Table 5. Quality appraisal using the Newcastle-Ottawa classification tool for cross-sectional studies.

*Demonstration of degree of approval per guidelines in the Newcastle-Ottawa classification tool

Article	Representativeness *	Sample size *	Non-respondents *	Ascertainment of exposure **	The subjects in different outcome groups are comparable, based on the study design or analysis. Confounding factors are controlled. **	Assessment of the outcome           *****	Statistical test      *	Long follow-up	Adequacy of follow-up	Accept/Reject (%)
Lelonek-Kuleta and Bartczuk [14]	*	*	*	*	*	****	*	-	-	Accept 67%
Soares et al. [15]	-	*	*	*	**	***	*	-	-	Accept 60%