Study design, methods and key outcomes of included studies
| Author and year | Cohort name, type and location | Final sample size | Follow-up rate | Data collection points for age of first drink (AFD) and outcomes | Alcohol-related outcomes measured | Confounders included in multivariable analysis | Key outcome data: (OR, 95% CIs given in brackets where available) (AFD=age of first drink) |
|---|---|---|---|---|---|---|---|
| Pedersen and Skrondal 199818 | School-based cohort (Oslo, Norway) | 522 | 89% | AFD data collected at: T1 (12–15 years) T2 (13–16 years) T3 (14–17 years) T4 (15–18 years) T5 (18–21 years) Outcomes measured at T5 (18–21 years) | Alcohol consumption (past month) Problem drinking (past year) as measured by the Rutgers Alcohol Problem Index (RAPI) | Parental social norms. Parental smoking and alcohol use. Parental alcohol problems. Friends’ social norms. Friends’ alcohol and tobacco use. | Alcohol debut age vs alcohol consumption Structural equation coefficient=−3.465 (p<0.0001). Result roughly equates to a 10% delay in alcohol debut resulting in a 35% reduction in alcohol consumption Alcohol debut age vs alcohol problem index Structural equation coefficient=−13.828 (p<0.0001). |
| Warner and White 200319 | Rutgers Health and Human Development Project. Community based cohort (USA) | 447 | 83% | AFD data collected at: T1 (12 years) T2 (15 years) T3 (18 years) Outcomes measured at T1–T3 and: T4 (25 years) T5 (30–31 years) | Lifetime incidence of problem drinking (dependence or abuse) | Gender. Religion. Parental status. Setting of first drink. Pleasantness of first drink experience. Drunkenness at first drink experience. Family history of alcoholism. Family and friends’ alcohol use. Strength of parental relationship. Delinquency. Academic performance. Presence of psychiatric symptoms. | Lifetime problem drinking AFD <11 years of age at a family gathering vs AFD 11 years+ at a family gathering: OR=2.39 (1.10–5.20) p<0.05 AFD<11 years outside a family gathering vs AFD 11 years+ at a family gathering: OR=5.75 (1.53–21.54) p<0.01 Final multivariable model: Regression coefficient for effect of AFD on problem drinking=−0.0631, p>0.05 |
| Rossow and Kuntsche 201322 | The Young in Norway Longitudinal Study. National school-based cohort study (Norway) | 1311 | 82.4% | T1 (13–14 years) Outcome data collected at T2 (26–27 years) | Heavy drinking (Drinking to intoxication 10 or more times in last 12 months) Harmful alcohol use (AUDIT score=8 or more) | Gender Conduct problems at T1. | Model 1: Controlling for gender only OR for frequent intoxication: early AFD (<13/14 years)=1.5 (1.2–1.9) vs late AFD. p<0.01 OR for harmful alcohol use (AUDIT score 8 or more): early AFD=1.6 (1.3–2.1) vs late AFD p<0.01 Model 2: Additional adjustment for conduct problems: OR for frequent intoxication: early AFD (<13/14 years)=1.2 (0.9–1.6) vs late AFD. p>0.05 OR for harmful alcohol use (AUDIT score 8 or more): early AFD=1.2 (0.9–1.6) vs late AFD p>0.05 |
| Guttmannova et al 201120 | Seattle Social Development Project. School-based cohort (Seattle, USA) | 808 | 92% | AFD data collected at: T1 (10–11 years) T2 (11–12 years) T3 (12–13 years) T4 (13–14 years) T5 (14–15 years) T6 (15–16 years) T7 (17–18 years) T8 (21 years) T9 (24 years) T10 (27 years) Outcome data collected at T8, T9, T10 and at T11 (30 years ) and T12 (33 years) | Alcohol misuse in the year prior to any follow-up point. Lifetime incidence of alcohol misuse. Alcohol dependence in the year prior to any follow-up point. Alcohol dependence at multiple follow-up waves (chronicity of alcohol dependence). | Gender. Ethnicity. Childhood poverty. Frequency of substance use during adolescence (including tobacco, marijuana and other illicit drug use). | Alcohol misuse at any follow up point AFD less than 11 years: OR=0.96 (p>0.05) AFD 11–14 years: reference AFD 15–17 years: OR=1.40 (p>0.05) AFD 18–20 years: OR=0.64 (p>0.05) Chronicity of alcohol misuse AFD less than 11 years: OR=1.20 (p>0.05) AFD 11–14 years: reference AFD 15–17 years: OR=1.13 (p>0.05) AFD 18–20 years: OR=0.77 (p>0.05) Alcohol dependence at any follow up point AFD less than 11 years: OR=1.49 (p>0.05) AFD 11–14 years: reference AFD 15–17 years: OR=1.16 (p>0.05) AFD 18–20 years: OR=0.35 (p>0.05) Chronicity of alcohol dependence AFD less than 11 years: OR=1.68 (p<0.05) AFD 11–14 years: reference AFD 15–17 years: OR=1.04 (p>0.05) AFD 18–20 years: (p>0.05) |
| Guttmannova et al 201221 | Seattle Social Development Project. School-based cohort (Seattle, USA) | 706 | 100% | AFD data collected at: T1 (10–11 years) T2 (11–12 years) T3 (12–13 years) T4 (13–14 years) T5 (14–15 years) T6 (15–16 years) T7 (17–18 years) T8 (21 years) T9 (24 years) Outcome data collected at T8, T9, T10 (27 years), T11 (30 years) and T12 (33 years) | Alcohol dependence at multiple follow-up waves (chronicity of alcohol dependence). | Gender, ethnicity, poverty, parental drinking, family bonding, family management. 4 multivariable models tested, all including above covariates and also:
| Bivariate association between early AFD (<11 years) and chronicity of alcohol dependence: regression coefficient β=0.44 (p<0.05). Magnitude of association remains largely unaffected in 4 separate regression models, aiming to test hypotheses that association is attributable to other predictive factors. Model 1: Peer factors β=0.53 (p<0.01) Model 2: School factors β=0.46 (p<0.05) Model 3: Behavioural factors β=0.45 (p<0.05) Model 4: Substance misuse factors β=0.46 (p<0.05) |
AFD, age of first drinking.