Table 2. Studies included in the analysis.

NOS for case-control studies.

NOS, Newcastle-Ottawa Scale

Author	Method	Population	Total number of cases	NOS scale
Natsis et al. (2007) [1]	Natsis	Greek	423	4
Rengachary et al. (1979) [3]	Rengachary	American	226	7
Polguj et al. (2011) [4]	Polguj	Polish	86	6
Raj et al. (2019) [7]	Natsis	Indian	250	5
Soni et al. (2012) [8]	Natsis	Indian	100	4
Adewale et al. (2020) [11]	Rengachary	Ugandan	50	5
Agrawal et al. (2014) [12]	Unclassified	Indian	293	6
Agrawal et al. (2015) [13]	Unclassified	Indian	728	6
Ahmed (2018) [14]	Polguj	Egyptian	65	4
Albino et al. (2013) [15]	Rengachary	Italian	500	4
Benia et al. (2023) [16]	Unclassified	Uruguayan	62	7
Daripelli et al. (2020) [17]	Rengachary	Indian	200	5
Emad et al. (2017) [18]	Natsis	Egyptian	100	6
Inoue et al. (2014) [19]	Rengachary	Japanese	762	5
Inoue et al. (2021) [20]	Rengachary	Japanese	552	5
Iqbal et al. (2009) [21]	Unclassified	Indian	250	4
Jamwal et al. (2018) [22]	Rengachary	Indian	91	5
Kannan et al. (2014) [23]	Rengachary	Indian	400	6
Khalkho et al. (2018) [24]	Rengachary	Indian	69	6
Kumar et al. (2014) [25]	Natsis	Indian	248	5
Mahdy and Shehab (2013) [26]	Natsis	Egyptian	132	5
Nayak and Gujar (2020) [27]	Rengachary	Indian	525	5
Polguj et al. (2013) [28]	Polguj	Polish	616	7
Sangam et al. (2013) [29]	Rengachary	Indian	104	5
Toneva and Nikolova (2014) [30]	Unclassified	Bulgarian	102	5
Ukoha et al. (2022) [31]	Rengachary	Nigerian	193	5
Vyas et al. (2012) [32]	Polguj	Indian	300	5
Wang et al. (2011) [33]	Natsis	Chinese	295	5
Yamakado (2016) [34]	Rengachary	Japanese	760	6
Yang et al. (2012) [35]	Unclassified	Korean	103	7
Zhang et al. (2019) [36]	Unclassified	Chinese	308	4