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Table 3 Subgroup analyses for the association between trimethylamine N-oxide (TMAO) and stroke

From: Gut microbiota-associated metabolite trimethylamine N-Oxide and the risk of stroke: a systematic review and dose–response meta-analysis

Group No. of studies WMD (95% CI) P within group P between group* Effect model P heterogeneity I2, %
Total 4 2.20 (1.21, 3.18) < 0.001 < 0.001 Random < 0.001 99.7
Study quality
 High 1 0.45 (0.34, 0.57) < 0.001   Fixed
 Moderate 3 2.82 (1.19, 4.46) 0.001   Random < 0.001 99.2
Design     < 0.001    
Case- control 3 2.90 (−0.39, 6.20) 0.085   Random < 0.001 99.7
Nested case-control 1 0.20 (0.15, 0.24) < 0.001    
Sample     < 0.001    
Plasma 2 0.49 (−0.08, 1.07) 0.094   Random < 0.001 99.4
Serum 2 3.96 (−0.08, 8.01) 0.05   Random < 0.001 99.5
Sample size     < 0.001    
< 550 2 3.96 (−0.08, 8.01) 0.055   Random < 0.001 99.5
≥ 550 2 0.49 (− 0.08, 1.07) 0.094   Random < 0.001 99.4
Mean/ median age (y)     < 0.001    
<  60 1 0.45 (0.34, 0.57) < 0.001   Fixed
60–65 3 2.82 (1.19, 4.46) 0.001   Random < 0.001 99.2
% Male     < 0.001    
< 55 2 1.03 (−0.63, 2.69) 0.224   Random < 0.001 98.1
≥ 55 2 3.40 (−1.72, 8.54) 0.194   Random < 0.001 99.9
HTN%     < 0.001    
< 70 1 6.18 (5.47, 6.89) < 0.001   Fixed
≥ 70 2 0.57 (0.32, 0.82) < 0.001   Random 0.018 82.2
N/A 1 1.77 (1.57, 1.97) < 0.001   Fixed
Diabetes %     < 0.001    
< 20 2 3.31 (−2.30, 8.92) 0.248   Random < 0.001 99.6
≥ 20 2 1.24 (0.20, 2.28) 0.019   Random < 0.001 98.4
Current smoking %     < 0.001    
< 30 2 0.57 (0.32, 0.82) < 0.001   Random 0.018 82.2
≥ 30 1 6.18 (5.47, 6.89) < 0.001   Fixed
N/A 1 1.77 (1.57, 1.97) < 0.001   Fixed
  1. Abbreviations: CI Confidence interval, HTN Hypertension, WMD Weighted mean difference *Between groups comparisons are obtained from inverse variance method