Table 2. Hazard ratios (HR) of overall cancer and 95% confidence intervals (95% CI) by quartiles (Q) of red blood cell (RBC) folate, serum folate, and dietary folate equivalents (DFE) 1,2, NHANES 1999–2002.
| Q1 | Q2 | Q3 | Q4 | |
|---|---|---|---|---|
| Red blood cell folate (ng/ml) | <237.8 | 237.8–<318.0 | 318.0–<422.0 | ≥422.0 |
| Sample size, n | 341 | 361 | 350 | 350 |
| All-cancer cases, n (%) | 38 (11.1) | 39 (10.3) | 27 (7.7) | 20 (5.7) |
| HR, adjusted (95% CI) | 0.98 (0.61–1.57) | 1.0 | 0.68 (0.41–1.14) | 0.54 (0.31–0.93) |
| Serum folate (ng/ml) | <10.7 | 10.7–<15.6 | 15.6–<22.9 | ≥22.9 |
| Sample size, n | 334 | 350 | 355 | 345 |
| All-cancer cases n (%) | 42 (12.6) | 32 (9.1) | 30 (8.4) | 19 (5.5) |
| HR, adjusted (95% CI) | 1.44 (0.90–2.31) | 1.0 | 0.88 (0.53–1.47) | 0.59 (0.33–1.05) |
| DFE (μg/d) | <291.6 | 291.6–<467.0 | 467.0–<836.4 | ≥836.4 |
| Sample size, n | 345 | 353 | 351 | 338 |
| All-cancer cases n (%) | 31 (9.0) | 38 (10.8) | 38 (10.8) | 18 (5.3) |
| HR adjusted, (95% CI) | 0.85 (0.51–1.41) | 1.0 | 0.95 (0.60–1.52) | 0.54 (0.30–0.95) |
1 Tests were performed using Cox proportional hazards regression models that included log-transformed RBC folate, serum folate or DFE
2 Models were adjusted for age, gender, race/ethnicity, educational attainment, smoking status, alcohol intake, physical activity, and BMI. The DFE model was additionally adjusted for total energy intake.