Table 4.

Newcastle–Ottawa Quality Assessment Scale (NOS) for studies included in the systematic review

Author name	Study design	Selection				Comparability	Outcome
		Representativeness of the sample	Sample size	Non-respondents	Ascertainment of the exposure		Assessment of the outcome	Statistical test	Final score
Galilea-Zabalza et al. [36]	Cross-sectional	*	–	*	*	*	**	*	8
Bonaccio et al. [35]	Cross-sectional	*	*	*	*	**	**	*	9
Milte et al. [46]	Cross-sectional	*	*	*	*	**	**	*	9
Alcubierre et al. [34]	Cross-sectional	*	*	-	*	*	**	*	7
Holmes et al. [22]	Cross-sectional	*	*	-	-	*	**	*	6
Kim et al. [17]	Cross-sectional	*	*	*	*	**	**	*	9
Zaragoza-Marti et al. [45]	Cross-sectional	*	*	-	*	*	*	*	6
Moravejolahkami et al. [47]	Cross-sectional	*	*	*	*	**	**	*	9
Mozzillo et al. [21]	Cross-sectional	*	*	*	*	**	**	*	9

Author name	Study design	Selection				Comparability	Outcome
		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		Assessment of outcome	Was follow-up long enough for outcomes to occur	Adequacy of follow up of cohorts	Final score
Ruano et al. [28]	Cohort	*	*	*	*	**	*	*	*	9
Perez-Tasigchana et al. [23]	Cohort	*	*	*	*	**	*	*	*	9
Perez-Tasigchana et al. [23]	Cohort	*	*	*	*	**	*	*	*	9
Gigic et al. [27]	Longitudinal	*	*	*	*	**	*	*	*	9
Sanchez-Aguadero et al. [44]	Longitudinal	*	*	*	*	**	*	*	*	9

One star represents a score of 1, and a study can be awarded a maximum score of 9 in total. The items were scored “*”if the answer was “YES,” and “−” if the answer was “NO” or “UNCLEAR.” The final quality scores were as follows: low quality = 0–3; moderate quality = 4–6; high quality ≥ 7