Table 1

Modified Downs and Black checklist (risk of bias assessment) for the six cohort, clinical trial studies

Study
item
Reporting External validity Internal validity (study bias) Internal validity—confounding (selection bias) Power Score (out of 28) Per cent
123456789101112131415161718192021222324252627
Cha et al25 1111111011000001111110100101760.7%
De Mey et al27 1111211111000001111101000101864.3%
Lee et al22 1111211011000000111100000001450.0%
Merolla et al23 1111211010110001101100000011657.1%
Merolla et al24 1111211010000000100100000011242.9%
Osteras et al26 1111111111000001110111101011967.9%