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Table 2 Subgroup analysis of whole grains intake and risk of colorectal cancer

From: Association of whole grains intake and the risk of digestive tract cancer: a systematic review and meta-analysis

Subgroups No. of studies No. of Participants (Cases) RR (95% CI) P Heterogeneity Test
Chi-Square I2 phet
All studies 18 1,489,581(19424) 0.89(0.84,0.93) < 0.001 38.82 38% 0.029
Study design
 Cohort 11 1,481,538(15519) 0.91(0.88,0.94) < 0.001 22.95 30.3% 0.115
 Case-control 7 8043(3905) 0.95(0.91,1.00) 0.030 13.33 47.5% 0.064
Sex
 Men 7 236,055(4826) 0.80(0.69,0.92) 0.001 14.07 50.3% 0.050
 Women 8 454,822(7126) 0.94(0.89,0.99) < 0.001 6.25 0% 0.619
Geographic locations
 Europe 5 311,476(3599) 0.84(0.75,0.93) 0.001 4.40 0% 0.732
 America 10 1,176,927(15769) 0.92(0.88,0.95) < 0.001 19.83 34.5% 0.099
Publication year
 Before 2010 9 854,956(8822) 0.82(0.76,0.89) < 0.001 8.07 0% 0.622
 After 2010 9 634,625(10602) 0.94(0.91,0.97) < 0.001 21.73 40.2% 0.060
Sample size
  ≥ 500 14 1,488,346(18809) 0.91(0.88,0.94) < 0.001 27.76 27.9% 0.115
  < 500 4 1235(615) 0.76(0.51,1.12) 0.170 8.20 63.4% 0.042
Adjustment for energy
 Yes 9 881,482(10198) 0.85(0.79,0.92) < 0.001 10.48 4.6% 0.399
 No 9 608,299(9226) 0.94(0.91,0.97) < 0.001 21.84 40.5% 0.058