Table 1. Quality assessment of studies according to the adapted Newcastle-Ottawa Scale.

	Selection				Comparability	Results
Studies	Sample representativeness	Sample size	Answer rate	Risk factor	Adequacy of design and analysis	Evaluation of results	Appropriate statistical analyses	Score
Androulidakis and Jones (2006) 19	–	–	*	–	*	**	*	5
Epp et al. (2013) 14	–	–	*	**	*	**	*	7
Zhang et al. (2014) 15	–	–	*	*	*	**	*	6
Maamor and Billings (2017) 16	–	–	*	**	*	**	*	7
Tanner et al. (2019) 17	–	–	*	*	*	**	*	6
Rocha et al. (2022) 18	–	–	*	*	*	**	*	6

Note: Score classification: high quality (9–6); moderate quality (4–5); and low quality (< 4).