Table 3.
Quintiles of nondairy animal protein intake and risk of kidney stones
| Cohort | Quintile 1 | Quintile 2 | Quintile 3 | Quintile 4 | Quintile 5 | P Value for Trend |
|---|---|---|---|---|---|---|
| HPFS | ||||||
| Median, g/d | 31.4 | 42.6 | 50.3 | 58.6 | 72.5 | 0.004 |
| Range | <38.9 | 38.9–47.2 | 47.3–55.4 | 55.5–66.2 | >66.2 | 0.04 |
| Patients | 351 | 364 | 379 | 424 | 445 | |
| Person-time | 133,204 | 133,448 | 134,142 | 134,288 | 134,406 | |
| Age-adjusted HR (95% CI) | 1.00 (reference) | 1.04 (0.90 to 1.20) | 1.05 (0.91 to 1.22) | 1.17 (1.01 to 1.35) | 1.19 (1.04 to 1.37) | |
| Multivariate-adjusted HR (95% CI) | 1.00 (reference) | 0.98 (0.84 to 1.14) | 0.99 (0.85 to 1.15) | 1.09 (0.93 to 1.28) | 1.15 (0.97 to 1.36) | |
| NHS I | ||||||
| Median, g/d | 30.9 | 39.6 | 45.9 | 52.8 | 64.4 | 0.001 |
| Range | <36.2 | 36.2–42.9 | 43.0–49.5 | 49.6–58.1 | >58.1 | 0.06 |
| Patients | 229 | 253 | 259 | 268 | 322 | |
| Person-time | 202,112 | 203,103 | 203,627 | 202,284 | 199,316 | |
| Age-adjusted HR (95% CI) | 1.00 (reference) | 1.10 (0.92 to 1.31) | 1.09 (0.91 to 1.30) | 1.12 (0.94 to 1.34) | 1.34 (1.13 to 1.59) | |
| Multivariate-adjusted HR (95% CI) | 1.00 (reference) | 1.04 (0.87 to 1.25) | 1.02 (0.84 to 1.22) | 1.03 (0.85 to 1.25) | 1.20 (0.99 to 1.46) | |
| NHS II | ||||||
| Median, g/d | 30.9 | 41.3 | 48.3 | 55.8 | 68.5 | 0.01 |
| Range | <37.3 | 37.3–45.1 | 45.2–52.7 | 52.8–62.7 | >62.7 | 0.64 |
| Patients | 560 | 645 | 566 | 576 | 667 | |
| Person-time | 286,109 | 286,994 | 286,767 | 285,358 | 282,807 | |
| Age-adjusted HR (95% CI) | 1.00 (reference) | 1.14 (1.02 to 1.28) | 1.01 (0.90 to 1.13) | 1.03 (0.92 to 1.16) | 1.21 (1.09 to 1.36) | |
| Multivariate-adjusted HR (95% CI) | 1.00 (reference) | 1.07 (0.95 to 1.20) | 0.91 (0.80 to 1.03) | 0.91 (0.80 to 1.03) | 1.02 (0.90 to 1.17) | |
| Pooled cohorts | ||||||
| Age-adjusted HR (95% CI) | 1.00 (reference) | 1.10 (1.02 to 1.19) | 1.04 (0.96 to 1.12) | 1.09 (1.00 to 1.18) | 1.23 (1.14 to 1.33) | <0.001 |
| Multivariate-adjusted HR (95% CI) | 1.00 (reference) | 1.04 (0.95 to 1.12) | 0.95 (0.88 to 1.04) | 1.00 (0.89 to 1.12) | 1.10 (1.00 to 1.21) | 0.20 |
Multivariate models were adjusted for age, body mass index, history of diabetes, history of hypertension, use of thiazides, supplemental calcium, and intakes of fluid, sodium, potassium, fructose, oxalate, phytate, alcohol, and all other types of protein. Medians refer to the first time period; however, dietary variables were updated over the course of the study. HPFS, Health Professionals Follow-Up Study; HR, hazard ratio; 95% CI, 95% confidence interval; NHS I, Nurses’ Health Study I; NHS II, Nurses’ Health Study II.