Table 1.
Characteristics of study participants by cohort
| HPFS (n = 1032) | NHS I (n = 1239) | NHS II (n = 1077) | |
|---|---|---|---|
| Age (yr) | 63.4 (58.8–69.3) | 66.2 (61.3–71.5) | 49.6 (45.1–53.8) |
| BMI (kg/m2) | 25.8 (23.7–28.0) | 26.0 (22.9–29.8) | 25.4 (22.5–30.7) |
| History of kidney stones (%) | 62.7 | 69.1 | 62.9 |
| History of hypertension (%) | 35.6 | 49.0 | 22.2 |
| History of diabetes (%) | 5.8 | 9.8 | 4.5 |
| Family history of kidney stones (%) | 18.0 | NA | 25.3 |
| Dietary oxalate (mg/d) | 190 (141–246) | 156 (116–201) | 160 (117–218) |
| Dietary calcium (mg/d) | 769 (627–976) | 733 (572–950) | 824 (661–1071) |
| Supplemental calcium (mg/d) | 0 (0–200) | 401 (0–950) | 200 (0–700) |
| Total vitamin C intake (mg/d) | 239 (148–614) | 203 (135–477) | 165 (108–276) |
| Urinary potassium (mEq/d) | 73 (58–91) | 58 (45–72) | 52 (41–66) |
| Urinary magnesium (mg/d) | 118 (94–147) | 95 (74–122) | 94 (74–121) |
| Urinary phosphate (mg/d) | 1033 (852–1249) | 729 (591–897) | 807 (649–999) |
| Urinary sodium (mEq/d) | 173 (134–224) | 132 (99–172) | 144 (109–182) |
| Urinary creatinine (mg/d) | 1633 (1384–1900) | 1029 (881–1185) | 1168 (1016–1359) |
| Urinary oxalate (mg/d) | 39 (31–47) | 27 (22–33) | 26 (21–32) |
Data are presented as median (25th to 75th percentile) unless otherwise indicated. HPFS, Health Professionals Follow-up Study; NHS, Nurses’ Health Study; BMI, body mass index; NA, not applicable.