Table 2:

Assessment of risk of bias, based on the Risk of Bias in Nonrandomized Studies of Interventions tool13

ArticleType of biasConflict of interestFunding*
ConfoundingSelection of participantsClassification of interventionsDeviations from interventionsMissing dataMeasurement of outcomesSelection of resultsOverall
Leach et al. (2004)12SeriousModerateLowLowLowModerateLowSeriousUnclearUnclear
Bichel et al. (2009)14SeriousLowLowModerateModerateLowLowSeriousUnclearLow
Bungard et al. (2009)15SeriousLowLowModerateLowLowLowSeriousUnclearLow
Macleod et al. (2009)10SeriousCriticalLowLowModerateLowLowCriticalUnclearUnclear
Van den Heuvel et al. (2012)16CriticalLowLowModerateModerateModerateModerateCriticalHighUnclear
Schachter et al. (2013)17SeriousModerateLowModerateModerateLowLowSeriousUnclearLow
Clark (2015)11SeriousLowLowModerateModerateLowLowSeriousUnclearUnclear
Hazlewood et al. (2016)6SeriousLowLowModerateSeriousLowLowSeriousUnclearLow
Wittmeier et al. (2016)18SeriousLowLowModerateModerateLowModerateSeriousLowLow
Goodsall et al. (2017)19SeriousModerateLowModerateModerateLowLowSeriousUnclearUnclear
  • * High risk = industry sponsorship, low-risk = non-industry sponsorship, unclear risk = not reported.

  • The quality assessment for the study by Clark11 was based on a conference abstract of the study, given that no peer-reviewed full-text article was publicly available.