Individual results of studies included in the meta-analysis
| Initiated cigarette smoking (n) | Odds of initiating smoking | |||
| Study | E-cigarette users | Never/not current e-cigarette users | Unadjusted OR (95% CI) | Adjusted OR (95% CI) |
| Auf et al19 | * | * | * | 3.7 (3.1 to 4.5) |
| Barrington-Trimis et al15 | 184/857 | 280/4171 | 3.80 (3.10 to 4.66) | 4.57 (3.56 to 5.87) |
| Best et al16 | 74/183 | 249/1942 | 4.62 (3.34 to 6.38) | 2.42 (1.63 to 3.60) |
| Conner et al30 | 118/343 | 124/1383 | 5.32 (3.99 to 7.11) | 4.06 (2.94 to 5.60) |
| East et al38 | 11/21 | 74/902 | 12.31 (5.06 to 29.94) | 10.57 (3.33 to 33.50) |
| Hammond et al10 | 136/487 | 1313/16 831 | 4.58 (3.73 to 5.63) | 2.12 (1.68 to 2.66) |
| Leventhal et al6 | 19/222 | 71/2308 | 2.95 (1.74 to 4.99) | 1.75 (1.10 to 2.77) |
| Loukas et al9 | 114/568 | 168/1190 | 2.72 (2.10 to 3.53) | 1.36 (1.01 to 1.83) |
| Lozano et al18 | 86/216 | 950/4479 | 2.46 (1.85 to 3.26) | 1.60 (1.31 to 1.97)† |
| Miech et al7 | 4/13 | 14/213 | 6.32 (1.73 to 23.10) | 6.58 (2.04 to 57.88)† |
| Morgenstern, et al17 | 93/312 | 175/1867 | 4.11 (3.08 to 5.48) | 2.50 (1.82 to 3.54)† |
| Primack et al21 | 6/16 | 65/678 | 5.66 (1.99 to 16.07) | 8.3 (1.2 to 58.6) |
| Primack et al20 | 6/16 | 81/889 | 6.06 (2.15 to 17.10) | 6.82 (1.65 to 28.25) |
| Spindle et al11 | 45/153 | 230/2163 | 3.50 (2.41 to 5.09) | 3.37 (1.91 to 5.94) |
| Treur et al13 | 432/740 | 235/2049 | 10.83 (8.87 to 13.22) | 11.9 (3.36 to 42.11) |
| Watkins et al12 | 81/425 | 387/9923 | 5.80 (4.46 to 7.54) | 2.53 (1.80 to 3.56) |
| Wills et al14 | 42/215 | 50/926 | 4.25 (2.74 to 6.61) | 2.87 (2.03 to 4.05) |
| Overall | 1,451/4787 | 4340/52 727 | 4.59 (3.60 to 5.85) | 2.92 (2.30 to 3.71) |
*Raw data were not available or insufficient information was provided to calculate an accurate unadjusted OR.
†Estimates were provided as risk ratios and converted to ORs.