TABLE 4.
Nitrate, nitrite, nitrosodimethylamine (NDMA), and nitrosopyrolidine (NPYR) intakes and the risk of glioma in the Health Professionals Follow-Up Study (HPFS; 1986–2004), Nurses’ Health Study I (NHS I; 1980–2004), and NHS II (1991–2005)
| Quintile of intake |
||||||
| 1 | 2 | 3 | 4 | 5 | P for trend1 | |
| Nitrate2 | ||||||
| Cases | 67 | 74 | 60 | 59 | 75 | |
| Person-years | 815,155 | 833,168 | 811,541 | 822,304 | 818,945 | |
| RR (95% CI)3 | 1.0 | 1.06 (0.76, 1.48) | 0.84 (0.57, 1.22) | 0.95 (0.46, 1.98) | 1.02 (0.66, 1.58) | 0.81 |
| Nitrite2 | ||||||
| Cases | 55 | 65 | 71 | 69 | 75 | |
| Person-years | 812,763 | 812,974 | 844,064 | 810,417 | 820,895 | |
| RR (95% CI)3 | 1.0 | 1.11 (0.72, 1.71) | 1.20 (0.84, 1.71) | 1.14 (0.73, 1.78) | 1.26 (0.89, 1.79) | 0.23 |
| NDMA2 | ||||||
| Cases | 69 | 80 | 59 | 67 | 60 | |
| Person-years | 794,817 | 1,012,119 | 672,847 | 888,972 | 732,359 | |
| RR (95% CI)3 | 1.0 | 0.95 (0.68, 1.33) | 0.91 (0.64, 1.30) | 0.94 (0.66, 1.32) | 0.88 (0.57, 1.36) | 0.73 |
| NPYR4 | ||||||
| Cases | 193 | 58 | 84 | |||
| Person-years | 2,244,720 | 968,505 | 887,888 | |||
| RR (95% CI)3 | 1.0 | 0.81 (0.52, 1.20) | 0.81 (0.62, 1.05) | 0.93 | ||
Based on the median value of each intake category and modeling these as continuous variables in a Cox proportional hazards model.
Cutoffs for quintiles were different for each cohort and are based on baseline values: nitrate (HPFS: 87, 120, 155, and 205; NHS I: 43, 56, 87, and 145; NHS II: 78, 108, 141, and 190), nitrite (HPFS: 1.4, 1.6, 1.8, and 2.0; NHS I: 1.1, 1.3, 1.5, and 1.7; NHS II: 1.7, 1.9, 2.1, and 2.4), and NDMA (HPFS: 0.04, 0.05, 0.07, and 0.09; NHS I: 0.02, 0.04, 0.05, and 0.09; NHS II: 0.04, 0.05, 0.06, and 0.08).
Rate ratios (RRs) and 95% CIs from Cox proportional hazards models were adjusted for age and caloric intake (quintiles). Results were obtained from pooling the β coefficient and SE estimates by using the DerSimonian and Laird random-effects model; no significant evidence of heterogeneity by cohort was observed (α = 0.05).
Because of the limited range of intakes, it was not possible to create quintiles. Cutoffs are for the following tertiles: HPFS (0.01 and 0.03), NHS I (0.01 and 0.02), and NHS II (0.01 and 0.02).