Table 1.
Characteristics of cohort studies included in the pooled analysis of folate intake and colon cancer risk
| Follow-up period | Baseline cohort (n)e | Colon cancer cases (n) | Prevalence of multivitamin use (%) | Median (10th–90th percentile) intake |
||
|---|---|---|---|---|---|---|
| Folate from foods (μg/day)a | Folate from foods and supplements (μg/day)a | |||||
| Alpha-Tocopherol Beta-Carotene Cancer Prevention Study | 1985–1999 | 26,987 | 187 | 8 | 256 (206–314) | 259 (207–329) |
| Breast Cancer Detection Demonstration Project Follow-up Cohort | 1987–1998 | 41,987 | 349 | 33 | 301 (183–502) | 381 (200–835) |
| Canadian National Breast Screening Studyb | 1980–2000 | 49,654 | 431 | – | 244 (169–343) | – |
| Cancer Prevention Study II Nutrition Cohort (men) | 1992–1998 | 66,071 | 467 | 33 | 309 (198–447) | 363 (212–777) |
| Cancer Prevention Study II Nutrition Cohort (women) | 1992–1999 | 74,046 | 349 | 42 | 271 (164–436) | 371 (181–779) |
| Health Professionals Follow-up Study | 1986–2000 | 47,766 | 456 | 43 | 353 (242–514) | 404 (255–827) |
| Iowa Women’s Health Study | 1986–2001 | 34,588 | 799 | 33 | 248 (169–364) | 281 (178–679) |
| Netherlands Cohort Study (men)c | 1986–1993 | 58,279 | 393 | 3 | 210 (158–295) | – |
| Netherlands Cohort Study (women)c | 1986–1993 | 62,573 | 353 | 6 | 184 (137–261) | – |
| New York State Cohort (men) | 1980–1987 | 30,363 | 335 | 38 | 409 (290–603) | 496 (307–874) |
| New York State Cohort (women) | 1980–1987 | 22,550 | 223 | 49 | 378 (263–552) | 501 (289–861) |
| New York University Women’s Health Study | 1985–1998 | 13,258 | 96 | 50 | 270 (155–453) | 447 (183–770) |
| Nurses’ Health Study (a) | 1980–1986 | 88,651 | 162 | 34 | 240 (151–379) | 277 (159–667) |
| Nurses’ Health Study (b) | 1986–2000 | 68,502d | 429 | 43 | 274 (190–397) | 322 (202–709) |
| Prospective Study on Hormones, Diet and Breast Cancer (ORDET)b | 1987–2001 | 9,027 | 43 | – | 259 (201–342) | – |
| Swedish Mammography Cohortb | 1987–2003 | 60,950 | 485 | – | 218 (170–277) | – |
| Women’s Health Study | 1993–2003 | 38,384 | 163 | 32 | 287 (201–409) | 327 (211–706) |
| Total | 725,134 | 5,720 | ||||
Calorie-adjusted median (10th–90th percentile) intake among baseline cohort or subcohort for the Canadian National Breast Screening Study and the Netherlands Cohort Study, adjusted to 2,100 kcal/day for men and 1,600 kcal/day for women
Information on supplementary folate intake was not available at baseline for this study
Folate was not contained in multivitamin supplements at the time of the baseline questionnaire for this study
These women are a subset of the women included in Nurses’ Health Study (a) and are not included in the total baseline cohort size
Cohort sizes after applying study-specific exclusion criteria and then excluding participants with loge-transformed energy intake values beyond three standard deviations from the study-specific mean and previous cancer diagnoses (other than nonmelanoma skin cancer); the Canadian National Breast Screening Study and the Netherlands Cohort Study are analyzed as case-cohort studies so their baseline cohort sizes do not reflect the above exclusions