Table 2.
The baseline characteristics of included studies on blood vitamin B12 level and colorectal cancer
| Study | Country | Study name | Study type | Age (years) | Cancer site | No. of cases/controls | Exposure dose (pmol/l)* | Study quality† | Adjusted variables |
|---|---|---|---|---|---|---|---|---|---|
| Van Guelpen et al. (2010)( 39 ) | Sweden | VIP Study, MONICA Study and MSP Study | CCS | NR | CRC: CIMP-low/high | 91/181 | M: ≤220 (Q1), >351 (Q4) F: ≤232 (Q1), >392 (Q4) | 6 | BMI, current smoking, recreational PA, alcohol intake |
| 62·5 (range 56·7–66·9) | CRC: CIMP-negative | 92/183 | M: ≤220 (Q1), >351 (Q4) F: ≤232 (Q1), >392 (Q4) | ||||||
| Le Marchand et al. (2009)( 40 ) | USA | Multiethnic Cohort | CCS | 63–76 | CRC | 224/411 | ≤361 (Q1), >722 (Q4) | 7 | Age at blood draw, hours of fasting prior to blood draw, hours of moderate or vigorous PA, processed meat, pack-years, BMI, ethanol, family history of CRC, history of CRC, plasma folate |
| Weinstein et al. (2008)( 41 ) | USA | ATBC Study | CCS | 54–62 | CRC | 275/275 | ≤243 (Q1), >529 (Q5) | 6 | Age, BMI, occupational and leisure PA, intakes of vitamin D and Fe |
VIP, Västerbotten Intervention Programme; MONICA, MONitoring of trends and determinants in CArdiovascular disease; MSP, Mammography Screening Project; ATBC, Alpha-Tocopherol, Beta-Carotene Cancer Prevention; CCS, case–control study; NR, not reported; CRC, colorectal cancer; CIMP, CpG island methylator phenotype; M, males; F, females; Q, quartile/quintile; PA, physical activity.
*
Exposure dose means the cut-off points or distribution for the highest and lowest categories of blood vitamin B12 level.
†
The quality of the included studies was assessed with the nine-star Newcastle–Ottawa Scale criteria.