Table 2. Characteristics of the Studies Included in the Meta-Analysis.

Study authors	Year of publication	Nature of the study	H. pylori positive		Mean age
			Cases	Controls	Cases	Controls
Abdel-Razik et al [22]	2020	Prospective cohort	16/23	254/535	55	55
Al-Soud et al [26]	2008	Retrospective	7/12	3/24	63	36.5
Avenaud et al [27]	2000	Retrospective	5/5	1/8	67.6	45.25
Coppola et al [23]	2003	Retrospective	0/21	0/34	68	60.5
Dore et al [28]	2002	Retrospective	6/11	5/30	65.2 ± 8.8	51.2 ± 15
Esmat et al [29]	2012	Retrospective	12/16	18/69	N/A	N/A
Fan et al [30]	2002	Retrospective	9/15	0/13	48.5	N/A
Fotouhi et al [31]	2011	Retrospective	7/22	3/37	N/A	N/A
Giannini et al [19]	2003	Retrospective	23/33	41/55	64.6 ± 9	55
Qu et al [20]	2017	Case-control	49/61	813/1,521	35.3 ± 15.7	36.6 ± 14.5
Huang and Cui [32]	2017	Retrospective	86/148	253/460	52.4 ± 11.6	53.7
Huang et al [33]	2004	Retrospective	8/20	0/16	42	36
Ito et al [34]	2004	Retrospective	13/15	0/17	59.2	N/A
Leelawat et al [35]	2007	Retrospective	12/12	5/7	54	59
Leone et al [21]	2003	Case-control	36/46	25/46	60	69
Rocha et al [36]	2005	Cross sectional	16/31	18/78	57.8	49
Mekonnen et al [37]	2018	Prospective case-control	37/60	14/60	36	51
Murphy et al [38]	2014	Case-control	91/97	198/224	58	57
Pellicano et al [25]	2004	Cross-sectional	17/20	2/6	N/A	N/A
Verhoef et al [39]	2003	Cross-sectional	9/20	3/31	61	62
Vivekanandan et al [24]	2008	Retrospective	0/22	5/60	52.8 ± 14	N/A
Xuan et al [17]	2006	Cross-sectional	17/28	18/77	N/A	N/A
Yang et al [18]	2013	Cross-sectional	35/50	37/100	56.9 ± 9.5	54.8 ± 11.4
Nilsson et al [40]	2001	Cross-sectional	12/16	0/20	N/A	N/A
Zhang et al [41]	2004	Cross-sectional	16/48	2/37	N/A	N/A
Li et al [42]	2006	Cross-sectional	22/34	0/20	N/A	N/A

H. pylori: Helicobacter pylori.