TABLE 1.
Baseline characteristics of the WHI Observational Study participants by quintile of total magnesium intake1
| <206.5 mg | 206.5–270.2 mg | 270.3–333.7 mg | 333.8–422.4 mg | ≥422.5 mg | P | |
| Age [n (Ann %)] | <0.001 | |||||
| 50–59 y | 4923 (33.9) | 4825 (32.7) | 4848 (32.6) | 4737 (31.6) | 4987 (33.5) | |
| 60–69 y | 6191 (42.6) | 6400 (43.3) | 6441 (43.4) | 6656 (44.4) | 6592 (44.3) | |
| 70–79 y | 3426 (23.6) | 3544 (24.0) | 3560 (24.0) | 3607 (24.0) | 3294 (22.1) | |
| Race-ethnicity [n (Ann %)] | <0.001 | |||||
| White | 10,877 (74.8) | 12,419 (84.1) | 12,999 (87.5) | 13,464 (89.8) | 13,326 (89.6) | |
| Black | 1888 (13.0) | 1074 (7.3) | 802 (5.4) | 668 (4.5) | 601 (4.0) | |
| Hispanic | 821 (5.6) | 577 (3.9) | 425 (2.9) | 360 (2.4) | 344 (2.3) | |
| American Indian | 82 (0.6) | 61 (0.4) | 47 (0.3) | 34 (0.2) | 49 (0.3) | |
| Asian/Pacific Islander | 630 (4.3) | 447 (3.0) | 410 (2.8) | 319 (2.1) | 356 (2.4) | |
| Unknown | 242 (1.7) | 191 (1.3) | 166 (1.1) | 155 (1.0) | 197 (1.3) | |
| Parental history of fracture [n (Ann %)] | 5353 (36.8) | 5772 (39.1) | 5890 (39.7) | 6186 (41.2) | 6184 (41.6) | <0.001 |
| Fracture at ≥55 y of age [n (Ann %)] | 1919 (13.2) | 2170 (14.7) | 2156 (14.5) | 2223 (14.8) | 2299 (15.5) | <0.001 |
| BMI [n (Ann %)] | <0.001 | |||||
| <25 kg/m2 | 5545 (38.1) | 6102 (41.3) | 6268 (42.2) | 6359 (42.4) | 6483 (43.6) | |
| ≥25 kg/m2 | 8995 (61.9) | 8667 (58.7) | 8581 (57.8) | 8641 (57.6) | 8390 (56.4) | |
| History of MI or angina [n (Ann %)] | 1076 (7.4) | 1018 (6.9) | 888 (6.0) | 943 (6.3) | 928 (6.2) | <0.001 |
| Treated diabetes [n (Ann %)] | 699 (4.8) | 599 (4.1) | 528 (3.6) | 542 (3.6) | 486 (3.3) | <0.001 |
| Self-reported health [n (Ann %)] | <0.001 | |||||
| Excellent | 2260 (15.5) | 2719 (18.4) | 2875 (19.4) | 2906 (19.4) | 3017 (20.3) | |
| Very good | 5537 (38.1) | 5975 (40.5) | 6294 (42.4) | 6482 (43.2) | 6385 (42.9) | |
| Good | 4993 (34.3) | 4765 (32.3) | 4504 (30.3) | 4475 (29.8) | 4370 (29.4) | |
| Fair/poor | 1750 (12.0) | 1310 (8.9) | 1176 (7.9) | 1137 (7.6) | 1101 (7.4) | |
| HT use [n (Ann %)] | <0.001 | |||||
| Never/past user | 9704 (66.7) | 9494 (64.3) | 9474 (63.8) | 9522 (63.5) | 9403 (63.2) | |
| <5 y | 1748 (12.0) | 1925 (13.0) | 1945 (13.1) | 1897 (12.6) | 1974 (13.3) | |
| 5 to <10 y | 1262 (8.7) | 1359 (9.2) | 1471 (9.9) | 1533 (10.2) | 1516 (10.2) | |
| 10 to <15 y | 776 (5.3) | 885 (6.0) | 880 (5.9) | 967 (6.4) | 929 (6.2) | |
| ≥15 y | 1050 (7.2) | 1106 (7.5) | 1079 (7.3) | 1081 (7.2) | 1051 (7.1) | |
| Thiazide use [n (Ann %)] | <0.001 | |||||
| Nonuser | 13,689 (94.1) | 13,983 (94.7) | 14,059 (94.7) | 14,249 (95.0) | 14,185 (95.4) | |
| <10 y | 616 (4.2) | 566 (3.8) | 532 (3.6) | 514 (3.4) | 480 (3.2) | |
| ≥10 y | 235 (1.6) | 220 (1.5) | 258 (1.7) | 236 (1.6) | 208 (1.4) | |
| Current corticosteroid use [n (Ann %)] | 208 (1.4) | 207 (1.4) | 184 (1.2) | 187 (1.2) | 181 (1.2) | 0.380 |
| Alcohol intake [n (Ann %)] | <0.001 | |||||
| Nondrinker | 2088 (14.4) | 1649 (11.2) | 1556 (10.5) | 1406 (9.4) | 1350 (9.1) | |
| Past drinker | 3026 (20.8) | 2682 (18.2) | 2503 (16.9) | 2481 (16.5) | 2722 (18.3) | |
| <1 drink/mo | 1879 (12.9) | 1825 (12.4) | 1667 (11.2) | 1566 (10.4) | 1626 (10.9) | |
| <1 drink/wk | 2922 (20.1) | 2920 (19.8) | 3034 (20.4) | 3023 (20.2) | 2999 (20.2) | |
| 1 to <7 drinks/wk | 3231 (22.2) | 3872 (26.2) | 4040 (27.2) | 4269 (28.5) | 4128 (27.8) | |
| ≥7 drinks/wk | 1394 (9.6) | 1821 (12.3) | 2049 (13.8) | 2255 (15.0) | 2048 (13.8) | |
| Smoking status [n (Ann %)] | <0.001 | |||||
| Never | 7449 (51.2) | 7571 (51.3) | 7570 (51.0) | 7649 (51.0) | 7617 (51.2) | |
| Past | 5758 (39.6) | 6211 (42.1) | 6477 (43.6) | 6631 (44.2) | 6719 (45.2) | |
| Current | 1333 (9.2) | 987 (6.7) | 802 (5.4) | 720 (4.8) | 537 (3.6) | |
| Total daily calcium intake [n (Ann %)]2 | <0.001 | |||||
| <600 mg | 8233 (56.6) | 3331 (22.6) | 1168 (7.9) | 323 (2.2) | 125 (0.8) | |
| 600–1500 mg | 5283 (36.3) | 9325 (63.1) | 10,029 (67.5) | 8814 (58.8) | 4879 (32.8) | |
| >1500 mg | 1024 (7.0) | 2113 (14.3) | 3652 (24.6) | 5863 (39.1) | 9869 (66.4) | |
| Total daily vitamin D intake [n (Ann %)]2 | <0.001 | |||||
| <200 IU | 11,303 (77.7) | 7205 (48.8) | 3898 (26.3) | 1974 (13.2) | 1460 (9.8) | |
| 200–500 IU | 2516 (17.3) | 5253 (35.6) | 5804 (39.1) | 4778 (31.9) | 3435 (23.1) | |
| >500 IU | 721 (5.0) | 2311 (15.6) | 5147 (34.7) | 8248 (55.0) | 9978 (67.1) | |
| Physical activity [n (Ann %)] | <0.001 | |||||
| Inactive | 2863 (19.7) | 2146 (14.5) | 1795 (12.1) | 1558 (10.4) | 1385 (9.3) | |
| <5 METs/wk | 3460 (23.8) | 2956 (20.0) | 2759 (18.6) | 2573 (17.2) | 2191 (14.7) | |
| 5–12 METs/wk | 3349 (23.0) | 3667 (24.8) | 3592 (24.2) | 3609 (24.1) | 3339 (22.5) | |
| >12 METs/wk | 4792 (33.0) | 5918 (40.1) | 6602 (44.5) | 7155 (47.7) | 7860 (52.8) | |
| Time spent walking [n (Ann %)] | <0.001 | |||||
| 0 min/wk | 7250 (49.9) | 6289 (42.6) | 5628 (37.9) | 5385 (35.9) | 4951 (33.3) | |
| >0–150 min/wk | 5423 (37.3) | 6237 (42.2) | 6702 (45.1) | 6989 (46.6) | 6905 (46.4) | |
| >150 min/wk | 1867 (12.8) | 2243 (15.2) | 2519 (17.0) | 2626 (17.5) | 3017 (20.3) | |
| Family income [n (Ann %)] | <0.001 | |||||
| <$10,000 | 818 (5.6) | 538 (3.6) | 421 (2.8) | 382 (2.5) | 422 (2.8) | |
| $10,000–$19,999 | 1866 (12.8) | 1515 (10.3) | 1356 (9.1) | 1357 (9.0) | 1312 (8.8) | |
| $20,000–$34,999 | 3316 (22.8) | 3234 (21.9) | 3128 (21.1) | 3155 (21.0) | 3045 (20.5) | |
| $35,000–$49,999 | 2606 (17.9) | 2762 (18.7) | 2857 (19.2) | 2900 (19.3) | 2915 (19.6) | |
| $50,000–$74,999 | 2435 (16.7) | 2760 (18.7) | 2970 (20.0) | 2946 (19.6) | 3098 (20.8) | |
| ≥$75,000 | 2354 (16.2) | 2906 (19.7) | 3112 (21.0) | 3166 (21.1) | 3142 (21.1) | |
| US region [n (Ann %)] | <0.001 | |||||
| Northeast | 3381 (23.3) | 3573 (24.2) | 3597 (24.2) | 3574 (23.8) | 3290 (22.1) | |
| South | 4298 (29.6) | 3816 (25.8) | 3700 (24.9) | 3559 (23.7) | 3257 (21.9) | |
| Midwest | 2877 (19.8) | 3269 (22.1) | 3444 (23.2) | 3776 (25.2) | 3376 (22.7) | |
| West | 3984 (27.4) | 4111 (27.8) | 4108 (27.7) | 4091 (27.3) | 4950 (33.3) |
1
All variables were assessed at the baseline screening visit. Magnesium values include the combined intake from food and supplements (range: 0.38–9274 mg/d; 99th percentile: 958 mg/d). P values were based on significant differences between all quintiles. Ann, annual; HT, hormone therapy; MET, metabolic equivalent task; MI, myocardial infarction; WHI, Women's Health Initiative.
2
Calcium and vitamin D values include the combined intake from food and supplements.