Table 1 Summary of characteristics of included 11 studies

Number of participants (%) (Mean ± SD)

553 (100%) (52 ± 42)

480 (100%) (45 ± 28)

1033 (100%) (48 ± 35)

Male

124 (22.4%)

118 (24.6%)

242 (23.4%)

Female

429 (77.6%)

362 (75.4%)

791 (76.6%)

Age (Mean ± SD)^a

45.0 ± 6.7

43.9 ± 6.8

44.5 ± 6.9

BMI (kg/m²)

24.3 ± 2.2

24.5 ± 1.8

24.4 ± 1.9

Diagnostic criteria,

N. of study

Percentage

Fukuda

9

N/A

69.2%

Canadian

3

N/A

23.1%

ICC

1

N/A

17.7%

Participants with GI disorder

 IBS (4 studies)

177/273 (64.8%)

10/280 (3.6%)

187/553 (33.8%)

 GID (4 studies)

34/98 (34.7%)

17/87 (19.5%)

51/185 (27.6%)

 N/A (3)

182

113

295

Gut microbiome detection methods (Number of study, %)

 16 s/18 s rRNA (7, 63.6%)

Shotgun (3, 27.3%)

Culture (1, 9.1%)

Instruments, Number of study (%)

 Illumina MiSeq

Illumina HiSeq

Roche 454

MALDI-TOF MS

5 (45.5%);

3 (27.3%)

2 (18.2%)

1 (9.1%)

Gut microbiota analysis tools, N. of study (%)

 QIIME 1/2

R

Mothur

MBT

RDP Classifier

 5 (45.4%)

2 (18.2%)

2 (18.2%)

1 (9.1%)

1 (9.1%)

Publication Year, Number of study (%)

2013–2020 (7 studies, 63.6%)

2021–2023 May (4 studies, 36.4%)

Continents, Number of study (%)

 North America

Europe

Oceania

Asia

 7 (63.6%)

2 (18.2%)

1 (9.1%)

1 (9.1%)