2.26 (1.28, 3.98) | 0.98 (0.59, 1.60) | 1.65 (1.09, 2.51) | 1.74 (1.27, 2.37) | 1.42 (1.09, 1.85) | 1.69 (1.14, 2.19) |
Abbreviations: e-cigarette, electronic cigarette; NA, insufficient size to calculate effects; OR, odds ratio; RR, rate ratio.
Nicotine concentration vaped at baseline indicates the regressor. No nicotine indicates 0 mg/mL; low 1 to 5 mg/mL; medium, 6 to 17 mg/mL; and high, 18 mg/mL or greater.
Polytomous (multinomial) regression model (contrast category for respective outcome: 0 days of use).
Negative binomial regression model (reference group for regressor: No nicotine [0 mg/mL]).
Nicotine concentration is a continuous predictor (scored: No nicotine = 0, low = 1; medium = 2; high = 3)
Adjusted for age, sex, race/ethnicity, highest parental educational level, baseline lifetime other tobacco product use, baseline e-cigarette or combustible cigarette topography in the past 30 days, baseline e-cigarette or combustible cigarette use in the past 30 days, baseline peer vaping, baseline peer smoking, sensation seeking, depressive symptoms, and delinquent behavior.
Sample sizes range from 170–181 for unadjusted models and 168–179 for adjusted models.