Table 3. Summary of quality assessment.

Criteria for quality assessment	Percentage meeting criteria (n = 146)
1) Was the outcome of the study clearly defined with measurable standards?	91%
2) Was the measured outcome apparently reported by the standards defining the outcome?	96%
3) Were the factors influencing to the outcome clearly identifiable?	99%
4) Were the inclusion and exclusion criteria clearly stated with at least two components in the section of materials and methods?	90%
5) Was at least one covariate statistically adjusted or were participants randomly assigned to each group?	66%