Subgroups Among Smokers in Preparation: A Cluster Analysis Using the I-Change Model

Figures & data

Figure 1. Identified cluster profiles for the four-cluster solution.

Figure 2. Identified cluster profiles for the four-cluster solution in three random subsamples.

Table 1. Baseline sample characteristics (N = 753).

Variables
Gender (% male; n)	49.1; 370
Age (Mean; SD)	51.7; 12.2
Educational level (% medium; n)	46.2; 348
Cigarette dependence (Mean; SD)	5.0; 2.5
Perceived pros of quitting (Mean; SD)	3.7; .7
Perceived cons of quitting (Mean; SD)	2.5; .8
Quitting self-efficacy (Mean; SD)	3.4; .7
Number of previous quit attempts (Mean; SD)	5.9; 20.0
Experimental condition (% intervention, n)	51.1; 385

Table 2. Cross-sectional comparisons of the four clusters with respect to cognitive variables (z-scores) and other variables.

	1. Classic Preparer (n = 253)	2. Unprepared Preparer (n = 120)	3. Disengaged Preparer (n = 180)	4. Progressing Preparer (n = 187)	χ^2 / F	V / ω	Tukey HSD pattern
Perceived pros^a	.88, .55	−.16, .87	−1.02, .72	−.08, .69	273.54^***	.72	1 > 2, 4 > 3^***
Perceived cons^a	.22, .81	1.27, .88	−.33, .59	−.80, .61	218.40^***	.68	2 > 1 > 3 > 4^***
Self-efficacy^a	.02, .83	−1.24, .70	−.21, .54	.97, .68	241.67^***	.70	4 > 1 > 3 > 2^***
Male gender^b	43.1, 109	35.8, 43	53.3, 96	61.0, 11.4	23.93^***	.18	.
Age^a	51.9, 11.4	53.2, 11.6	52.2, 13.3	50.3, 12.1	1.60	.05	ns
Educational level					12.68^*	.09	.
Low^b	21.3, 54	28.3, 34	20.0, 36	14.4, 27
Medium^b	45.1, 114	44.2, 53	50.0, 90	44.9, 84
High^b	33.6, 85	27.5, 33	30.0, 54	40.6, 76
Cigarette dependence^a	5.0, 2.4	6.3, 2.2	5.1, 2.4	4.0, 2.4	23.37^***	.29	2 > 1, 3 > 4^***
Previous quit attempts^a	5.1, 7.8	6.8, 16.8	5.7, 19.1	6.8, 31.7	0.35	.05	ns

^a = Mean, SD;

^b = %, N; V = Cramer's V; ω = Omega;

^* p < .05;

^*** p < .001; ns = non-significant;. = not applicable.

Table 3. Logistic and multinomial regression analyses with smoking abstinence and stage transition at six-week follow-up as dependent variables.

	Smoking abstinence (n = 306)				Negative stage transition (n = 24)^1				Positive stage transition (n = 201)^1
			95% CI				95% CI			95% CI
Six-week follow-up	R²	OR	Lower	Upper	R²	OR	Lower	Upper	OR	Lower	Upper
Reference category: Classic Preparer
	.087				.13
Unprepared Preparer		.67	.27	1.69		1.09	.30	3.88	.54	.23	1.31
Disengaged Preparer		.65	.31	1.39		.90	.25	3.23	1.28	.59	2.76
Progressing Preparer		1.06	.54	2.07		.45	.10	1.95	1.05	.51	2.14
Condition^2		2.27^**	1.29	3.97		.44	.16	1.19	1.18	.68	2.07
Cigarette dependence		.97	.86	1.09		1.06	.86	1.31	.97	.86	1.09
Low education level^3		2.27^*	1.04	4.94		2.45	.59	10.14	2.62	.95	7.25
Medium education level^3		.85	.46	1.57		.56	.19	1.70	.67	.37	1.21
Gender^4		.65	.38	1.12		1.19	.42	3.38	.51^*	.29	.91
Reference category: Progressing Preparer
Classic Preparer		.95	.48	1.86		2.24	.51	9.75	.95	.47	1.95
Unprepared Preparer		.63	.24	1.71		2.43	.45	13.17	.52	.20	1.35
Disengaged Preparer		.62	.28	1.38		2.00	.39	10.23	1.22	.54	2.74
Condition^2		2.27^**	1.29	3.97		.44	.16	1.19	1.18	.68	2.07
Cigarette dependence		.97	.86	1.09		1.06	.86	1.31	.97	.86	1.09
Low education level^3		2.27^*	1.04	4.94		2.45	.59	10.14	2.62	.95	7.25
Medium education level^3		.85	.46	1.57		.56	.19	1.70	.67	.37	1.21
Gender^4		.65	.38	1.12		1.19	.42	3.38	.51^*	.29	.91
Reference category: Unprepared Preparer
Classic Preparer		1.49	.59	3.76		.92	.26	3.30	1.84	.77	4.44
Progressing Preparer		1.58	.58	4.26		.41	.08	2.24	1.93	.74	5.04
Disengaged Preparer		.98	.35	2.72		.83	.19	3.63	2.36	.89	6.24
Condition^2		2.27^**	1.29	3.97		.44	.16	1.19	1.18	.68	2.07
Cigarette dependence		.97	.86	1.09		1.06	.86	1.31	.97	.86	1.09
Low education level^3		2.27^*	1.04	4.94		2.45	.59	10.14	2.62	.95	7.25
Medium education level^3		.85	.46	1.57		.56	.19	1.70	.67	.37	1.21
Gender^4		.65	.38	1.12		1.19	.42	3.38	.51^*	.29	.91

¹ Reference category: no stage transition (n = 75);

² Reference category: standard care;

³ Reference category: high education level;

⁴ Reference category: male;

^* p < .05.

Table 4. Logistic and multinomial regression analyses with smoking abstinence and stage transition at six-month follow-up as dependent variables.

	Smoking abstinence (n = 206)					Negative stage transition (n = 31)^1				Positive stage transition (n = 98)^1
			95% CI					95% CI			95% CI
Six-month follow-up	R²	OR	Lower		Upper	R²	OR	Lower	Upper	OR	Lower	Upper
Reference category: Classic Preparer
	.096					.10
Unprepared Preparer		.64		.15	2.63		2.49	.54	11.44	.71	.23	2.19
Disengaged Preparer		.58		.18	1.84		1.73	.52	5.71	.44	.19	1.03
Progressing Preparer		2.05		.76	5.55		1.33	.36	4.89	.58	.24	1.37
Condition^2		1.04		.46	2.35		.64	.26	1.60	1.20	.61	2.33
Cigarette dependence		1.07		.89	1.28		.86	.69	1.05	.91	.78	1.05
Low education level^3		4.19^*		1.41	12.50		2.30	.61	8.70	1.05	.39	2.85
Medium education level^3		1.24		.47	3.30		2.02	.71	5.75	1.17	.57	2.43
Gender^4		1.08		.48	2.40		1.07	.43	2.63	1.18	.61	2.29
Reference category: Progressing Preparer
Classic Preparer		.49	.18		1.32		.75	.21	2.77	1.73	.73	4.10
Unprepared Preparer		.31	.07		1.37		1.87	.41	8.61	1.23	.38	4.00
Disengaged Preparer		.28^*	.09		.95		1.30	.41	4.12	.76	.31	1.86
Condition^2		1.04	.46		2.35		.64	.26	1.60	1.20	.61	2.33
Cigarette dependence		1.07	.89		1.28		.86	.69	1.05	.91	.78	1.05
Low education level^3		4.19^*	1.41		12.50		2.30	.61	8.70	1.05	.39	2.85
Medium education level^3		1.24	.47		3.30		2.02	.71	5.75	1.17	.57	2.43
Gender^4		1.08	.48		2.40		1.07	.43	2.63	1.18	.61	2.29
Reference category: Unprepared Preparer
Classic Preparer		1.57	.38		6.51		.40	.09	1.85	1.41	.46	4.34
Progressing Preparer		3.22	.73		14.21		.53	.12	2.45	.81	.25	2.64
Disengaged Preparer		.91	.19		4.39		.69	.17	2.86	.62	.19	1.99
Condition^2		1.04	.46		2.35		.64	.26	1.60	1.20	.61	2.33
Cigarette dependence		1.07	.89		1.28		.86	.69	1.05	.91	.78	1.05
Low education level^3		4.19^*	1.41		12.50		2.30	.61	8.70	1.05	.39	2.85
Medium education level^3		1.24	.47		3.30		2.02	.71	5.75	1.17	.57	2.43
Gender^4		1.08	.48		2.40		1.07	.43	2.63	1.18	.61	2.29

¹ Reference category: no stage transition (n = 62);

² Reference category: standard care;

³ Reference category: high education level;

⁴ Reference category: male;

^* p < .05.

Table A1. Cross-sectional comparisons of the three clusters with respect to cognitive variables (z-scores).

Total sample	1. Classic Preparer (n = 253)	2. Unprepared Preparer (n = 120)	3. Disengaged (n = 367)	Tukey HSD pattern
Pros^a	.88; .55	−.16; .87	−.54; .85	1 > 2 > 3^***
Cons^a	.22; .81	1.27; .88	−.57; .64	2 > 1 > 3^***
Self-efficacy^a	.21; .83	−1.24; .70	.39; .85	3 > 1 > 2^***

^a = Mean, SD;

^*p < .05;

^*** p < .001.

Figure A1. Cluster profiles for the three-cluster solution.

Figure A2. Cluster profiles for the three-cluster solution in three random subsamples.