Table 3 Cohort study:

1.Did the study address a clearly focused issue?

2. Was the cohort recruited in an

3.Was the exposure accurately measured to minimise bias?acceptable way?

4.Was the outcome accurately measured to minimise bias?

5(a)Have the authors identified all important confounding factors?

5(b) Have they taken account of the confounding factors in the design and/or analysis?

6(a) Was the follow up of subjects complete enough?

6(b) Was the follow up of subjects long enough?

7.What are the results of this study?

8.How precise are the results?

9.Do you believe the results?

10.Can the results be applied to the local population?

11.Do the results of this study fit with other available evidence?

12.What are the implications of this study for practice?