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Table 2 Subgroup analysis of dietary fiber intake and ovarian cancer risk

From: Dietary fiber intake and reduced risk of ovarian cancer: a meta-analysis

Subgroup Studies, n RR (95% CI) I2 (%) P a P b
Total 11 0.78 (0.70,0.88) 4.20 0.40  
Study design
 Case-control 8 0.77 (0.66,0.90) 25 0.23 0.17
 Cohort 3 0.84 (0.65,1.10) 0 0.70  
Type of control subjects
 Population-based 8 0.82 (0.72,0.94) 0 0.69 0.16
 Hospital-based 3 0.72 (0.52,0.99) 48.20 0.15  
Geographic location
 North America 7 0.79 (0.66,0.95) 19.40 0.28 0.87
 Others 4 0.77 (0.66,0.89) 0 0.41  
No. of cases
 < 300 5 0.83 (0.65,1.07) 15.40 0.32 0.16
 ≥ 300 6 0.77 (0.67,0.87) 5.10 0.38  
Study quality
 NOS < 7 4 0.68 (0.50,0.91) 42.90 0.15 0.09
 NOS ≥7 7 0.84 (0.73,0.96) 0 0.92  
Validation FFQ
 Yes 7 0.81 (0.70,0.93) 0 0.60 0.59
 No 4 0.72 (0.54,0.94) 43.00 0.15  
Fiber type
 Vegetable fiber 3 0.80 (0.55,1.16) 66.90 0.05  
 Fruit fiber 2 0.90 (0.73,1.11) 0 0.32  
 Cereal fiber 3 1.24 (1.02,1.51) 0 0.73  
Fiber source
 Soluble fiber 1 0.79 (0.51,1.23)  
 Insoluble fiber 3 0.60 (0.42,0.86) 61.00 0.08  
Adjustments
BMI
 Yes 3 0.81 (0.69,0.96) 0 0.71  
 No 8 0.77 (0.64,0.92) 25.40 0.23  
Parity
 Yes 10 0.79 (0.70,0.89) 0 0.52  
 No 1 0.43 (0.20,0.93)  
Oral contraceptive use
 Yes 8 0.74 (0.65,0.84) 0 0.54  
 No 3 0.97 (0.76,1.24) 0 0.77  
physical activity
 Yes 6 0.80 (0.70,0.91) 0 0.46  
 No 5 0.73 (0.57,0.94) 24.80 0.26  
Menopausal status
 Yes 6 0.76 (0.67,0.86) 0 0.53  
 No 5 0.86 (0.66,1.11) 28.70 0.23  
  1. Abbreviations: RR relative risk, CI confidence interval, NOS Newcastle–Ottawa Quality Assessment Scale, BMI body mass index, P-valuea, p for heterogeneity within each subgroup, P-valueb., p for heterogeneity between subgroups