Table 1

Main outcomes at 24 months

Cigarette use at baseline
E-cigarettes onlyTobacco cigarettes onlyDual use
(n=229)(n=480)(n=223)p ValueAp ValueBp ValueC
1. Cigarette use at 24 months
Tobacco cigarettes only, per cent (n)
 Continuous tobacco abstinence from baseline or cessation from tobacco smoking during follow-up*61.1 (140)23.1 (111)26.0 (58)<0.0010.4<0.001
 Tobacco smoking (continued or relapsed)38.9 (89)76.9 (369)74.0 (165)<0.0010.4<0.001
All product use (cigarettes and/or e-cigarettes), per cent (n)
 Quit using any product (either tobacco and/or e-cigarette)18.8 (43)17.5 (84)14.3 (32)0.70.30.20
 Using e-cigarettes only42.4 (97)5.6 (27)11.7 (26)<0.0010.004<0.001
 Dual use (tobacco cigarettes and e-cigarettes)8.3 (19)1.3 (6)16.6 (37)<0.001<0.0010.007
 Smoking tobacco cigarettes only30.6 (70)75.6 (363)57.4 (128)<0.001<0.001<0.001
2. Number of tobacco cigarettes
Mean number of tobacco cigarettes daily at 24 months (SD)
 Stratified by baseline group10.0 (8.4)11.2 (9.8)0.09
 Stratified by cigarette use at 24 months
  Started or continued tobacco cigarettes only0.0 (0.0)14.8 (8.1)15.8 (9.1)0.2
  Started or continued dual use only0.0 (0.0)19.0 (6.3)14.0 (9.5)0.2
(p=0.2)†(p=0.3)‡
Percentage of participants reducing tobacco cigarettes of 50% or more from baseline to 24 months
 Stratified by baseline group34.539.70.2
 Stratified by product use at 24 months
  Started or continued tobacco cigarettes only14.1 (n=51)9.4 (n=12)0.2
  Started or continued dual use only66.7 (n=4)50.0 (n=17)0.5
(p<0.001)†(p<0.001)‡
Percentage of participants who smoked ≥5 tobacco cigarettes less between baseline and 24 months
 Stratified by baseline group38.642.50.3
 Stratified by product use at 24 months
  Started or continued tobacco cigarettes only23.5 (n=85)22.1 (n=28)0.7
  Started or continued dual use only66.7 (n=4)55.9 (n=19)0.6
Mean difference in the daily number of tobacco cigarettes between 24 months and baseline (SD)
 Stratified by baseline group−4.1 (8.1)−4.0 (11.8)0.9
 Stratified by product use at 24 months
  Started or continued tobacco cigarettes only−1.6 (6.4)−0.8 (9.6)0.2
  Started or continued dual use only−5.3 (3.3)−6.5 (10.7)0.8
(p=0.2)†(p=0.003)‡
3. Self-rated health§–Mean difference between 24 months and baseline (SD)
Stratified by baseline group0.0 (1.7)0.0 (1.4)−0.1 (1.7)0.90.40.5
Stratified by product use at 24 months
 Quit using any product (either tobacco and/or e-cigarette)+0.2 (1.6)+0.3 (1.4)−0.2 (2.1)0.70.140.4
 Using e-cigarettes only+0.3 (1.4)+1.1 (1.7)+1.0 (1.6)0.0140.80.03
 Dual use (tobacco cigarettes and e-cigarettes)−0.3 (1.7)+0.3 (1.5)+0.2 (1.7)0.40.90.3
 Smoking tobacco cigarettes only−0.5 (1.9)−0.1 (1.4)−0.4 (1.4)0.0410.0390.7
4. Safety—possibly related sAEs, per cent (n)
Stratified by baseline group
 Mouth irritation6.1 (14)4.2 (20)1.8 (4)0.270.100.019
 Any sAE¶4.4 (10)2.9 (14)6.3 (14)0.30.0320.4
 Any cancer2.6 (6)1.0 (5)1.4 (3)0.100.60.4
Any sAE¶ stratified by product use at 24 months, per cent (n)
 Quit using any product (either tobacco and/or e-cigarette)4.6 (2)6.0 (5)9.4 (3)0.70.50.4
 Using e-cigarettes only2.1 (2)3.7 (1)11.5 (3)0.60.30.03
 Dual use (tobacco cigarette and e-cigarettes)5.3 (1)0.00.0 (0)0.60.16
 Smoking tobacco cigarettes only7.1 (5)2.2 (8)6.3 (8)0.0280.0250.8
  • p Value for the comparisons of the following groups at baseline: Atobacco cigarettes only versus e-cigarettes only; Btobacco cigarettes only versus dual use; Ce-cigarettes only versus dual use.

  • *Including (1) users of e-cigarettes only at baseline who quit e-cigarette use and did not start tobacco smoking; (2) smokers of tobacco cigarettes only at baseline who quit tobacco cigarette use and did not start e-cigarette use; (3) dual users at baseline who quit both tobacco smoking and e-cigarette use; (4) e-cigarette users at baseline who continued to use only e-cigarettes; (5) tobacco cigarettes smokers at baseline who quit tobacco smoking and started using e-cigarettes; (6) dual users at baseline who quit tobacco smoking and continued to use e-cigarettes only.

  • †p Value for the comparison of the tobacco-only smokers at baseline who started or continued tobacco cigarettes only versus tobacco-only smokers at baseline who started or continued dual use only.

  • ‡p Value for the comparison of the dual users at baseline who started or continued tobacco cigarettes only versus dual users at baseline who started or continued dual use only.

  • §EuroQol final item, ranging from 1 (feel very bad) to 10 (perfectly healthy).

  • ¶Mouth irritation excluded; chronic obstructive pulmonary diseases, stroke, heart failure, myocardial infarction, angina, pneumonia and any type of cancer included.

  • sAE, serious adverse event.