Table 4.

Analysis of temporal trends and relevant risk factors in smoking initiation and cessation in the four centers participating to both ISAYA (1998–2000) and GEIRD (2007–2010)

	OR of being ever smoker (95% CI)		OR of being ex-smoker
	N = 10,263		(95% CI) N = 4,468
Time			p < 0.001
ISAYA 1998-2000			1
GEIRD 2007-2010			1.32 (1.18-1.48)
	Interaction sex*time: p = 0.029
Sex	ISAYA 1998-2000	GEIRD 2007-2010	p = 0.760
Women	1	0.71 (0.65-0.79)	1
Men	1.42 (1.30-1.56)	1.19 (1.07-1.33)	0.98 (0.87-1.10)
	Interaction age*time: p < 0.001
Age	ISAYA 1998-2000	GEIRD 2007-2010	p < 0.001
20-29 years	1	0.95 (0.83-1.08)	1
30-39 years	1.26 (1.14-1.40)	1.00 (0.88-1.12)	1.93 (1.67-2.23)
40-47 years	1.84 (1.62-2.09)	1.09 (0.95-1.24)	2.47 (2.10-2.89)
	Interaction occupation*time: p = 0.047
Occupation	ISAYA 1998-2000	GEIRD 2007-2010	p < 0.001
Clerk	1	0.74 (0.66-0.83)	1
Housewife	1.25 (1.06-1.46)	0.75 (0.59-0.94)	1.07 (0.88-1.31)
Manager	1.01 (0.73-1.41)	0.68 (0.44-1.04)	0.95 (0.64-1.40)
Businessman	1.55 (1.19-2.01)	1.05 (0.75-1.46)	0.87 (0.66-1.16)
Free-lancer	1.14 (0.98-1.32)	0.78 (0.65-0.94)	0.76 (0.64-0.91)
Workman	1.49 (1.31-1.70)	1.27 (1.08-1.49)	0.75 (0.64-0.87)
Unemployed	1.11 (0.92-1.33)	1.24 (0.98-1.57)	0.61 (0.48-0.78)
Student	0.67 (0.56-0.79)	0.60 (0.49-0.73)	0.70 (0.54-0.91)
Other job	1.47 (1.21-1.79)	1.13 (0.83-1.54)	0.96 (0.76-1.22)

Odds Ratios (ORs) and 95% confidence intervals (CI) were obtained by logistic regression models, comprising time (ISAYA/GEIRD), centre, sex, age, occupation, season of response, percentile rank of cumulative response and type of contact.

The column dealing with the trend of smoking initiation (being ever smoker) was split in two as there were significant interactions between time and the main predictors (sex, age, occupation). The column dealing with smoking cessation (being ex-smoker) was not split as no significant interaction emerged.