Table 1.

Newcastle-Ottawa scale of studies included in the systematic review.

Study	Selection				Comparability	Outcome			Total
	Representativeness of the exposed cohort	Selection of non-exposed cohort	Ascertainment of exposure	Demonstration that outcome was not present at start of study	Comparability of cohorts	Assessment of outcome	Follow up duration	Adequacy of follow up
Kirkizlar et al	*		*	*		*		*	5
Durmus et al	*		*	*		*	*	*	6
Kartal et al	*	*	*	*		*	*	*	7
Builes et al	*		*	*		*	*	*	6
Yabanoglu et al	*		*	*		*	*	*	6
Saie et al	*		*	*		*	*	*	6
Ozdemir et al	*		*	*		*	*	*	6
Ali et al	*	*	*	*		*	*	*	7
Simsir et al	*		*	*		*	*	*	6
Calissendorff et al	*		*	*		*		*	5
Fischli et al	*		*	*		*	*	*	6
Keklik et al	*	*	*	*		*	*	*	6
Ezer et al	*		*	*		*	*	*	6
Panzer et al	*		*	*		*	*	*	6
Apaydin et al	*		*	*		*	*	*	6
Akin et al	*		*	*		*	*	*	6

(*) indicates a point that can be awarded for an answer to a question