Table 1.
Baseline characteristics by oral bisphosphonate use in the WHI study, 1993–2013
| Characteristic at baseline | Oral bisphosphonate use |
|||
|---|---|---|---|---|
| At baseline |
At baseline, year 1, 3 or 6a |
|||
| No | Yes | No | Yes | |
| (n = 148 286) | (n = 3146) | (n = 136 413) | (n = 14 721) | |
| Age at screening (years) (%) | ||||
| <50–59 | 48 681 (32.8) | 406 (12.9)b | 46 242 (33.9) | 2799 (19.0) |
| 60–69 | 66 993 (45.2) | 1462 (46.5) | 60 970 (44.7) | 7326 (49.8) |
| 70–79 | 32 612 (22.0) | 1278 (40.6) | 29 201 (21.4) | 4596 (31.2) |
| Race-ethnicity (%) | ||||
| Non-Hispanic white | 123 276 (83.3) | 2837 (90.3)b | 112 666 (82.8) | 13 186 (89.8) |
| Black/African American | 13 380 (9.1) | 44 (1.4) | 13 026 (9.6) | 376 (2.6) |
| Hispanic/Latino | 5399 (3.7) | 86 (2.7) | 5115 (3.8) | 365 (2.5) |
| American Indian | 632 (0.4) | 1 (0.03) | 607 (0.4) | 26 (0.2) |
| Asian/Pacific islander | 3576 (2.4) | 140 (4.5) | 3126 (2.3) | 585 (4.0) |
| Other/Unknown | 2023 (1.1) | 38 (1.1) | 1873 (1.1) | 183 (1.0) |
| Education (%) | ||||
| High school or less | 33 169 (22.5) | 606 (19.4)b | 30 860 (22.8) | 2843 (19.5) |
| School after high school | 56 154 (38.2) | 1029 (33.0) | 51 963 (38.4) | 5086 (34.8) |
| College degree or higher | 57 880 (39.3) | 1481 (47.5) | 52 606 (38.8) | 6667 (45.7) |
| Missing | 1083 | 30 | 984 | 125 |
| Smoking status (%) | ||||
| Never | 74 302 (50.8) | 1660 (53.6)b | 68 121 (50.6) | 7789 (53.6) |
| Former smoker | 62 063 (42.4) | 1306 (42.1) | 57 202 (42.5) | 6000 (41.3) |
| Current smoker | 10 012 (6.8) | 134 (4.3) | 9330 (6.9) | 742 (5.1) |
| Missing | 1909 | 46 | 1760 | 190 |
| Pack-years of smoking (%) | ||||
| Never | 74 302 (52.0) | 1660 (55.0)b | 68 121 (51.8) | 7789 (54.9) |
| <5 | 20 738 (14.5) | 391 (13.0) | 19 161 (14.6) | 1949 (13.7) |
| 5–20 | 20 662 (14.4) | 413 (13.7) | 19 060 (14.5) | 1983 (14.0) |
| ≥20 | 27 287 (19.1) | 555 (18.4) | 25 186 (19.1) | 2471 (17.4) |
| Missing | 5297 | 127 | 4885 | 529 |
| Physical activity (MET/week) (%) | ||||
| 0–3.00 | 40 623 (28.7) | 692 (22.2)b | 37 712 (29.0) | 3502 (24.5) |
| >3.00–<11.75 | 44 801 (31.7) | 940 (30.1) | 41 126 (31.7) | 4529 (31.6) |
| ≥11.75 | 55 923 (39.6) | 1488 (47.7) | 51 036 (39.3) | 6284 (43.9) |
| Missing | 6939 | 26 | 6539 | 406 |
| Alcohol intake (%) | ||||
| Never | 15 843 (10.8) | 397 (12.7)b | 14 667 (10.8) | 1558 (10.7) |
| Past drinker | 27 776 (18.9) | 541 (17.3) | 25 892 (19.1) | 2366 (16.2) |
| <1 drink per month | 18 331 (12.4) | 287 (9.2) | 16 963 (12.5) | 1612 (11.0) |
| <1 drink per week | 30 217 (20.5) | 675 (21.6) | 27 736 (20.5) | 3102 (21.2) |
| 1–<7 drinks per week | 37 818 (25.7) | 827 (26.5) | 34 444 (25.4) | 4121 (28.2) |
| ≥7 drinks per week | 17 224 (11.7) | 393 (12.6) | 15 714 (11.6) | 1859 (12.7) |
| Missing | 1077 | 26 | 997 | 103 |
| BMI, kg/m2 (%) | ||||
| <25 | 50 435 (34.3) | 1714 (54.9)b | 44 563 (33.0) | 7480 (51.2) |
| 25–30 | 51 162 (34.8) | 1000 (32.0) | 47 212 (34.9) | 4843 (33.2) |
| ≥30 | 45 398 (30.9) | 410 (13.1) | 43 456 (32.1) | 2271 (15.6) |
| Missing | 1291 | 22 | 1182 | 127 |
| Hormone-therapy use (%) | ||||
| Never used | 61 746 (41.6) | 1472 (46.8)b | 55 976 (41.0) | 7099 (48.2) |
| <5 years | 32 788 (22.1) | 702 (22.3) | 30 241 (22.2) | 3195 (21.7) |
| 5 to <10 years | 19 560 (13.2) | 341 (10.8) | 18 214 (13.4) | 1653 (11.2) |
| ≥10 years | 34 187 (23.1) | 631 (20.1) | 31 977 (23.4) | 2774 (18.8) |
| Missing | 2 | 0 | 5 | 0 |
| Statin use (%) | 11 567 (7.8) | 375 (11.9)b | 10 608 (7.8) | 1312 (8.9) |
| History of osteoporosis (%) | 9602 (6.6) | 2251 (72.3)b | 7975 (5.9) | 3849 (26.5) |
| 10-year probability of hip fracture (%) | ||||
| <0.53 | 48 881 (31.6) | 270 (8.6)b | 45 022 (33.0) | 2089 (14.2) |
| 0.53–1.68 | 49 782 (33.6) | 752 (23.9) | 45 867 (33.6) | 4557 (31.0) |
| ≥1.69 | 51 623 (34.8) | 2124 (67.5) | 45 524 (33.4) | 8075 (54.8) |
| Total calcium intake (supplements and diet) (mean ± SD, mg/day) | 1171.8 ± 741.0 | 1585.8 ± 867.5b | 1162.7 ± 741.4 | 1345.2 ± 771.1 |
| Total vitamin D intake (supplements and diet) (mean ± SD, U/day) | 370.7 ± 278.4 | 500.2 ± 314.2b | 367.8 ± 277.6 | 424.8 ± 294.9 |
| WHI study component (%) | ||||
| OS | 84 511 (57.0) | 2312 (73.5) | 79 428 (58.2) | 7285 (49.5) |
| Hormone CT | 25 071 (16.9) | 298 (9.5) | 22 372 (16.4) | 2898 (19.7) |
| Dietary modification CT | 46 076 (31.1) | 585 (18.6) | 41 372 (30.3) | 5181 (35.2) |
| Calcium/vitamin D CT | 34 250 (23.1) | 354 (11.3) | 30 736 (22.5) | 3778 (25.7) |
| Enrollment in WHI hormone CT (%) | ||||
| No | 123 215 (83.1) | 2848 (90.5) | 114 041 (83.6) | 11 823 (80.3) |
| E-alone placebo group | 5067 (3.4) | 53 (1.7) | 4584 (3.4) | 523 (3.6) |
| E-alone active group | 4960 (3.3) | 45 (1.4) | 4562 (3.3) | 418 (2.8) |
| E+P placebo group | 7361 (5.0) | 103 (3.3) | 6317 (4.6) | 1124 (7.6) |
| E+P active group | 7683 (5.2) | 95 (3.0) | 6909 (5.1) | 833 (5.7) |
| Bisphosphonate type (%) | ||||
| Alendronate sodium | – | 2913 (92.6) | – | 13 467 (91.5) |
| Risedronate sodium | – | 13 (0.4) | – | 898 (6.1) |
| Othersc | – | 220 (7.0) | – | 356 (2.4) |
| Duration of bisphosphonate use (mean ± SD, years) | 1.2 ± 1.7 | 2.5 ± 3.0 | ||
a
Including participants remaining at risk of lung cancer at year 6.
b
χ2 tests for categorical variables and Student’s t-tests for continuous variables were used to compare oral bisphosphonate users with nonusers. P value < 0.01.
c
Others include etidronate disodium, tiludronate disodium, pamidronate disodium and zoledronic acid.
WHI, Women’s Health Initiative; CT, clinical trials; OS, observational study; E, estrogen; E + P, estrogen plus progestin; SD, standard deviation.