TABLE 2

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 CharacteristicWave 1Wave 2
Use <10 dUse at Least 10 d per moPUse <10 dUse at Least 10 d per moP
E-cigarette used most of the time is rechargeable
 χ2 test, n (%)208 (71.8)70 (87.3).006203 (77.5)123 (90.9).006
 LR, aOR (95% CI)Ref2.7 (1.4–5.3)Ref2.7 (1.5–5.1)
E-cigarette used most of the time uses cartridges
 χ2 test, n (%)200 (35.5)70 (28.5)ns203 (34.4)121 (23.0).049
 LR, aOR (95% CI)Ref0.7 (0.4–1.3)Ref0.6 (0.4–1.1)
E-cigarette used most of the time can be refilled
 χ2 test, n (%)206 (61.6)70 (79.6).005206 (79.7)123 (91.4).012
 LR, aOR (95% CI)Ref2.0 (1.2–3.5)Ref2.7 (1.6–4.6)
E-cigarette used most of the time is a tank system
 χ2 test, n (%)n/an/an/a205 (38.8)123 (58.3).001
 LR, aOR (95% CI)n/an/aRef1.9 (1.2–3.0)
E-cigarette used most of the time has modifiable voltage
 χ2 test, n (%)n/an/an/a205 (29.1)123 (50.1).001
 LR, aOR (95% CI)n/an/aRef2.5 (1.6–3.9)
E-cigarette used most of the time has been modified at all
 χ2 test, n (%)n/an/an/a204 (17.5)123 (36.7)<.001
 LR, aOR (95% CI)n/an/aRef2.8 (1.7–4.6)
Used a flavored e-cigarette in the past 30 d
 χ2 test, n (%)330 (84.6)83 (88.2)ns245 (88.3)122 (87.8)ns
 LR, aOR (95% CI)Ref0.8 (0.4–1.5)Ref1.1 (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.