Methodological quality assessment
The risk of bias in the selected studies was assessed using an adaptation of the Cochrane Collaboration’s tool for assessing the risk of bias (ROB).10 The criteria involved assessing studies for selection bias caused by random sequence generation and allocation concealment; performance bias caused by blinding of participants and personnel; detection bias caused by blinding of outcome assessment; attrition bias caused by incomplete outcome data; and reporting bias caused by selective outcome reporting. We assigned a judgment related to risk of bias by answering a prespecified question about the adequacy of the study in relation to the entry. A judgment of ”green” indicated a low risk of bias, ”red” indicated a high risk of bias, and ”yellow” indicated an unclear or unknown risk of bias. The methodological quality of the included studies was independently assessed by two researchers (J.H.S. and D.H.L.). Disagreements were resolved by discussion.