Table 1.

Characteristics of included studies: country, setting and population

References	Country (population)	Settinga		Cases and controls
				Cases (N)	Controls (N)
		Hosp	Other		All	HC	NM	PM
Gastric cancer only
Cai et al. [23]	China	×	–	60	60	60	0	0
Chen et al. [24]	China	×	×	249	1203	0	1203	0
Chen et al. [25]	China	×	–	87	105	40	65	0
Chung et al. [26]	South Korea	×	–	147	94	Ub	Ub	24
Ding et al. [27]	China	×	–	110	110	110	0	0
Dong et al. [28]	China	×	–	90	57	57	0	0
Gantuya et al. [29]	Mongolia	×	–	50	752	0	752	0
Gwak et al. [30]	South Korea	U	U	96	187	0	187	0
He et al. [31]	China	×	–	149	235	124	111	0
Hoshino et al. [32]	Japan	–	×	248	74	74	0	0
Huang et al. [33]	China	×	–	197	125	37	88	0
Huang et al. [34]	China	×	×	62	59	59	0	0
Huang et al. [35]	China	×	–	60	60	60	0	0
Iwasaki et al. [36]	Japan	×	–	54	54	54	0	0
Ji et al. [37]	China	×	–	168	74	74	0	0
Juan Cai et al. [38]	China	×	–	106	358	160	198	0
Kaise et al. [39]	Japan	×	–	187	561	561	0	0
Kang et al. [40]	South Korea	×	–	380	626	228	291	107
Kikuchi et al. [41]	Japan	×	–	122	178	79	99	0
Kim et al. [42]	South Korea	×	–	120	120	Ub	Ub	0
Kurilovich et al. [43]	Russia	–	×	52	104	104	0	0
Li et al. [44]	China	×	–	60	60	60	0	0
Li et al. [45]	China	×	–	79	112	81	0	31
Li et al. [46]	China	×	–	65	65	65	0	0
Li et al. [47]	South Korea	×	–	100	100	100	0	0
Li et al. [48]	China	×	–	234	428	270	0	158
Lim et al. [49]	South Korea	×	–	100	90	Ub	Ub	30
Lim et al. [50]	South Korea	×	–	100	100	Ub	Ub	30
Lin et al. [51]	China	U	U	51	78	60	18	0
Liu et al. [52]	China	×	–	142	105	105	0	0
Liu et al. [53]	China	×	–	119	148	99	49	0
Liu et al. [54]	China	×	–	50	50	50	0	0
Meistere et al. [55]	Taiwan, Latvia, Lithuania, Germany	×	×	829	929	929	0	0
Mroczko et al. [56]	Poland	×	–	73	61	61	0	0
Ning et al. [57]	China	×	–	169	75	75	0	0
Oue et al. [58]	Japan	×	–	123	96	76	20	0
Pan et al. [59]	China	×	–	81	130	77	53	0
Park et al. [60]	South Korea	×	–	81	103	32	63	8
Parvaee et al. [61]	Iran	–	×	50	50	50	0	0
Qin et al. [62]	China	×	×	407	407	407	0	0
Qiu et al. [63]	China	×	–	200	200	200	0	0
Song et al. [64]	China	–	×	68	68	0	68	0
Su et al. [65]	China	×		82	59	50	9	0
Sun et al. [66]	China	×	×	332	332	332	0	0
Tsalikidis et al. [67]	Greece	×	–	99	78	78	0	0
Wang et al. [68]	Taiwan	U	U	170	116	116	0	0
Wang et al. [69]	China	×	–	72	54	54	0	0
Wang et al. [70]	China	×	×	186	186	186	0	0
Wang et al. [71]	China	×	–	60	120	60	60	0
Werner et al. [72]	Germany	–	×	146	97	97	0	0
Wu et al. [73]	China	×	–	90	90	90	0	0
Wu et al. [74]	China	×	–	99	132	100	30	2
Wu et al. [75]	China	×	–	201	318	157	161	0
Yanaoka et al. [76]	Japan	–	×	63	5146	5146	0	0
Yang et al. [77]	South Korea	–	×	290	290	290	0	0
Yang et al. [78]	China	×	–	109	106	0	106	0
Yoon et al. [79]	South Korea	×	×	500	200	200	0	0
Yun et al. [80]	China	×	–	194	376	185	191	0
Zayakin et al. [81]	Latvia, Germany	×	–	235	367	213	154	0
Zhang et al. [82]	China	×	–	114	298	187	111	0
Zhang et al. [83]	China	×	×	80	70	0	70	0
Zhang et al. [84]	China	×	–	80	80	0	80	0
Zhou et al. [85]	China	×	–	50	50	Ub	Ub	Ub
Zhou et al. [86]	China	×	–	71	61	61	0	0
Zhou et al. [87]	China	×	–	70	70	70	0	0
Pancreatic cancer only
Akita et al. [88]	Japan	×	–	116	138	138	0	0
Balasenthil et al. [89]	USA	–	×	98	154	61	93	0
Brand et al. [90]	USA	×	–	173	120	120	0	0
Cao et al. [91]	China	×	–	156	115	0	57	58
Capello et al. [92]	USA	×	–	73	134	60	74	0
Chung et al. [93]	South Korea	×	–	55	93	70	23	0
Chung et al. [94]	South Korea	×	–	54	80	55	25	0
Deng et al. [95]	China	×	–	303	640	600	40	0
Duraker et al. [96]	Turkey	×	–	123	173	0	173	0
Firpo et al. [97]	USA	×	×	75	261	150	84	27
Fukutake et al. [98]	Japan	×	–	240	7800	7772	28	0
Gao et al. [99]	China	×	–	70	120	50	70	0
Gold et al. [100]	USA	–	×	53	130	43	87	0
Gold et al. [101]	USA	×	×	298	199	79	120	0
Groblewska et al. [102]	Poland	U	U	62	65	65	0	0
Guo et al. [103]	China	×	–	250	300	150	150	0
Honda et al. [104]	Japan, Germany	×	–	319	291	181	110	0
Honda et al. [105]	Japan, USA	×	×	384	342	192	150	0
Honda et al. [106]	Ten European countriesc	–	×	156	213	213	0	0
Jiang et al. [107]	China	×	–	96	252	200	52	0
Kaur et al. [108]	USA	×	–	154	167	0	167	0
Kim et al. [109]	USA	×	×	278	418	220	83	115
Kuwatani et al. [110]	Japan	×	–	98	158	105	21	32
LeCalvez-Kelm et al. [111]	Czech Republic, Slovakia	×	×	397	533	374	159	0
Lee et al. [112]	South Korea	×	–	51	112	0	112	0
Liao et al. [113]	Taiwan	×	×	58	146	102	44	0
Liu et al. [114]	China	×	–	138	175	68	107	0
Liu et al. [115]	China	×	–	172	215	133	82	0
Liu et al. [116]	China	–	×	235	470	240	230	0
Matsubara et al. [117]	Japan	×	–	140	97	87	0	10
Mayerle et al. [118]	Germany	–	×	79	160	80	80	0
Mellby et al. [119]	Denmark, USA	–	×	143	276	219	57	0
Mizuno et al. [120]	Japan	×	–	180	180	84	96	0
O'Brien et al. [121]	UK	–	×	101	184	184	0	0
Park et al. [122]	South Korea	–	×	139	146	74	72	0
Park et al. [123]	South Korea	U	U	292	165	94	71	0
Peng et al. [124]	Taiwan	×	×	263	230	185	45	0
Poruk et al. [125]	USA	×	×	86	134	86	48	0
Ritchie et al. [126]	Canada	–	×	84	99	99	0	0
Rychlikova et al. [127]	Czech Republic	×	–	64	185	48	137	0
Sakai et al. [128]	Japan	×	–	53	147	102	22	23
Song et al. [129]	USA	–	×	188	220	89	68	63
Tachezy et al. [130]	Germany	×	×	116	243	128	115	0
Talar-Wojnarowska et al. [131]	Poland	×	–	85	122	50	72	0
Tavano et al. [132]	Italy	×	–	74	117	117	0	0
Ward et al. [133]	UK	×	–	75	61	0	61	0
Xu et al. [134]	China	×	–	156	180	65	57	58
Zhang et al. [135]	China	×	–	129	278	183	95	0
Zhang et al. [136]	China	×	–	67	206	145	61	0
Zhong et al. [137]	China	×	–	183	202	141	61	0
Zhou et al. [138]	China	×	–	152	207	96	91	20
Zhou et al. [139]	China	×	–	156	199	163	36	0
Zhou et al. [140]	China	×	–	64	64	64	0	0
Oesophageal cancer only
Bagaria et al. [141]	India	×	–	50	50	50	0	0
Bai et al. [142]	China	×	–	89	125	80	14	31
Bagaria et al. [143]	India	×	–	50	50	50	0	0
Brockmann et al. [144]	Germany	×	–	50	150	50	100	0
Huang et al. [145]	China	×	–	60	60	60	0	0
Jia et al. [146]	China	×	–	101	98	98	0	0
Liao et al. [147]	China	×	–	151	230	194	36	0
Lukaszewicz-Zajac et al. [148]	Poland	×	–	56	65	65	0	0
Lv et al. [149]	China	×	–	126	80	80	0	0
Pan et al. [150]	China	×	–	50	110	60	50	0
Peng et al. [151]	China	×	–	104	53	53	0	0
Sudo et al. [152]	Japan	×	×	283	9364	9203	161	0
Wang et al. [153]	China	×	–	84	154	154	0	0
Xing et al. [154]	China	×	–	169	154	80	74	0
Xu et al. [155]	China	×	–	237	134	134	0	0
Xu et al. [156]	China	×	–	70	80	80	0	0
Yan et al. [157]	China	×	–	364	229	229	0	0
Zhang et al. [158]	China	×	–	81	81	81	0	0
Zhang et al. [159]	China	×	–	62	58	58	0	0
Zhang et al. [160]	China	×	–	81	81	81	0	0
Zhang et al. [161]	China	×	–	186	186	186	0	0
Zhang et al. [162]	China	×	–	112	112	112	0	0
Zheng et al. [163]	China	×	–	150	185	126	59	0
Zhou et al. [164]	China	–	×	88	479	200	0	279
Biliary tract cancers only
Deng et al. [165]	China	×	–	153	65	0	65	0
Leelawat et al. [166]	Thailand	×	–	59	128	0	128	0
Wang et al. [167]	China	×	–	78	156	78	78	0
More than one tumour type
Bagaria et al. [168]	India	×	–	50 GC 50 OC	50	50	0	0
Markar et al. [169]	UK	×	–	163 GC or OC	172d	89	82	0
Ren et al. [170]	China	×	–	1049 GC 268 OC 160 PaC	1019	747	272	0
Schneider et al. [171]	Germany	U	U	122 GC 86 OC	53	53	0	0

GC gastric cancer, HC healthy control, Hosp hospital, NM non-malignant, OC oesophageal cancer, PaC pancreatic cancer, PM pre-malignant, U unclear, UK United Kingdom, USA United States of America

^aDue to wide variations in health systems across different countries, hospital setting is a broad definition than can encompass secondary and tertiary care. Other setting refers to biobanks, reference sets, databases, or archived samples; general population cohorts or cohorts from population screening programmes; or cohorts from previous trials or observational studies

^bIn most of these studies, unclear numbers refer to healthy controls and non-malignant conditions combined (70 controls for [26], 120 controls for [42], 60 controls for [49], and 70 controls for [50]). In the case of Zhou et al. [85], it is also unclear whether controls had pre-malignant conditions

^cDenmark, France, Italy, Germany, Greece, Spain, UK, Norway, Sweden & Netherlands

^dSum of controls does not add up to total number of controls (mismatch in paper)