Table 2.
Cohort studies included in the meta-analysis
| Study | Study location | All subjects | CRC cases | RR | 95%CI | Control for potential confounding factors2 |
| Clancy et al[50], 2013 | Italy | 266109 | 2420 | 0.84 | 0.76-0.93 | 1-9 |
| Leung et al[49], 2013 | Taiwan | 34205 | 654 | 0.57 | 0.45-0.721 | - |
| Simon et al[51], 2012 | United States | 159219 | 2000 | 0.99 | 0.83-1.20 | 1, 4, 10-27 |
| Jacobs et al[53], 2011 | United States | 133255 | 1739 | 1.03 | 0.94-1.141 | - |
| Lee et al[52], 2011 | United States | 131922 | 1680 | 0.97 | 0.84-1.12 | 1, 6, 10, 12, 13, 28-34 |
| Haukka et al[55], 2010 | Finland | 944962 | 5016 | 1.04 | 0.98-1.101 | - |
| Matsushita et al[54], 2010 | Japan | 13724 | 76 | 1.22 | 0.77-1.94 | - |
| Flick et al[57], 2009 | United States | 69115 | 171 | 0.89 | 0.61-1.30 | 1, 4, 6, 10-13, 15, 18, 19, 28, 35-38 |
| Singh et al[56], 2009 | Canada | 413271 | 6637 | 1.13 | 1.02-1.25 | 1-4, 6, 7, 16, 39-42 |
| Friedman et al[58], 2008 | United States | 4243067 | 5684 | 0.88 | 0.82-0.961 | - |
| Farwell et al[59], 2008 | United States | 62842 | 687 | 0.65 | 0.55-0.78 | 1, 6, 11, 13, 19, 29, 43-53 |
| Setoguchi et al[60], 2007 | United States | 31723 | 249 | 0.96 | 0.70-1.31 | 1-9, 39, 43, 54-64 |
| Friis et al[61], 2005 | Denmark | 334754 | 3006 | 0.85 | 0.65-1.11 | 1, 2, 4, 16, 66 |
Calculated crude relative risk (RR);
1: Age; 2: Sex; 3: Inflammatory bowel disease; 4: Use of nonsteroidal anti-inflammatory drugs; 5: Obesity; 6: Colonoscopy; 7: Comorbidity score; 8: Distinct generic medicines taken; 9: Prior hospitalizations; 10: Body mass index; 11: Smoking status; 12: Family History of colorectal cancer; 13: Alcohol use; 14: Education; 15: Physical activity level; 16: Hormone replacement therapy; 17: Ethnic group; 18: Colorectal polyps; 19: Cardiovascular disease; 20: Calcium intake; 21: Percent energy from fat; 22: Fruit and vegetable intake; 23: Calcium supplement use; 24: Selenium supplement use; 25: Current healthcare provider; 26: Last medical visit within one year; 27: Colon screening; 28: Red meat consumption; 29: Use of aspirin; 30: Calendar year; 31: Study; 32: Pack-years of smoking before age 30; 33: Height; 34: Total energy intake; 35: Hypercholesterolemia; 36: Multivitamin use; 37: Energy-adjusted fibre intake; 38: Folate intake; 39: Benign mammary dysplasia; 40: Coronary heart disease; 41: Resective colorectal surgery; 42: Socioeconomic status; 43: Diabetes; 44: Weight; 45: Thyroid disease; 46: Hypertension; 47: Renal failure; 48: Chest pain; 49: Mental illness; 50: Lung disease; 51: Gastrointestinal Disease; 52: Prostate disease; 53: Total cholesterol; 54: Race; 55: Arthritis; 56: Use of gastroprotective drugs; 57: Estrogen use; 58: Tobacco abuse; 59: Mammography; 60: Gynecologic examination; 61: Pap smear; 62: Fecal occult blood; 63: Number of physician visits; 64: Prior nursing home stay; 65: History of heart attack; 66: Use of cardiovascular drugs. CRC: Colorectal cancer.