Baseline characteristics of homeostatic model assessment study participants
| Characteristic | Placebo (N = 195) | Selenium (N = 205) | Total (N = 400) | P value* |
| Age | ||||
| Mean (SD) | 62.6 (8.5) | 63.4 (9.3) | 63.0 (8.9) | 0.32 |
| Median (Q1, Q3) | 64.0 (57.0, 69.0) | 63.0 (57.0, 71.0) | 63.0 (57.0, 70.0) | |
| Body mass index | ||||
| Mean (SD) | 29.2 (4.9) | 29.2 (5.4) | 29.2 (5.2) | 0.99 |
| Median (Q1, Q3) | 29.2 (25.5, 32.4) | 27.8 (25.6, 32.0) | 28.5 (25.5, 32.3) | |
| Selenium dietary intake (µg/day)† | ||||
| Mean (SD) | 107.8 (63.0) | 101.7 (56.1) | 104.6 (59.5) | 0.32 |
| Median (Q1, Q3) | 93.7 (70.5, 128.9) | 88.8 (65.1, 124.4) | 91.1 (67.9, 126.0) | |
| Selenium supplemental intake (µg/day) | ||||
| Mean (SD) | 7.7 (11.7) | 5.5 (7.2) | 6.5 (9.7) | 0.03 |
| Median (Q1, Q3) | 10.0 (0.0, 10.0) | 0.0 (0.0, 10.0) | 0.0 (0.0, 10.0) | |
| Plasma selenium (ng/mL)‡ | ||||
| Mean (SD) | 137.2 (24.2) | 140.9 (27.8) | 139.1 (26.1) | 0.16 |
| Median (Q1, Q3) | 134.4 (121.7, 152.1) | 136.0 (124.0, 155.5) | 134.6 (122.6, 153.8) | |
| Gender | ||||
| Female | 62 (31.8%) | 74 (36.1%) | 136 (34.0%) | 0.36 |
| Male | 133 (68.2%) | 131 (63.9%) | 264 (66.0%) | |
| Ethnicity | ||||
| Non-Hispanic | 186 (95.4%) | 192 (93.7%) | 378 (94.5%) | 0.45 |
| Hispanic | 9 (4.6%) | 13 (6.3%) | 22 (5.5%) | |
| Race | ||||
| Native American | 0 (0.0%) | 2 (1.0%) | 2 (0.5%) | 0.21 |
| Asian | 1 (0.5%) | 1 (0.5%) | 2 (0.5%) | |
| African–American | 8 (4.1%) | 7 (3.4%) | 15 (3.8%) | |
| Other | 0 (0.0%) | 4 (2.0%) | 4 (1.0%) | |
| White | 186 (95.4%) | 191 (93.2%) | 377 (94.3%) | |
| Education | ||||
| High school | 43 (22.1%) | 39 (19.1%) | 82 (20.6%) | 0.04 |
| Some college | 55 (28.2%) | 78 (38.2%) | 133 (33.3%) | |
| College degree | 35 (17.9%) | 36 (17.6%) | 71 (17.8%) | |
| Postgraduate | 57 (29.2%) | 48 (23.5%) | 105 (26.3%) | |
| Cigarette smoking status | ||||
| Current smoker | 17 (8.9%) | 22 (10.8%) | 39 (9.9%) | 0.5 |
| Previous smoker | 91 (47.6%) | 104 (51.2%) | 195 (49.5%) | |
| Never smoker | 83 (43.5%) | 77 (37.9%) | 160 (40.6%) | |
| Diabetes | ||||
| No diabetes | 176 (90.3%) | 193 (94.1%) | 369 (92.3%) | 0.15 |
| Has diabetes | 19 (9.7%) | 12 (5.9%) | 31 (7.8%) | |
| Personal history of cancer | ||||
| Never had cancer | 185 (94.9%) | 196 (95.6%) | 381 (95.3%) | 0.73 |
| Had cancer | 10 (5.1%) | 9 (4.4%) | 19 (4.8%) | |
| Aspirin use in last 20 years | ||||
| 0–1 year | 115 (59.0%) | 115 (56.1%) | 230 (57.5%) | 0.19 |
| 1 to <5 years | 40 (20.5%) | 49 (23.9%) | 89 (22.3%) | |
| 5 to <10 years | 16 (8.2%) | 8 (3.9%) | 24 (6.0%) | |
| 10+ years | 24 (12.3%) | 33 (16.1%) | 57 (14.3%) | |
| Non-steroidal anti-inflammatory drug use in last 20 years | ||||
| 0 to <1 year | 176 (90.3%) | 176 (85.9%) | 352 (88.0%) | 0.03 |
| 1 to <5 years | 9 (4.6%) | 23 (11.2%) | 32 (8.0%) | |
| 5 to <10 years | 3 (1.5%) | 4 (2.0%) | 7 (1.8%) | |
| 10+ years | 7 (3.6%) | 2 (1.0%) | 9 (2.3%) | |
| Clinic | ||||
| Phoenix | 142 (72.8%) | 148 (72.2%) | 290 (72.5%) | 0.33 |
| Colorado | 43 (22.1%) | 48 (23.4%) | 91 (22.8%) | |
| Western New York | 3 (1.5%) | 0 (0.0%) | 3 (0.8%) | |
| Tucson | 7 (3.6%) | 9 (4.4%) | 16 (4.0%) | |
*t-test or analysis of variance for continuous variables, χ2 categorical variables.
†From Arizona Food Frequency Questionnaire.
‡From baseline plasma.