Table 1.
Characteristics Between Follow-Up Exclusive E-Cigarette Users and Poly Users
| Characteristics | Exclusive e-cigarette users at follow-up (n=412) |
Poly users (e-cigarette and other tobacco products) at follow-up (n=59) |
p-valuea | ||||
|---|---|---|---|---|---|---|---|
| Baseline | Follow-up | p-valueb | Baseline | Follow-up | p-valueb | ||
| Age (years), mean (SD) | 41.2 (11.9) | 44.9 (11.9) | — | 36.5 (11.9) | 40.1 (11.9) | — | 0.004 |
| Male, n (%) | 278 (67.5) | — | 38 (64.4) | — | 0.64 | ||
| White, n (%) | 378 (92.0) | — | 49 (86.0) | — | 0.03 | ||
| College or higher, n (%) | 189 (45.9) | 194 (47.1) | 0.46 | 28 (47.5) | 32 (54.2) | 0.16 | 0.30 |
| Full-time employed, n (%) | 290 (70.4) | 278 (67.5) | 0.17 | 30 (50.9) | 36 (61.0) | 0.18 | 0.33 |
| Income >$2,500/month, n (%) | NA | 262 (64.4) | — | NA | 29 (51.8) | — | 0.03 |
| E-cigarette–use behaviors | |||||||
| The most important reason to use an e-cigarette, n (%) | |||||||
| Less harmful to my health | 159 (38.7) | 149 (36.2) | 0.37 | 14 (23.7) | 21 (35.6) | 0.11 | 0.93 |
| To quit smoking or avoid relapsing | 126 (30.7) | 139 (33.7) | 0.27 | 18 (30.5) | 10 (17.0) | 0.03 | 0.01 |
| Mean number of devices used before the current device (SD) | 4.7 (5.7) | 10.6 (12.8) | <0.0001 | 3.4 (4.6) | 8.8 (13.9) | 0.003 | 0.18 |
| Mean amount of e-liquid used per day (in mL) (SD) | NA | 7.8 (7.1) | — | NA | 6.5 (5.6) | — | 0.23 |
| Daily e-cigarette use in the past 28 days or 30 days,c n (%) | 373 (90.5) | 387 (93.9) | 0.09 | 36 (61.0) | 39 (66.1) | 0.70 | 0.0001 |
| E-cigarette–related dependence | |||||||
| Mean PSECDI (SD) | 8.5 (3.4) | 8.4 (3.8) | 0.33 | 7.5 (3.8) | 8.0 (3.9) | 0.46 | 0.46 |
| Mean e-cigarette use times per day (SD) | 23.9 (24.7) | 21.8 (23.9) | 0.14 | 16.2 (14.6) | 15.9 (22.9) | 0.95 | 0.08 |
| Mean time to first e-cigarette use after waking (in minutes) (SD) | 44.5 (77.5) | 41.7 (73.3) | 0.54 | 64.9 (105.4) | 59.0 (109.3) | 0.75 | 0.12 |
| Awaken at night to use e-cigarette, n (%) | 29 (7.1) | 39 (9.5) | 0.10 | 6 (10.2) | 9 (15.3) | 0.32 | 0.17 |
| Mean number of nights per week awakened to use e-cigarette (SD) | 0.3 (1.2) | 0.4 (1.3) | 0.22 | 0.5 (1.5) | 0.5 (1.5) | 0.84 | 0.43 |
| Hard to quit e-cigarette, n (%) | 133 (32.4) | 83 (20.2) | <0.0001 | 20 (33.9) | 13 (22.0) | 0.14 | 0.74 |
| Have had strong cravings to use e-cigarette, n (%) | 176 (42.8) | 182 (44.3) | 0.60 | 21 (35.6) | 33 (55.9) | 0.003 | 0.09 |
| Strong urges to use e-cigarette, n (%) | 59 (14.3) | 59 (14.3) | 1.00 | 10 (17.0) | 10 (17.0) | 1.00 | 0.59 |
| Hard to keep from using e-cigarette, n (%) | 44 (10.7) | 61 (14.8) | 0.04 | 9 (15.3) | 15 (25.4) | 0.11 | 0.04 |
| Felt irritable if couldn’t use e-cigarette, n (%) | 131 (31.8) | 120 (29.1) | 0.34 | 20 (33.9) | 23 (39.0) | 0.47 | 0.12 |
| Felt nervous, restless, or anxious if couldn’t use e-cigarette, n (%) | 137 (33.3) | 130 (31.6) | 0.53 | 20 (33.9) | 26 (44.1) | 0.22 | 0.06 |
Note: Subjects with complete data on e-cigarette use and e-cigarette–related dependence were included. Boldface indicates statistical significance (p<0.05).
t-test or chi-square test p-values were used to examine the differences between exclusive e-cigarette users and poly users at follow-up.
Paired t-test or McNemar’s test p-values were used to examine changes in characteristics between baseline and follow-up.
In the baseline survey, the subjects were asked to report the number of e-cigarette use days in the past 28 days; in the follow-up survey, the subjects were asked to report the number of e-cigarette use days in the past 30 days.
NA, the questions were not comparable in the baseline survey; PSECDI, Penn State Electronic Cigarette Dependence Index.