TABLE 1.
Baseline characteristic of participants according to calcium (Ca) quartiles groups.
| Characteristics | Calcium (mg/day) | |||||
| Total | Q1h | Q2i | Q3j | Q4k | P-value | |
| (n = 14,971) | (n = 3,576) | (n = 3,692) | (n = 3,846) | (n = 3,857) | ||
| Calcium (mg/day) | ≤534 | (535–817) | (818–1,190) | ≥1,191 | ||
| Age, median (IQRa) | 46.0 (32.0, 61.0) | 49.0 (34.0, 63.0) | 47.0 (33.0, 62.0) | 46.0 (32.0, 60.0) | 42.0 (30.0, 56.0) | <0.001* |
| Sex [n (%)] | <0.001* | |||||
| Male | 7,817 (52.2) | 1,603 (44.8) | 1,788 (48.4) | 1,975 (51.4) | 2,451 (63.5) | |
| Female | 7,154 (47.8) | 1,973 (55.2) | 1,904 (51.6) | 1,871 (48.6) | 1,406 (36.5) | |
| Marital status [n (%)] | <0.001* | |||||
| Married | 7,742 (51.7) | 1,703 (47.6) | 1,936 (52.4) | 2,041 (53.1) | 2,062 (53.5) | |
| Widowed | 847 (5.7) | 276 (7.7) | 208 (5.6) | 217 (5.6) | 146 (3.8) | |
| Divorced | 1,624 (10.8) | 452 (12.6) | 418 (11.3) | 400 (10.4) | 354 (9.2) | |
| Separated | 458 (3.1) | 129 (3.6) | 111 (3) | 117 (3) | 101 (2.6) | |
| Never married | 2,997 (20.0) | 716 (20) | 710 (19.2) | 761 (19.8) | 810 (21) | |
| Living with partner | 1,303 (8.7) | 300 (8.4) | 309 (8.4) | 310 (8.1) | 384 (10) | |
| Education [n (%)] | <0.001* | |||||
| Below high school | 2,958 (19.8) | 882 (24.7) | 715 (19.4) | 690 (17.9) | 671 (17.4) | |
| High school grad/GEDb/equivalent | 3,315 (22.1) | 881 (24.6) | 807 (21.9) | 817 (21.2) | 810 (21) | |
| Above high school | 8,698 (58.1) | 1,813 (50.7) | 2,170 (58.8) | 2,339 (60.8) | 2,376 (61.6) | |
| Race/Ethnicity [n (%)] | <0.001* | |||||
| Mexican American | 2,108 (14.1) | 423 (11.8) | 517 (14) | 555 (14.4) | 613 (15.9) | |
| Other Hispanic | 1,466 (9.8) | 364 (10.2) | 356 (9.6) | 379 (9.9) | 367 (9.5) | |
| Non-Hispanic white | 6,942 (46.4) | 1,362 (38.1) | 1,678 (45.4) | 1,841 (47.9) | 2,061 (53.4) | |
| Non-Hispanic black | 2,911 (19.4) | 981 (27.4) | 720 (19.5) | 694 (18) | 516 (13.4) | |
| Other races | 1,544 (10.3) | 446 (12.5) | 421 (11.4) | 377 (9.8) | 3,080 (7.8) | |
| BMIc [n (%)] | 0.578 | |||||
| Under weight | 221 (1.5) | 58 (1.6) | 62 (1.7) | 52 (1.4) | 49 (1.3) | |
| Normal weight | 4,317 (28.8) | 1,014 (28.4) | 1,053 (28.5) | 1,154 (30) | 1,096 (28.4) | |
| Over weight | 5,040 (33.7) | 1,188 (33.2) | 1,257 (34) | 1,274 (33.1) | 1,321 (34.2) | |
| Obese | 5,393 (36.0) | 1,316 (36.8) | 1,320 (35.8) | 1,366 (35.5) | 1,391 (36.1) | |
| PIRd [n (%)] | <0.001* | |||||
| Poor | 3,007 (20.1) | 831 (23.2) | 723 (19.6) | 693 (18) | 760 (19.7) | |
| Near poor | 3,777 (25.2) | 967 (27) | 929 (25.2) | 934 (24.3) | 947 (24.6) | |
| Middle-income | 3,958 (26.4) | 949 (26.5) | 978 (26.5) | 1,055 (27.4) | 976 (25.3) | |
| High-income | 4,229 (28.2) | 829 (23.2) | 1,062 (28.8) | 1,164 (30.3) | 1,174 (30.4) | |
| Smoking status [n (%)] | <0.001* | |||||
| Never | 8,323 (55.6) | 1,890 (52.9) | 2,055 (55.7) | 2,212 (57.5) | 2,166 (56.2) | |
| Former | 3,582 (23.9) | 821 (23) | 916 (24.8) | 945 (24.6) | 900 (23.3) | |
| Now | 3,066 (20.5) | 865 (24.2) | 721 (19.5) | 689 (17.9) | 791 (20.5) | |
| Alcohol drinking [n (%)] | <0.001* | |||||
| No | 3,653 (24.4) | 1,047 (29.3) | 929 (25.2) | 908 (23.6) | 769 (19.9) | |
| Yes | 11,318 (75.6) | 2,529 (70.7) | 2,763 (74.8) | 2,938 (76.4) | 3,088 (80.1) | |
| Carbohydrates (Mean ± SDe) | 258.3 ± 122.5 | 186.2 ± 90.0 | 231.8 ± 94.8 | 267.3 ± 105.6 | 341.6 ± 136.0 | <0.001* |
| Caffeine intake [Median (IQR)] | 101.0 (15.0, 216.0) | 91.0 (11.0, 198.0) | 100.0 (20.0, 205.0) | 101.0 (13.0, 216.0) | 111.0 (18.0, 248.0) | <0.001* |
| Total energy intake (Mean ± SD) | 2,148.8 ± 956.0 | 1,509.3 ± 645.2 | 1,923.9 ± 716.1 | 2,226.2 ± 790.1 | 2,879.9 ± 1,039.5 | <0.001* |
| Calcium supplement [Median (IQR)] | 315.0 (200.0, 600.0) | 400.0 (210.0, 667.0) | 383.0 (200.0, 627.5) | 326.0 (200.0, 609.0) | 238.0 (200.0, 600.0) | <0.001* |
| Serum vitamins D [n (%)] | <0.001* | |||||
| <50 nmol/L | 4,521 (30.2) | 1,336 (37.4) | 1,134 (30.7) | 1,108 (28.8) | 943 (24.4) | |
| 50–74 nmol/L | 5,612 (37.5) | 1,269 (35.5) | 1,343 (36.4) | 1,430 (37.2) | 1,570 (40.7) | |
| ≥75 nmol/L | 4,838 (32.3) | 971 (27.2) | 1,215 (32.9) | 1,308 (34.0) | 1,344 (34.8) | |
| Serum calcium (mmol/L) [Median (IQR)] | 2.4 (2.3, 2.4) | 2.4 (2.3, 2.4) | 2.4 (2.3, 2.4) | 2.4 (2.3, 2.4) | 2.4 (2.3, 2.4) | <0.001* |
| Depression [n (%)] | <0.001* | |||||
| No | 13,827 (92.4) | 3,220 (90) | 3,419 (92.6) | 3,587 (93.3) | 3,601 (93.4) | |
| Yes | 1,144 (7.6) | 356 (10.0) | 273 (7.4) | 259 (6.7) | 256 (6.6) | |
| Hypertension [n (%)] | <0.001* | |||||
| No | 10,156 (67.8) | 2,270 (63.5) | 2,472 (67.0) | 2,647 (68.8) | 2,767 (71.7) | |
| Yes | 4,815 (32.2) | 1,306 (36.5) | 1,220 (33.0) | 1,199 (31.2) | 1,090 (28.3) | |
| Diabetes [n (%)] | <0.001* | |||||
| No | 1,530 (10.2) | 449 (12.6) | 402 (10.9) | 367 (9.5) | 312 (8.1) | |
| Yes | 13,111 (87.6) | 3,037 (84.9) | 3,212 (87) | 3,396 (88.3) | 3,466 (89.9) | |
| Borderline | 330 (2.2) | 90 (2.5) | 78 (2.1) | 83 (2.2) | 97 (2.0) | |
| CVDf [n (%)] | <0.001* | |||||
| No | 14,028 (93.7) | 3,283 (91.8) | 3,449 (93.4) | 3,615 (94) | 3,681 (95.4) | |
| Yes | 943 (6.3) | 293 (8.2) | 243 (6.6) | 231 (6) | 176 (4.6) | |
| Cancer/malignancy [n (%)] | 0.188 | |||||
| No | 13,644 (91.1) | 3,263 (91.2) | 3,342 (90.5) | 3,495 (90.9) | 3,544 (91.9) | |
| Yes | 1,327 (8.9) | 313 (8.8) | 350 (9.5) | 351 (9.1) | 313 (8.0) | |
| Activity (METg) [Median (IQR)] | 315.0 (200.0, 600.0) | 400.0 (400.0, 667.0) | 383.0 (200.0, 627.5) | 326.0 (200.0, 609.0) | 238.0 (200.0, 600.0) | <0.001* |
IQRa, interquartile range; GEDb, general education development diploma; BMIc, body mass index; PIRd, the ratio of family income to poverty.
SDe, standard deviation; CVDf, severe cardiovascular diseases; METg, metabolic equivalents of task.
Q1h, Ca intake is less than or equal to 534 mg/day.
Q2i, Ca intake ranges from greater than or equal to 535 and less than 817 mg/day.
Q3j, Ca intake ranges from greater than or equal to 818 and less than 1,190 mg/day.
Q4k, Ca intake ranges from greater than or equal to 1,191 mg/day.
*Significant difference among Ca quartiles groups as analyzed by single factor analysis or Kruskal–Wallis test (p < 0.05).