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

Table 5 Assessment of risk of bias for case–control studies according to the Joanna Briggs Institute (JBI) checklist

Study authors	Q1	Q2	Q3	Q4	Q5	Q6	Q7	Q8	Q9	Q10	Overall risk of bias assessment
Lambru G et al. [62]	Yes	Yes	Yes	No	Yes	Yes	Yes	Yes	Yes	Yes	Low
Lund N et al. [61]	Yes	Yes	Yes	No	Yes	Yes	No	Yes	Unclear	Yes	Moderate
Özcan RK et al. [49]	Yes	No	Yes	Yes	Yes	Unclear	Unclear	Yes	No	Yes	High
Sarker MA et al. [50]	Yes	Yes	Unclear	Yes	Yes	Yes	Yes	Yes	Unclear	Yes	Low
Kim BS et al. [53]	Yes	Yes	Yes	No	Yes	Yes	No	Yes	No	Yes	Moderate
Gür-Özmen S et al. [54]	Yes	Unclear	Yes	No	Yes	Yes	Yes	Yes	Unclear	Yes	Moderate

Q1—Were the groups comparable other than the presence of disease in cases or the absence of disease in controls?
Q2—Were cases and controls matched appropriately?
Q3—Were the same criteria used for identification of cases and controls?
Q4—Was exposure measured in a standard, valid and reliable way?
Q5—Was exposure measured in the same way for cases and controls?
Q6—Were confounding factors identified?
Q7—Were strategies to deal with confounding factors stated?
Q8—Were outcomes assessed in a standard, valid and reliable way for cases and controls?
Q9—Was the exposure period of interest long enough to be meaningful?
Q10—Was appropriate statistical analysis used?

ISSN: 1129-2377