Table 1 Methodological quality scores for the included articles
Quality criteriaHeijbel, 200625Schroer, 200526Gjesdal, 200427Janssen, 200328Van der Giezen, 200029
Study population+++++
Follow-up response+??++
Information completers versus_?+_
those lost to follow-up
Main outcome measure+++++
Frequencies, risk factors++___
Quality score65465
  • +, Method description in text meets criterion; ?, no method description about this criterion is mentioned in the text, so it is not clear if the method meets the criterion; –, method description in text does not meet criterion.