Table 2.

Prospective associations between dual use of e-cigarettes and tobacco at baseline and quit attempts, successful cessation among those who made a quit attempt, and overall quits at 12-month follow-up, adjusting for covariates measured at baseline.

		Prevalence, % (n)			OR [95% CI] p		ORadj [95% CI]1p
		Exclusive smokers (1)	Dual users of NRT and tobacco (2)	Dual users of e-cigarettes and tobacco (3)	(3) vs. (1)	(3) vs. (2)	(3) vs. (1)	(3) vs. (2)
Dual use for any reason, n		1089	117	292
	Past-year quit attempts	34.5 (3 7 6)	61.5 (72)	47.9 (1 4 0)	1.75 [1.35–2.27]<0.001*	0.58 [0.37–0.89] 0.013*	1.27 [0.95–1.69] 0.108	0.61 [0.38–0.98] 0.039*
	Quit success2	35.0 (1 3 0)	25.7 (18)	29.5 (41)	0.78 [0.51–1.18] 0.238	1.21 [0.63–2.31] 0.567	0.89 [0.56–1.41] 0.621	1.16 [0.58–2.34] 0.678
	Overall quits	13.3 (1 4 5)	20.5 (24)	18.2 (53)	1.44 [1.02–2.04] 0.037*	0.86 [0.50–1.47] 0.581	1.31 [0.90–1.89] 0.161	0.91 [0.52–1.61] 0.752
Dual use for harm reduction, n		4133	114	280
	Past-year quit attempts	44.6 (1 8 4)	60.5 (69)	47.9 (1 3 4)	1.14 [0.84–1.55] 0.392	0.60 [0.38–0.93] 0.023*	1.08 [0.78–2.84] 0.637	0.61 [0.37–0.98] 0.042*
	Quit success2	38.5 (70)	27.9 (19)	28.6 (38)	0.64 [0.40–1.04] 0.069	1.03 [0.54–1.98] 0.925	0.72 [0.42–1.23] 0.225	1.12 [0.55–2.31] 0.751
	Overall quits	18.6 (77)	21.1 (24)	17.5 (49)	0.93 [0.62–1.38] 0.702	0.80 [0.46–1.37] 0.411	0.98 [0.64–1.49] 0.916	0.83 [0.46–1.48] 0.520

¹Adjusted for age, sex, ethnicity, social grade, number of cigarettes smoked per day, strength of urges to smoke, motivation to stop smoking, and past-year quit attempts at baseline, and year and quarter of survey. Models relating to the success of quit attempts also controlled for time since the quit attempt began and whether the quit attempt was abrupt or gradual, measured at 12-month follow-up.

²Among those who reported at least one quit attempt in the past 12 months.

³Exclusive smokers who reported trying to cut down.

^*p < 0.05.