Table 1.
Descriptive characteristics of the study sample
| Variables | All (N=2760) | NGT (n=2318) | IGT (n=442) |
| Age, years, mean (SD) | 46.5 (16.3) | 44.9 (15.8) | 55.4 (16.4) |
| Female, n (%) | 1394 (52.5) | 1171 (52.5) | 223 (52.5) |
| Ethnicity, n (%) | |||
| NH white | 1228 (68.6) | 1025 (68.2) | 203 (70.6) |
| NH black | 539 (11.2) | 453 (11.3) | 86 (10.7) |
| Mexican American | 330 (8.0) | 277 (8.1) | 53 (7.5) |
| Other Hispanic | 270 (5.9) | 228 (6.0) | 42 (5.0) |
| NH Asian | 322 (4.5) | 270 (4.4) | 52 (5.0) |
| Other | 71 (1.9) | 65 (2.1) | 6 (1.2) |
| Current smoker, n (%) | 563 (19.6) | 495 (20.3) | 68 (15.3) |
| Hypertension, n (%) | 890 (31.0) | 661 (27.7) | 229 (49.7) |
| Physical activity, n (%) | |||
| Poor | 1278 (43.8) | 1026 (42.0) | 252 (54.3) |
| Intermediate | 469 (17.3) | 392 (16.9) | 77 (19.9) |
| Ideal | 1013 (38.9) | 900 (41.2) | 113 (25.9) |
| BMI (kg/m2), mean (SD) | 28.5 (6.7) | 28.2 (6.6) | 30.4 (7.1) |
| Normal weight, n (%) | 943 (33.0) | 828 (34.7) | 115 (23.4) |
| Overweight, n (%) | 903 (33.6) | 777 (34.2) | 126 (29.8) |
| Obese, n (%) | 903 (33.4) | 704 (31.1) | 199 (46.8) |
| Ratio of family income to poverty, mean (SD) | 3.0 (1.7) | 2.9 (1.7) | 3 (1.6) |
| 2-hour glucose (mg/dL), mean (SD) | 106.6 (31.0) | 97.2 (22.0) | 160.9 (15.7) |
| Fasting glucose (mg/dL), mean (SD) | 97.4 (9.4) | 96.4 (8.9) | 103.1 (10.2) |
| Fasting insulin* (µU/mL), mean (SD) | 12.0 (9.3) | 11.4 (8.8) | 15.6 (10.9) |
| HOMA-IR*, mean (SD) | 3.0 (2.5) | 2.8 (2.3) | 4.1 (3.0) |
| Rest-activity parameters, mean (SD) | |||
| RA | 0.85 (0.12) | 0.86 (0.11) | 0.82 (0.13) |
| IS | 0.59 (0.14) | 0.59 (0.14) | 0.59 (0.14) |
| IV | 0.70 (0.22) | 0.68 (0.21) | 0.76 (0.23) |
| M10 start time | 9:18 (150 min) | 9:24 (150 min) | 8:48 (138 min) |
| L5 start time | 0:47 (99 min) | 0:49 (96 min) | 0:33 (102 min) |
% and mean (SD) were weight-adjusted.
*n=418 for IGT and n=2249 for NGT.
BMI, body mass index; HOMA-IR, homeostasis model assessment for insulin resistance; IGT, impaired glucose tolerance; IS, interdaily stability; IV, intradaily variability; L5, least active continuous 5-hour period; M10, most active continuous 10-hour period; NGT, normal glucose tolerance; NH, non-Hispanic; RA, relative amplitude.