Relationship between alcohol and primary headaches: a systematic review and meta-analysis

Table 3 Assessment of risk of bias for cohort studies according to the Joanna Briggs Institute (JBI) checklist

Study authors	Q1	Q2	Q3	Q4	Q5	Q6	Q7	Q8	Q9	Q10	Q11	Overall risk of bias assessment
Schramm S et al. [45]	Yes	Yes	No	Yes	Yes	No	Yes	Yes	Yes	No	Yes	Moderate
Hagen K et al. [36]	Yes	Yes	No	Yes	Yes	No	Yes	Yes	Yes	No	Yes	Moderate
Schramm SH et al. [52]	Yes	Yes	No	Unclear	Yes	No	No	Yes	Yes	No	Yes	High
Yoon MS et al. [55]	Yes	Yes	No	Yes	Yes	No	No	Unclear	Yes	Yes	Yes	High
Schramm SH et al. [58]	Yes	Yes	No	Yes	No	No	Yes	Unclear	Unclear	Unclear	Yes	High

Q1—Were the two groups similar and recruited from the same population?
Q2—Were the exposures measured similarly to assign people to both exposed and unexposed groups?
Q3—Was the exposure measured in a valid and reliable way?
Q4—Were confounding factors identified?
Q5—Were strategies to deal with confounding factors stated?
Q6—Were the groups/participants free of the outcome at the start of the study (or at the moment of exposure)?
Q7—Were the outcomes measured in a valid and reliable way?
Q8—Was the follow-up time reported and sufficiently long for outcomes to occur?
Q9—Was follow-up complete, and if not, were the reasons for this incomplete follow-up described and explored?
Q10—Were strategies to address incomplete follow-up utilized?
Q11—Was appropriate statistical analysis used?

ISSN: 1129-2377