Association of Frequency of Use and Characteristics of the E-cigarette Used Most of the Time (χ2 Test for Independence and Logistic Regression Analyses)
| E-cigarette Characteristic . | Wave 1 . | . | Wave 2 . | . | ||
|---|---|---|---|---|---|---|
| Use <10 d . | Use at Least 10 d per mo . | P . | Use <10 d . | Use at Least 10 d per mo . | P . | |
| E-cigarette used most of the time is rechargeable | ||||||
| χ2 test, n (%) | 208 (71.8) | 70 (87.3) | .006 | 203 (77.5) | 123 (90.9) | .006 |
| LR, aOR (95% CI) | Ref | 2.7 (1.4–5.3) | Ref | 2.7 (1.5–5.1) | ||
| E-cigarette used most of the time uses cartridges | ||||||
| χ2 test, n (%) | 200 (35.5) | 70 (28.5) | ns | 203 (34.4) | 121 (23.0) | .049 |
| LR, aOR (95% CI) | Ref | 0.7 (0.4–1.3) | Ref | 0.6 (0.4–1.1) | ||
| E-cigarette used most of the time can be refilled | ||||||
| χ2 test, n (%) | 206 (61.6) | 70 (79.6) | .005 | 206 (79.7) | 123 (91.4) | .012 |
| LR, aOR (95% CI) | Ref | 2.0 (1.2–3.5) | Ref | 2.7 (1.6–4.6) | ||
| E-cigarette used most of the time is a tank system | ||||||
| χ2 test, n (%) | n/a | n/a | n/a | 205 (38.8) | 123 (58.3) | .001 |
| LR, aOR (95% CI) | n/a | n/a | Ref | 1.9 (1.2–3.0) | ||
| E-cigarette used most of the time has modifiable voltage | ||||||
| χ2 test, n (%) | n/a | n/a | n/a | 205 (29.1) | 123 (50.1) | .001 |
| LR, aOR (95% CI) | n/a | n/a | Ref | 2.5 (1.6–3.9) | ||
| E-cigarette used most of the time has been modified at all | ||||||
| χ2 test, n (%) | n/a | n/a | n/a | 204 (17.5) | 123 (36.7) | <.001 |
| LR, aOR (95% CI) | n/a | n/a | Ref | 2.8 (1.7–4.6) | ||
| Used a flavored e-cigarette in the past 30 d | ||||||
| χ2 test, n (%) | 330 (84.6) | 83 (88.2) | ns | 245 (88.3) | 122 (87.8) | ns |
| LR, aOR (95% CI) | Ref | 0.8 (0.4–1.5) | Ref | 1.1 (0.6–2.1) | ||
| E-cigarette Characteristic . | Wave 1 . | . | Wave 2 . | . | ||
|---|---|---|---|---|---|---|
| Use <10 d . | Use at Least 10 d per mo . | P . | Use <10 d . | Use at Least 10 d per mo . | P . | |
| E-cigarette used most of the time is rechargeable | ||||||
| χ2 test, n (%) | 208 (71.8) | 70 (87.3) | .006 | 203 (77.5) | 123 (90.9) | .006 |
| LR, aOR (95% CI) | Ref | 2.7 (1.4–5.3) | Ref | 2.7 (1.5–5.1) | ||
| E-cigarette used most of the time uses cartridges | ||||||
| χ2 test, n (%) | 200 (35.5) | 70 (28.5) | ns | 203 (34.4) | 121 (23.0) | .049 |
| LR, aOR (95% CI) | Ref | 0.7 (0.4–1.3) | Ref | 0.6 (0.4–1.1) | ||
| E-cigarette used most of the time can be refilled | ||||||
| χ2 test, n (%) | 206 (61.6) | 70 (79.6) | .005 | 206 (79.7) | 123 (91.4) | .012 |
| LR, aOR (95% CI) | Ref | 2.0 (1.2–3.5) | Ref | 2.7 (1.6–4.6) | ||
| E-cigarette used most of the time is a tank system | ||||||
| χ2 test, n (%) | n/a | n/a | n/a | 205 (38.8) | 123 (58.3) | .001 |
| LR, aOR (95% CI) | n/a | n/a | Ref | 1.9 (1.2–3.0) | ||
| E-cigarette used most of the time has modifiable voltage | ||||||
| χ2 test, n (%) | n/a | n/a | n/a | 205 (29.1) | 123 (50.1) | .001 |
| LR, aOR (95% CI) | n/a | n/a | Ref | 2.5 (1.6–3.9) | ||
| E-cigarette used most of the time has been modified at all | ||||||
| χ2 test, n (%) | n/a | n/a | n/a | 204 (17.5) | 123 (36.7) | <.001 |
| LR, aOR (95% CI) | n/a | n/a | Ref | 2.8 (1.7–4.6) | ||
| Used a flavored e-cigarette in the past 30 d | ||||||
| χ2 test, n (%) | 330 (84.6) | 83 (88.2) | ns | 245 (88.3) | 122 (87.8) | ns |
| LR, aOR (95% CI) | Ref | 0.8 (0.4–1.5) | Ref | 1.1 (0.6–2.1) | ||
aOR was adjusted for smoking status, age, sex, and race. aOR, adjusted odds ratio; CI, confidence interval; LR, logistic regression; ns, not significant; n/a, not applicable.