Table 1.
Participant characteristics by study and case-control status
| Study | Case–control status | Participants, N | Age at blood collection, yr, mean (SD) | Date of blood collection, minimum-maximum | BMI, kg/m2, mean (SD) | Higher education, % | Current smokers, % | Geometric mean (95% CI) |
|
|---|---|---|---|---|---|---|---|---|---|
| Folate, nmol/l |
Vitamin B12, pmol/l | ||||||||
| ATBC | Case | 224 | 60.9 (5.0) | 1985–1988 | 26.4 (3.5) | 3.6 | 100.0 | 8.6 (8.2–9.0) | 344 (328–360) |
| Control | 440 | 60.7 (4.8) | 1985–1988 | 25.9 (3.6) | 5.5 | 100.0 | 8.5 (8.2–8.8) | 342 (330–355) | |
| CARET | Case | 389 | 62.3 (5.7) | 1985–1997 | 28.5 (4.3) | 24.3 | 52.2 | 15.3 (14.3–16.5) | 299 (288–311) |
| Control | 773 | 62.1 (5.8) | 1985–1996 | 28.3 (4.5) | 23.0 | 52.1 | 15.5 (14.7–16.3) | 307 (298–316) | |
| EPIC | Case | 1244 | 60.0 (6.6) | 1989–2003 | 26.8 (3.4) | 25.4 | 20.9 | 13.8 (13.3–14.3) | 332 (324–340) |
| Control | 1341 | 59.8 (6.6) | 1989–2003 | 26.8 (3.6) | 22.6 | 23.3 | 12.7 (12.3–13.2) | 327 (321–334) | |
| Janus | Case | 3000 | 48.7 (8.8) | 1981–2002 | 25.6 (3.0) | NA | 39.4 | 14.1 (14.0–14.3) | 451 (445–458) |
| Control | 3000 | 48.6 (8.7) | 1981–2002 | 25.7 (3.1) | NA | 39.7 | 13.9 (13.8–14.1) | 444 (438–450) | |
| NSHDC | Case | 560 | 56.6 (5.2) | 1986–2004 | 26.0 (3.1) | 13.4 | 28.9 | 5.9 (5.7–6.2) | 334 (326–342) |
| Control | 1044 | 56.5 (5.2) | 1986–2004 | 26.2 (3.5) | 13.0 | 25.1 | 5.7 (5.5–5.9) | 320 (313–328) | |
| ProtecT | Case | 1458 | 62.0 (5.1) | 2003–2008 | 26.7 (3.4) | NA | 14.3 | 16.5 (15.9–17.0) | 301 (295–307) |
| Control | 1506 | 61.8 (5.1) | 2003–2008 | 26.9 (3.8) | NA | 12.5 | 16.9 (16.4–17.5) | 295 (289–300) | |
ATBC = Alpha-Tocopherol, Beta-Carotene Cancer Prevention Study; BMI = body mass index; CARET = Carotene and Retinol Efficacy Trial; CI = confidence interval; EPIC = European Prospective Investigation into Cancer and Nutrition; NA = data not available; NSHDC = Northern Sweden Health and Disease Study cohort; ProtecT = Prostate Testing for Cancer and Treatment Trial; SD = standard deviation.
The numbers of cases and controls are the maximum number for whom folate and vitamin B12 measurements were available.