Schinke 1994.

Methods	Country: United States of America Design: Randomized controlled trial Objective/s: To investigate an intervention outcome study of a prevention strategy developed for Native American youth at risk for adopting habitual and lifelong habits of tobacco use Study Site: Fourth and fifth grade youths from both reservation sites and tribal schools; n = 27 tribal or public schools on 10 reservations in 5 states across western United States Programme name: Not reported Methods of analysis: Chi2 tests used to detect differences between genders, ANOVA, no correction for intra‐class correlation. Scheffe post‐hoc multiple comparison tests Cluster adjustment made: No
Participants	Eligible for study (n‐value): Clusters: n =10 reservations in North and South Dakota; n = 27 tribal and public schools Recruited: Clusters: n =10 reservations in North and South Dakota; n = 27 tribal and public schools Individuals: n =1396 Completed: 18% attrition; Total population only ‐ Individuals: T1 n = 1396; T2 n = 1374; T3 n = 1329; T4 n = 1268; T5 n = 1199 Age: Mean 10 years at baseline Gender: At follow‐up 49% female Ethnicity: Native American Socio‐economic status: Not reported Recruitment means: Reservation sites and tribal schools
Interventions	Theoretical basis: Life skills and social influence models of prevention Intervention description/s: Skills‐only: Fifteen classroom group interventions and booster sessions six months after initial intervention; Interventions included material on bicultural competence, tobacco use knowledge, cognitive and behavioural techniques for problem solving, communication and resistance and stress and coping; Interactive classroom work was used with participation in rehearsals of techniques to avoid tobacco use Skills‐community: As above plus an annual intervention designed to involve the community including various activities in which students modelled the skills they had learned in classrooms to their parents and other community members; Publications and posters were produced to further educate parents and other community members about the nature and purpose of the intervention; Media was used to enhance participation using traditional Native American legends and puppets to initiate and enhance classroom discussion; Group leaders and group discussions were employed to encourage students to discuss their learning experiences at home and in the community Control description/s: Not described, assumed no intervention control Duration of intervention: Fifteen x 50 minute classroom lessons plus booster sessions at six months Intervention delivered by: Health professionals who had participated in week‐long training workshops run by study investigators
Outcomes	Method of outcome collection: Questionnaires (no further details) Pre‐specified outcome data: Demographics, use rates, intentions to use smoked and smokeless tobacco, plus numerous other structural, environmental, social and psychological factors likely to predict future risk for use of tobacco substances Validation: Thiocyanate and cotinine were administered to every client at each measurement occasion, only a small proportion analysed; Correlation only 0.53 but no information about levels of misreporting Follow‐up period: Three years post‐intervention (or 3.5‐years post recruitment) Number of follow‐up periods reported: Four after baseline: T1 baseline/ T2 six months/ T3 one year/ T4 two years/ T5 three years Process measures: Not reported Definition of tobacco use: Weekly: number of cigarettes smoked during the 7 days prior to test administration; Monthly: month prior to test administration; Yearly: Used during the year subsequent to initial follow‐up
Notes
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Low risk	Randomized using a random numbers table on a spreadsheet ‐ data obtained from contact with authors
Allocation concealment (selection bias)	High risk	Allocation was not concealed
Blinding of participants and personnel (performance bias) All outcomes	High risk	Due to the nature of the intervention it is not possible to blind participants
Blinding of outcome assessment (detection bias) All outcomes	Unclear risk	No mention of attempted blinding for assessors
Incomplete outcome data (attrition bias) All outcomes	Unclear risk	Insufficient information to permit judgement of yes or no; Cotinine measurements collected but not all were tested, however those that were tested were not reported in this paper; Subject survey missing data were removed from analysis
Selective reporting (reporting bias)	Unclear risk	'Post‐hoc' analysis for self‐reported substance use was conducted to assess differences by study arm using the Scheffe multiple comparison test; It is unclear if this method of testing was pre‐determined at the protocol stage
Imbalance of outcome measures at baseline	Low risk	Differences were present between conditions for smokeless tobacco use with control subjects reporting ever use and used in the past month significantly more than those in the skills‐only condition, however ANOVA analysis performed; Students did not differ among the 3‐arms for ‘subject’s use of cigarettes’
Comparability of intervention and control group characteristics at baseline	Low risk	Slight but significant demographic differences were observed between the skills‐only condition for both age and gender which were higher compared to the other conditions; Analysis of covariance occurred for imbalances
Protection against contamination	Unclear risk	Authors state the likelihood of contamination between and among intervention and control arms is small; However this can not be ruled out
Selective recruitment of participants	Unclear risk	Eligible individuals prior to recruitment not stated; Methods of recruitment not stated