Table 2 Quality assessment for included non-RCT studies

Representativeness of the exposed cohort

*

*

*

*

*

*

*

*

Selection of the non-exposed cohort

*

*

*

*

*

*

*

*

Ascertainment of exposure

*

*

*

*

*

*

*

*

Demonstration that outcome of interest was not present at start of study

/

/

/

/

/

/

/

/

Comparability of cohorts on the basis of the design or analysis

**

**

**

**

**

/

**

**

Assessment of outcome

*

*

*

*

*

*

*

*

Was follow-up long enough for outcomes to occur

*

*

*

*

*

*

*

*

Adequacy of follow-up of cohorts

*

*

*

*

*

*

*

*

Summary quality score

8

8

8

8

8

6

8

8