Table 1. Baseline characteristics of included studies for meat intake and colorectal adenomas risk.
| First author, year, country | Study design | Case/control (cohort, n) | Study period | Type of dietary exposure | Dietary exposure categories | Adjusted RRs (95% CI) (highest to lowest) | Adjusted variables | NOS score |
|---|---|---|---|---|---|---|---|---|
| Giovannucci 1992 USA [12] | co | 170/7284 | 1986–1988 | Red meat | Quintile | 1.23 (0.70–2.14) | Age, total energy intake, family history of CRC | 7 |
| Sandler 1993 USA [13] | cc | 236/409 | 1988–1990 | Beef | Quintile | 1.78 (0.97–3.27) | Age, alcohol, BMI, calories | 6 |
| Haile 1997 USA [14] | cc | 488/488 | 1991–1993 | Beef Processed meat | Quintile | 1.83 (1.12–2.99) 1.48 (0.92–2.39) | Age, gender, NSAIDs use, fat, vegetable, protein, carbohydrates, fiber, cholesterol, BMI, physical activity, calories, smoking, ethnicity | 7 |
| Lubin 1997 Israel [15] | cc | 196/196 | 1979–1989 | Beef | Tertile | 1.60 (0.90–2.70) | Energy intake and physical activity | 6 |
| Breuer-Katschinski 2001 Germany [16] | cc | 184/184 | 1993–1995 | Beef | Quintile | 3.10 (1.46–6.43) | Energy, relative weight and social class | 6 |
| Nagata 2001 Japan [17] | co | 279/28361 | 1992–1995 | Beef and pork | Middle vs highest | 1.06 (0.77–1.46) | Age, total energy, smoking, alcohol | 6 |
| Voskuil 2002 Netherlands [18] | cc | 119/148 | 1995–1998 | Red meat | Tertile | 1.20 (0.12–12.00) | Age, gender, energy intake | 6 |
| Tiemersma 2004 Netherlands [19] | cc | 431/433 | 1997–2000 | Red meat | Quartile | 1.20 (0.80–1.80) | Age, gender, and indication of endoscopy | 7 |
| Chan 2005 USA [20] | ncc | 527/527 | 1976–1990 1990–1998 | Red meat | Quartile | 1.57 (0.93–2.65) | Age, fasting status, date of blood draw, history of previous endoscopy, BMI, smoking, physical activity, calcium, folate, alcohol, multivitamins, aspirin, menopause status | 8 |
| Sinha 2005 USA [21] | ncc | 3498/34817 | 1993–2001 | Red meat Processed meat | Quintile | 1.07 (0.92–1.24) 1.04 (0.90–1.19) | Age, gender, screening center, energy intake, ethnicity, education, tobacco use, alcohol, use of aspirin and ibuprofen separately, physical activity, total folate intake, calcium intake, dietary fiber intake | 9 |
| Wu 2006 USA [22] | co | 581/14032 | 1996–2002 | Red meat Processed meat | Quintile | 1.18 (0.87–1.62) 1.52 (1.12–2.08) | age, family history of CRC, reason for endoscopy, negative endoscopy before 1996, physical activity, smoking, race, aspirin use, total energy intake, calcium and folate intake | 8 |
| Cho 2007 USA [23] | co | 2408/39246 | 1984–2002 | Red meat | Quintile | 1.41 (1.11–1.79) | age, smoking, BMI, physical activity, family history of CRC, history of endoscopic screening, year of endoscopy, aspirin use, menopausal status and HRT, energy intake, alcohol, folate, total fiber and calcium | 9 |
| Saebo 2008 Norway [24] | cc | 422/222 | 1995–1999 | Red meat | Tertile | 1.22 (0.78–1.91) | Age, gender | 6 |
| Ferrucci 2009 USA [25] | cs | 158/649 | 2000–2002 | Red meat Processed meat | Quartile | 2.02 (1.06–3.83) 1.05 (0.59–1.85) | Age, education, race, smoking, physical activity, BMI, study center, HRT, family history of colorectal polyps or CRC, NSAIDs use, alcohol, fiber, calcium, total caloric intake | 7 |
| Ramadas 2009 Malaysia [26] | cc | 59/59 | Jan-Dec 2005 | Red meat | ≥ 3 vs. < 3 times/week | 2.51 (1.00–6.28) | Age, ethnicity, gender, physical activity, height, BMI, waist circumference, energy intake, drinking and smoking | 6 |
| Rohrmann 2009 Europe [27] | co | 516/25540 | 1998–2007 | Red meat | Quartile | 1.33 (0.95–1.85) | Energy intake without energy from alcohol, ethanol intake, milk and milk product, fiber, BMI, family history of CRC, physical activity, NSAID, smoking, education, age and sex | 8 |
| Northwood 2010 UK [28] | cc | 317/296 | No | Red meat | Quartile | 0.85 (0.53–1.36) | Age and sex | 6 |
| Wang 2011 USA [29] | cc | 914/1185 | 1995–2007 | Red meat Processed meat | Tertile | 1.11 (0.83–1.48) 1.23 (0.94–1.61) | Age, sex, ethnicity, daily energy intake, physical activity, recruitment site and examination procedure, BMI, smoking, alcohol, folate | 8 |
| Burnett-Hartman 2011 USA [30] | cc | 519/772 | 2004–2007 | Red meat | Tertile | 1.19 (0.80–1.78) | Age, gender, race, education, BMI, alcohol, NSAIDs use, HRT | 8 |
| Fu 2011 USA [31] | cc | 1881/3764 | 2003–2010 | Red meat Processed meat | Quartile | 1.40 (1.20–1.60) 1.30 (1.10–1.50) | Age, sex, race, study site, education, indications for colonoscopy, smoking, alcohol, BMI, physical activity, regular NSAIDs use, total energy intake, recruitment before or after colonoscopy | 9 |
| Ferrucci 2012 USA [32] | co | 1008/17072 | 2001–2009 | Red meat Processed meat | Quartile | 1.22 (0.98–1.52) 1.23 (0.99–1.54) | age, study center, gender, ethnicity, education, family history of CRC, BMI, NSAID use, physical activity, smoking, alcohol, supplemental calcium, dietary fiber, total energy intake | 9 |
| Nimptsch 2013 USA [11] | co | 1494/19771 | 1998–2007 | Red meat Processed meat | Quartile | 0.96 (0.74–1.23) 0.92 (0.76–1.11) | age, family history of CRC, endoscopy, height, BMI, smoking, physical activity, aspirin use, high school/adult energy intake, alcohol | 9 |
| Cross 2014 USA [10] | cc | 131/131 | 1994–1996 | Red meat Processed meat | Quartile | 1.40 (0.66–2.96) 0.98 (0.43–2.23) | Age, sex, education, race, BMI, family history of CRC, smoking, physical activity, fiber intake | 7 |
| Budhathoki 2015 Japan [9] | cc | 738/697 | 2004–2005 | Red meat Processed meat | Quartile | 1.19 (0.87–1.63) 1.28 (0.92–1.78) | Age, screening period, smoking, alcohol, BMI, physical activity, family history of CRC, NSAIDs use. Further adjusted for age at menopausal status, and HRT in women | 8 |
| Mathew 2004 USA [33] | RCT recurrence | 958/947 | 1994–1998 | Red meat Processed meat | Quintile | 0.98 (0.71–1.35) 0.92 (0.68–1.25) | age, sex and group | |
| Robertson 2005 USA [34] | co recurrence | 539/1519 | 1984–1988 | Red meat Processed meat | Quartile | 0.97 (0.78–1.21) 1.15 (0.92–1.43) | age, sex, clinical center, treatment category, study, the duration of the observation period | 8 |
| Martinez 2007 USA [35] | RCT recurrence | 379/869 | 1995–1999 | Red meat Processed meat | Tertile | 1.06 (0.72–1.55) 1.29 (0.89–1.86) | age, sex, previous polyps and number of colonoscopies during follow-up |
CRC: colorectal cancer; RCT: randomized controlled trial; co: cohort; ncc: nested case-control; cc: case-control; cs: cross-sectional; RRs: relative risks; 95% CI: 95% confidence intervals; BMI: body mass index; NSAIDs: nonsteroidal anti-inflammatory drugs; HRT: hormone replacement therapy.