Table 1.
Baseline Characteristics by Tertile of Dietary Protein Intake: The Health, Aging, and Body Composition Study
| Dietary Protein Tertile, % of Total Energy Intake | p Value | ||||
|---|---|---|---|---|---|
| Overall | <13% | 13%–15% | ≥15% | ||
| N | 2160 | 718 | 703 | 739 | |
| Age (y) | 73.5 ± 2.8 | 73.5 ± 2.9 | 73.4 ± 2.8 | 73.7 ± 2.9 | .31 |
| Female gender, n (%) | 1113 (51.5) | 335 (47.0) | 371 (52.2) | 407 (55.3) | .006 |
| Black race, n (%) | 773 (35.8) | 305 (42.8) | 236 (33.2) | 232 (31.5) | <.001 |
| Study site, Pittsburgh, n (%) | 1130 (52.3) | 392 (55.0) | 363 (51.1) | 375 (51.0) | .22 |
| Smoking history, n (%) | <.001 | ||||
| Never | 970 (44.9) | 268 (37.6) | 333 (46.8) | 369 (50.1) | |
| Current | 192 (8.9) | 104 (14.6) | 44 (6.2) | 44 (6.0) | |
| Former | 998 (46.2) | 341 (47.8) | 334 (47.0) | 323 (43.9) | |
| Alcohol use, n (%) | .09 | ||||
| Never | 587 (27.2) | 171 (24.0) | 204 (28.7) | 212 (28.8) | |
| Current | 1118 (51.8) | 394 (55.3) | 347 (48.8) | 377 (51.2) | |
| Former | 455 (21.1) | 148 (20.8) | 160 (22.5) | 147 (20.0) | |
| Education completed, n (%) | .17 | ||||
| Less than high school | 466 (21.6) | 166 (23.3) | 154 (21.7) | 146 (19.8) | |
| High school | 719 (33.3) | 250 (35.1) | 222 (31.2) | 247 (33.6) | |
| Postsecondary education | 975 (45.1) | 297 (41.7) | 335 (47.1) | 343 (46.6) | |
| Minutes of walking/wk, n (%) | .009 | ||||
| 0 (sedentary) | 870 (40.3) | 313 (43.9) | 285 (40.1) | 272 (37.0) | |
| 1–149 | 672 (31.1) | 209 (29.3) | 240 (33.8) | 223 (30.3) | |
| ≥150 | 618 (28.6) | 191 (26.8) | 186 (26.2) | 241 (32.7) | |
| BMI (kg/m2) | 27.2 ± 4.6 | 27.1 ± 4.7 | 27.0 ± 4.4 | 27.5 ± 4.8 | .07 |
| Dietary intake | |||||
| Total energy (kcal/d) | 1838 ± 626 | 1933 ± 656 | 1825 ± 589 | 1758 ± 619 | <.001 |
| Fat (% energy) | 33 ± 7 | 34 ± 7 | 34 ± 7 | 32 ± 8 | <.001 |
| Carbohydrate (% energy) | 54 ± 8 | 55 ± 8 | 53 ± 8 | 52 ± 8 | <.001 |
| Protein (% energy) | 14 ± 3 | 12 ± 1 | 14 ± 1 | 18 ± 2 | <.001 |
| Protein (g/kg body weight/d) | 0.9 ± 0.4 | 0.8 ± 0.3 | 0.9 ± 0.3 | 1.1 ± 0.4 | <.001 |
| Osteoporosis diagnosis, n (%) | 226 (10.5) | 65 (9.1) | 78 (11.0) | 83 (11.3) | .35 |
| Osteoporosis medications, n (%) | 100 (4.6) | 24 (3.4) | 37 (5.2) | 39 (5.3) | .15 |
| Dietary calcium intake (mg) | 773 ± 360 | 685 ± 293 | 779 ± 343 | 854 ± 413 | <.001 |
| Dietary vitamin D intake (IU) | 208 ± 133 | 182 ± 116 | 209 ± 128 | 232 ± 147 | .001 |
| Calcium supplements, n (%) | 424 (19.6) | 107 (15.0) | 140 (19.7) | 177 (24.0) | <.001 |
| Vitamin D supplements, n (%) | 194 (9.0) | 47 (6.6) | 70 (9.8) | 77 (10.5) | .02 |
| Oral estrogen, n (%) | 258 (11.9) | 63 (8.8) | 91 (12.8) | 104 (14.1) | .006 |
| Fractured bone after age 45, n (%) | 493 (22.8) | 170 (23.8) | 158 (22.2) | 165 (22.4) | .73 |
| Preexisting vertebral fracture, n (%) | 72 (3.3) | 25 (3.5) | 25 (3.5) | 22 (3.0) | .81 |
| Cognitive function, Modified Mini-Mental State Examination (3MS) | 91.0 ± 7.5 | 90.4 ± 8.0 | 91.2 ± 8.0 | 91.5 ± 8.2 | .02 |
| Physical Performance Battery Score (range: 0–4) | 2.2 ± 0.5 | 2.2 ± 0.5 | 2.3 ± 0.5 | 2.3 ± 0.5 | .97 |
| Fall in the prior 12 mo, n (%) | 463 (21.4) | 144 (20.2) | 158 (22.2) | 161 (21.9) | .61 |
Notes: BMI = body mass index. Data presented as means ± SD for the overall population unless otherwise noted as n (%). Statistical comparisons across protein tertiles were assessed with analysis of variance for continuous variables or chi-squared tests for categorical variables.