Table 4.
Association between dietary nitrate and nitrite and bladder cancer in the Iowa Women’s Health Study (N = 33,964a).
| Nitrate/nitrite sources | Cases | n | Age-adjusted HR (95% CI) | Fully adjustedb HR (95% CI) |
|---|---|---|---|---|
| Dietary nitrate (mg NO3-N/dayc) | ||||
| All sources | ||||
| < 16.2 | 67 | 8,467 | 1.00 (Reference) | 1.00 (Reference) |
| 16.2–23.9 | 68 | 8,489 | 1.00 (0.72, 1.41) | 1.01 (0.72, 1.43) |
| 24.0–34.2 | 64 | 8,506 | 0.92 (0.66, 1.30) | 0.94 (0.66, 1.35) |
| > 34.2 | 59 | 8,502 | 0.86 (0.60, 1.22) | 0.85 (0.58, 1.26) |
| ptrendd | 0.32 | 0.34 | ||
| Continuouse | 258 | 33,964 | 0.85 (0.69, 1.04) | 0.83 (0.65, 1.05) |
| Dietary nitrite (mg/day) | ||||
| All sources | ||||
| < 0.86 | 63 | 8,450 | 1.00 (Reference) | 1.00 (Reference) |
| 0.86–1.12 | 66 | 8,514 | 1.01 (0.71, 1.42) | 1.15 (0.78, 1.70) |
| 1.13–1.43 | 73 | 8,487 | 1.12 (0.80, 1.56) | 1.38 (0.89, 2.16) |
| > 1.43 | 56 | 8,513 | 0.85 (0.60, 1.22) | 1.15 (0.65, 2.03) |
| ptrend | 0.44 | 0.69 | ||
| Continuous | 258 | 33,964 | 0.95 (0.70, 1.29) | 1.59 (0.89, 2.84) |
| Plant sources | ||||
| < 0.51 | 62 | 8,461 | 1.00 (Reference) | 1.00 (Reference) |
| 0.51–0.67 | 75 | 8,507 | 1.17 (0.84, 1.64) | 1.33 (0.92, 1.91) |
| 0.68–0.90 | 69 | 8,490 | 1.08 (0.76, 1.52) | 1.32 (0.88, 1.99) |
| > 0.90 | 52 | 8,506 | 0.81 (0.56, 1.17) | 1.05 (0.64, 1.72) |
| ptrend | 0.15 | 0.82 | ||
| Continuous | 258 | 33,964 | 0.86 (0.66, 1.12) | 1.10 (0.74, 1.63) |
| Animal sources | ||||
| < 0.29 | 67 | 8,474 | 1.00 (Reference) | 1.00 (Reference) |
| 0.29–0.40 | 54 | 8,443 | 0.79 (0.55, 1.14) | 0.86 (0.59, 1.25) |
| 0.41–0.56 | 64 | 8,533 | 0.92 (0.66, 1.30) | 1.03 (0.70, 1.53) |
| > 0.56 | 73 | 8,514 | 1.06 (0.76, 1.47) | 1.24 (0.79, 1.95) |
| ptrend | 0.53 | 0.22 | ||
| Continuous | 258 | 33,964 | 1.10 (0.86, 1.39) | 1.31 (0.93, 1.86) |
| Processed meats | ||||
| < 0.01 | 69 | 8,718 | 1.00 (Reference) | 1.00 (Reference) |
| 0.01–0.03 | 75 | 8,707 | 1.00 (0.72, 1.40) | 0.95 (0.68, 1.33) |
| 0.04–0.06 | 54 | 8,107 | 0.89 (0.63, 1.26) | 0.86 (0.60, 1.22) |
| > 0.06 | 60 | 8,432 | 0.95 (0.67, 1.33) | 0.88 (0.61, 1.26) |
| ptrend | 0.68 | 0.46 | ||
| Continuous | 258 | 33,964 | 0.99 (0.95, 1.02) | 0.98 (0.94, 1.02) |
| Abbreviations: CI, confidence interval; HR, hazard ratio. aAfter excluding 744 women with missing covariate data. bAdjusted for age, smoking status, pack-years of smoking, and ln-transformed total energy intake. Nitrate models were also adjusted for total ln-transformed dietary nitrite from all sources, and nitrite models were adjusted for total ln-transformed dietary nitrate from all sources. cNO3– converted to NO3-N. Nitrate intakes came almost exclusively from plant sources. dEstimated by modeling a continuous variable derived from the median value within each exposure category. eHR per 1 natural log increase in intake (milligrams/day). | ||||