Table 2.

Criteria for assessing risk of bias for observational studies by Sanderson et al. [29].

Author	Selection Bias Sampling Source and Methods, with Inclusion/Exclusion Criteria	Measurement Bias Exposure and/or Outcome Measurement	Design Specific Bias Attrition Recall	Confounding Bias	Statistical Method Bias Primary Analysis of Effect	Conflict of Interest or Funding Source
Creedy et al. [32]	H	UC	L	L	L	H
Dawson et al. [33]	H	H	L	L	L	H
Dixon et al. [34]	H	H	L	L	L	H
Fenwick et al. [35]	H	UC	L	L	UC	H
Fenwick et al. [44]	H	H	L	L	L	L
Henriksen & Lukasse [41]	H	H	L	UC	UC	H
Hildingsson et al. [42]	H	H	L	L	L	L
Hunter et al. [43]	H	H	H	L	L	H
Jepsen et al. [39]	H	H	L	UC	L	L
Jordan et al. [36]	H	H	L	L	L	L
Kristensen et al. [5]	H	L	L	L	L	H
Newton et al. [37]	H	H	UC	L	UC	H
Sidebotham et al. [38]	H	L	L	L	L	L
Stoll & Gallagher [40]	H	H	L	L	L	UC

Note: H: High; L: Low; UC: Unclear.