Descriptive data at baseline
| Variables | Intervention group (N=713) | Control group (N=761) | p Value |
|---|---|---|---|
| Gender, n (%) | |||
| Male | 349 (49.5) | 352 (46.6) | 0.261 |
| Female | 356 (50.5) | 404 (53.4) | |
| Age | |||
| Mean (±SD) | 12.47 (0.79) | 12.64 (0.78) | <0.01 |
| School type, n (%) | |||
| Grammar | 281 (39.4) | 366 (48.1) | <0.01/0.046* |
| Comprehensive | 432 (60.6) | 395 (51.9) | |
| Migrant background, n (%) | 182 (27.5) | 221 (31.3) | 0.122 |
| Smoking status, n (%) | |||
| Smokers | 54 (7.6) | 41 (5.4) | 0.088 |
| Non-smokers | 659 (92.4) | 720 (94.6) | |
| Smoking behaviour of non-smokers, n (%) | |||
| Never smoked | 615 (95.1) | 683 (97.0) | |
| Stopped less than 6 months beforehand | 9 (1.4) | 12 (1.7) | 0.021 |
| Stopped more than 6 months beforehand | 23 (3.6) | 9 (1.3) | |
| Smoking behaviour of smokers, n (%) | |||
| Cigarettes (monthly-daily) | 32 (60.4) | 21 (39.6) | 0.435 |
| Daily | 8 (25.0) | 4 (19.1) | 0.613 |
| More than once per week | 2 (6.3) | 2 (9.5) | 0.659 |
| Once per week | 4 (12.5) | 3 (14.3) | 0.851 |
| Monthly | 18 (56.3) | 12 (57.1) | 0.683 |
| Water pipe smokers (monthly-daily) | 34 (58.6) | 24 (41.4) | 0.661 |
| Daily | 3 (8.8) | 0 (0) | 0.135 |
| More than once per week | 6 (17.7) | 3 (12.5) | 0.594 |
| Once per week | 5 (14.7) | 2 (8.3) | 0.463 |
| Monthly | 20 (58.8) | 19 (79.2) | 0.104 |
*p Value adjusted for class size (classes in the intervention group were systematically smaller than in the control group (mean class size=23.96 vs 25.07 in the control group; p<0.01)).