Table 1.
Results of the bivariate and multivariate logistic regression analysis at baseline and across follow-up time points 1 and 2.
| Primary and Secondary Outcomes | Intervention Group Baseline (n = 283) Follow-Up Time Point 1 (n = 273) Follow-Up Time Point 2 (n = 197) n (%) |
Control Group Baseline (n = 265) Follow-Up Time Point 1 (n = 255) Follow-Up Time Point 2 (n = 163) n (%) |
OR (95% CI) | ORa1 (95% CI) | ORa2 (95% CI) |
|---|---|---|---|---|---|
| Consumption | |||||
| Tobacco lifetime use | |||||
| Baseline | 17(6) | 18(6.8) | 0.88 [0.44–1.75] | 0.56 [0.20–1.43] | 0.38 [0.09–1.43] |
| Follow-up time point 1 | 16(6) | 19(7.5) | 0.77 [0.38–1.54] | 0.51 [0.18–1.39] | 0.35 [0.07–1.64] |
| Follow-up time point 2 | 21(10.7) | 16(9.8) | 1.10 [0.55–2.21] | 0.79 [0.26–2.28] | 1.12 [0.23–5.25] |
| Last-month alcohol use | |||||
| Baseline | 20(7.1) | 14(5.4) | 1.36 [0.67–2.80] | 1.23 [0.54–2.87] | 1.22 [0.44–3.49] |
| Follow-up time point 1 | 16(5.9) | 12(4.7) | 1.26 [0.59–2.79] | 1.07 [0.37–3.15] | 1.95 [0.45–9.23] |
| Follow-up time point 2 | 13(6.7) | 13(8) | 0.83 [0.37–1.85] | 0.10 [0.02–0.42] | 0.07 [0.01–0.66] |
| Last-month tobacco use | |||||
| Baseline | 5(1.8) | 7(2.7) | 0.66 [0.19–2.09] | NA | NA |
| Follow-up time point 1 | 5(1.8) | 8(3.1) | 0.58 [0.17–1.75] | NA | NA |
| Follow-up time point 2 | 6(3.1) | 5(3.1) | 1.00 [0.30–3.54] | NA | NA |
| Current alcohol use | |||||
| Baseline | 71(25.3) | 54(21.3) | 1.24 [0.83–1.87] | 1.04 [0.63–1.70] | 1.14 [0.63–2.07] |
| Follow-up time point 1 | 60(22.3) | 65(25.9) | 0.82 [0.55–1.23] | 0.50 [0.27–0.88] | 0.39 [0.18–0.78] |
| Follow-up time point 2 | 52(26.9) | 55(34) | 0.72 [0.45–1.13] | 0.63 [0.32–1.20] | 0.68 [0.32–1.44] |
| ◆ Psychosocial skills | |||||
| PSS1 | |||||
| Baseline | 118(42.9) | 112(43.3) | 0.98 [0.70–1.38] | 0.90 [0.59–1.38] | 0.96 [0.58–1.57] |
| Follow-up time point 1 | 142(53.4) | 144(57.1) | 0.86 [0.61–1.21] | 0.70 [0.42–1.15] | 0.72 [0.41–1.27] |
| Follow-up time point 2 | 120(62.2) | 105(66) | 0.85 [0.54–1.31] | 0.81 [0.43–1.52] | 0.88 [0.42–1.85] |
| PSS2 | |||||
| Baseline | 130(46.8) | 152(58.9) | 0.61 [0.43–0.86] | 0.60 [0.39–0.92] | 0.59 [0.36–0.96] |
| Follow-up time point 1 | 152(56.9) | 147(58.8) | 0.93 [0.65–1.31] | 1.05 [0.64–1.75] | 1.07 [0.61–1.88] |
| Follow-up time point 2 | 107(55.2) | 74(46.5) | 1.41 [0.93–2.16] | 1.34 [0.73–2.51] | 1.47 [0.72–3.09] |
| PSS3 | |||||
| Baseline | 170(61.4) | 155(60.1) | 1.06 [0.75–1.50] | 1.07 [0.70–1.64] | 1.21 [0.74–2.00] |
| Follow-up time point 1 | 178(66.9) | 150(59.5) | 1.38 [0.96–1.97] | 1.23 [0.74–2.07] | 1.23 [0.69–2.21] |
| Follow-up time point 2 | 115(59.9) | 112(71.3) | 0.60 [0.38–0.94] | 0.52 [0.27–0.99] | 0.55 [0.26–1.15] |
| PSS4 | |||||
| Baseline | 117(42.9) | 146(57.3) | 0.56 [0.40–0.79] | 0.54 [0.35–0.82] | 0.61 [0.37–1.01] |
| Follow-up time point 1 | 133(51) | 136(54) | 0.89 [0.63–1.25] | 0.88 [0.53–1.46] | 0.88 [0.48–1.61] |
| Follow-up time point 2 | 99(51.6) | 75(47.5) | 1.18 [0.77–1.80] | 1.47 [0.79–2.79] | 1.88 [0.88–4.15] |
| PSS5 | |||||
| Baseline | 136(49.3) | 155(59.6) | 0.66 [0.47–0.93] | 0.62 [0.40–0.96] | 0.67 [0.41–1.10] |
| Follow-up time point 1 | 145(55.1) | 140(56.5) | 0.95 [0.67–1.34] | 1.05 [0.62–1.80] | 1.14 [0.63–2.10] |
| Follow-up time point 2 | 106(55.5) | 103(64.8) | 0.68 [0.44–1.04] | 0.63 [0.33–1.21] | 0.64 [0.29–1.39] |
| PSS6 | |||||
| Baseline | 126(45.5) | 156(60.2) | 0.55 [0.39–0.78] | 0.56 [0.36–0.85] | 0.62 [0.38–1.01] |
| Follow-up time point 1 | 140(52.6) | 137(54.2) | 0.94 [0.67–1.33] | 0.91 [0.55–1.50] | 0.92 [0.53–1.60] |
| Follow-up time point 2 | 89(45.9) | 83(52.2) | 0.78 [0.51–1.18] | 0.88 [0.47–1.63] | 0.83 [0.40–1.70] |
| ⦿ Capacity to say "no" to a smoke for refusing a friend | |||||
| Baseline | 227(82.5) | 221(84) | 0.90 [0.57–1.41] | 0.84 [0.47–1.49] | 2.36 [0.70–8.81] |
| Follow-up time point 1 | 229(84.8) | 219(85.9) | 0.92 [0.56–1.49] | 0.66 [0.33–1.32] | 0.41 [0.13–1.28] |
| Follow-up time point 2 | 169(87.6) | 138(87.3) | 1.02 [0.54–1.92] | 0.69 [0.28–1.72] | 3.65 [0.41–4.36] |
| ⦿ Capacity to say "no" to a drink for refusing a friend | |||||
| Baseline | 203(73.6) | 206(78.6) | 0.76 [0.51–1.12] | 0.72 [0.44–1.17] | 0.49 [0.20–1.14] |
| Follow-up time point 1 | 218(81.3) | 203(79.9) | 1.10 [0.71–1.69] | 1.00 [0.53–1.88] | 1.78 [0.60–5.63] |
| Follow-up time point 2 | 157(80.9) | 137(85.6) | 0.71 [0.40–1.25] | 0.63 [0.28–1.43] | 0.70 [0.15–3.31] |
| ✪ Denormalization of tobacco or alcohol use | |||||
| Denormalization of tobacco use at home | |||||
| Baseline | 264(96.4) | 239(94.5) | 1.55 [0.68–3.65] | NA | NA |
| Follow-up time point 1 | 260(95.9) | 246(96.9) | 0.77 [0.29–1.93] | NA | NA |
| Follow-up time point 2 | 185(94.9) | 157(97.5) | 0.47 [0.13–1.44] | NA | NA |
| Denormalization of alcohol use at home | |||||
| Baseline | 225(80.6) | 214(86.6) | 0.64 [0.40–1.02] | NA | NA |
| Follow-up time point 1 | 231(85.6) | 221(87.4) | 0.86 [0.52–1.42] | NA | NA |
| Follow-up time point 2 | 165(85.1) | 143(88.8) | 0.72 [0.38–1.33] | NA | NA |
| Denormalization of tobacco use at school | |||||
| Baseline | 220(82.4) | 196(80.3) | 1.15 [0.73–1.79] | 1.13 [0.67–1.90] | 0.89 [0.43–1.83] |
| Follow-up time point 1 | 225(84) | 208(82.2) | 1.13 [0.72–1.79] | 1.71 [0.92–3.23] | 4.11 [1.60–11.33] |
| Follow-up time point 2 | 156(80) | 123(76.4) | 1.24 [0.74–2.05] | 1.41 [0.68–3.03] | 1.79 [0.54–6.24] |
| Denormalization of alcohol use at school | |||||
| Baseline | 202(74.3) | 166(69.7) | 1.25 [0.85–1.85] | 1.52 [0.95–2.46] | 1.60 [0.81–3.22] |
| Follow-up time point 1 | 179(66.8) | 187(73.9) | 0.71 [0.48–1.04] | 0.83 [0.49–1.40] | 0.44 [0.21–0.90] |
| Follow-up time point 2 | 130(67) | 104(64.6) | 1.11 [0.72–1.73] | 1.51 [0.77–3.01] | 1.22 [0.45–3.51] |
| ❖ Peer support ** | |||||
| PS1 | |||||
| Baseline | 205(74) | 200(76) | 0.90 [0.61–1.32] | 1.07 [0.66–1.74] | 1.09 [0.63–1.90] |
| Follow-up time point 1 | 179(66.5) | 185(72.8) | 0.74 [0.51–1.08] | 0.72 [0.42–1.24] | 0.79 [0.41–1.53] |
| Follow-up time point 2 | 118(61.1) | 102(63.8) | 0.89 [0.58–1.38] | 1.02 [0.54–1.99] | 0.88 [0.38–2.10] |
| PS2 | |||||
| Baseline | 191(68.7) | 189(71.9) | 0.86 [0.59–1.24] | 1.12 [0.71–1.77] | 1.21 [0.71–2.09] |
| Follow-up time point 1 | 185(68.5) | 180(70.9) | 0.89 [0.62–1.30] | 0.98 [0.58–1.68] | 0.88 [0.44–1.78] |
| Follow-up time point 2 | 108(56) | 90(56.6) | 0.97 [0.64–1.49] | 0.91 [0.49–1.73] | 0.80 [0.35–1.86] |
| PS3 | |||||
| Baseline | 223(80.5) | 212(80.9) | 0.97 [0.63–1.49] | 0.96 [0.55–1.67] | 0.91 [0.48–1.75] |
| Follow-up time point 1 | 208(77.9) | 194(76.1) | 1.11 [0.74–1.67] | 0.92 [0.51–1.64] | 0.90 [0.44–1.84] |
| Follow-up time point 2 | 138(71.1) | 121(75.6) | 0.79 [0.49–1.28] | 0.78 [0.39–1.59] | 0.84 [0.34–2.08] |
◆ “Most often”, “often” compared to “never”, “almost never” or “sometimes” (recoded 1 vs. 0). ⦿ “Very easy” or “rather easy to refuse” compared to “I do not know”, “rather difficult or very difficult to refuse” (recoded 1 vs. 0). ✪ “Disagree completely”, “rather disagree” compared to “rather agree”, “completely agree” or “neither agree nor disagree” (recoded 1 vs. 0). ❖ “Completely agree” or “rather agree” compared to “neither agree nor disagree”, “rather disagree”, “disagree completely” (recoded 1 vs. 0). NA = Not applicable. The conditions for the validity of multivariate logistic analyses were not met. The predefined adjustment variables were the following: gender, age, three social-economic variables (individual bedroom, two cars or more in the household, trip abroad during the last holiday), and a weighting variable for each school to take the magnitude of the numbers analysed for each school into account. The other potential confounding variables for baseline were the following: outings to parks and museums, no more than 2 hours spent watching screens during the week, good school results and parental alcohol consumption. The other potential confounding variables for follow-up time point 1 were the following: outings to parks and museums, under two hours watching screens in the week, good school results, talking about alcohol at home with parents, and remembering having received information in school about alcohol, tobacco or another substance. The other potential confounding variables for follow-up time point 2 were the following: having a parent using tobacco or alcohol and remembering having received information in school about alcohol, tobacco or another substance. Multivariate logistic regression model A1: adjusting on predefined adjustment variables and on other variables with an OR significantly different from 1 in the bivariate logistic regression for the follow-up time point considered. Multivariate logistic regression model A2: identical to model A1 but with the introduction of all the other primary and secondary outcomes.