Table 7 Quality appraisal OS

Reference

Study addressed a clearly focused issue

Authors used an appropriate method to answer their question

Cases/cohort were/was recruited in an acceptable way

Controls were selected in an acceptable way

The exposure was accurately measured to minimize bias

The outcome was accurately measured to minimize bias

The authors identified all important confounding factors

The follow up of subjects was complete enough

The follow up of subjects was long enough

Results can be applied to the local population