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. 2015 Jul 1;5:12044. doi: 10.1038/srep12044

Table 2. Summary of overall and subgroup analyses of the association between folic acid treatment and colorectal cancer risk.

  CRC incidents          
Stratification variablesa Active Control RR (95% CI) Z P> Ph I2(%)
Total population 191 190 1.00 (0.82–1.22) 0.03 0.974 0.821 <0.001
Ethnicity              
 Caucasian 115 126 0.91 (0.71–1.17) 0.73 0.463 0.807 <0.001
 Mixed 74 62 1.19 (0.85–1.67) 1.03 0.303 0.578 <0.001
 Total 189 188 1.00 (0.82–1.23) 0.03 0.974 0.727 <0.001
Age (year)b              
 <mean20,22,24,26 109 119 0.92 (0.71–1.19) 0.67 0.501 0.967 <0.001
 >mean19,23 51 40 1.28 (0.85–1.93) 1.17 0.243 0.227 31.4
 Total 160 159 1.01 (0.81–1.25) 0.05 0.957 0.605 <0.001
Male (%)b              
 <mean22,23,25 22 27 0.78 (0.44–1.37) 0.87 0.384 0.724 <0.001
 >mean19,20,24,25 160 153 1.05 (0.84–1.30) 0.39 0.694 0.542 <0.001
 Total 182 180 1.01 (0.82–1.23) 0.05 0.962 0.727 <0.001
BMI (kg/m2 b              
 <mean20,23 4 7 0.56 (0.17–1.91) 0.92 0.355 0.561 <0.001
 >mean19,22 68 59 1.15 (0.82–1.63) 0.81 0.417 0.188 42.3
 Total 72 66 1.09 (0.78–1.52) 0.51 0.608 0.364 5.9
Dose of folic acidb              
 <mean20,21,23,24,26 102 110 0.92 (0.71–1.21) 0.58 0.562 0.919 <0.001
 >mean19,22,25 89 80 1.11 (0.82–1.50) 0.70 0.485 0.386 <0.001
 Total 191 190 1.00 (0.82–1.22) 0.03 0.974 0.821 <0.001
Durationb              
 <mean19,21,23,25,26 84 73 1.15 (0.84–1.57) 0.86 0.389 0.711 <0.001
 >mean20,22,24 107 117 0.91 (0.70–1.19) 0.68 0.497 0.881 <0.001
 Total 191 190 1.00 (0.82–1.22) 0.03 0.974 0.821 <0.001
Prior Disease              
 Colorectal adenoma19,20,23 14 17 0.81 (0.40–1.62) 0.61 0.544 0.669 <0.001
 CVD19,22,24,25 175 171 1.02 (0.83–1.26) 0.22 0.829 0.477 <0.001
Possible confounding factors              
 Vitamin19,20,22,23,24,25 179 178 1.01 (0.82–1.24) 0.05 0.962 0.605 <0.001
 Antiplatelet drugs19,20,21,23,25 85 75 1.13 (0.83–1.54) 0.77 0.442 0.653 <0.001
 Lipid-lowering drugs19,24 136 128 1.06 (0.84–1.35) 0.50 0.617 0.169 47.1
 Alcohol20,22,23,25,26 45 52 0.86 (0.58–1.28) 0.73 0.466 0.908 <0.001
 Diabetes19,22,24,25 175 171 1.02 (0.83–1.26) 0.22 0.829 0.477 <0.001
 Current smoker19,20,22,26 181 180 1.01 (0.82–1.23) 0.05 0.962 0.727 <0.001
 Hypertension19,22,24 154 150 1.03 (0.82–1.28) 0.23 0.814 0.289 19.4

CVD, cardiovascular disease; CRC, colorectal cancer.

P, P value for association.

Ph, P value for heterogeneity.

aonly articles reporting the variables were analyzed.

bweighted mean of included articles.