Table 2

Cochrane risk of bias rating

Study, yearAdequate sequence generationAllocation concealmentBlindingIncomplete outcome data addressed?All outcomes Free of selective reportingFree of other bias
Bourbeau 200312+++++
Casas 200613,29 (Garcia-Aymerich 200722OO+O
Chandler 199015+O+
de Toledo 200614OOO+
Finkelstein 2004,23 200616OO
Johnston 200017OOO
Nguyen 200818++++
Vitacca 200919++
Whitten 200720OOO+
Wong 200521+O+O++
  • + = criterion fulfilled. – = criterion not fulfilled. O = insufficient information.