Table 2.

Result of quality assessment using the Newcastle-Ottawa Scale for the cohort study

Study	Selection				Comparability	Outcome			NOS score
	Representativeness of the exposed cohort	Selection of the non exposed cohort	Ascertainment of exposure	Demonstration that outcome of interest was not present at start of study	Comparability of cohorts on the basis of the design or analysis	Assessment of outcome	Follow-up long enough for outcomes to occur	Adequacy of follow up of cohorts
Hasan M Al-Musa,2016	☆	☆	☆	☆	☆	☆	☆	☆	8
A. Ishay,2005	☆		☆	☆	☆	☆	☆	☆	7