Table 1. Clinical and demographic characteristics according to HBA copy number.
| HBA copy number | ||||||
|---|---|---|---|---|---|---|
| All Subjects | 2 | 3 | 4 | ≥ 5* | P value † | |
| Subjects, N (%) | 9,684 (100) | 387 (4) | 2685 (28) | 6507 (67) | 105 (1) | NA |
| Age, years | 63 (57, 70) | 64 (58, 70) | 64 (57, 71) | 63 (57, 70) | 67 (61, 73) | 0.004 |
| Female sex, N (%) | 5952 (61) | 243 (63) | 1638 (61) | 4013 (62) | 58 (55) | 0.50 |
| Body mass index, kg/m 2 | 29.7 (26.1, 34.4) | 30.3 (26.9, 34.9) | 29.8 (26.1, 34.4) | 29.7 (26.1, 34.4) | 30.6 (27.5, 34.9) | 0.19 |
| Smoking status, N (%) | 0.58 | |||||
| Never | 4368 (45) | 167 (43) | 1225 (46) | 2931 (45) | 45 (43) | |
| Past | 3588 (37) | 156 (41) | 986 (37) | 2401 (37) | 45 (43) | |
| Current | 1683 (17) | 61 (16) | 460 (17) | 1148 (18) | 14 (13) | |
| Region, N (%) | 0.06 | |||||
| Non-Belt | 4816 (50) | 169 (44) | 1367 (51) | 3220 (49) | 60 (57) | |
| Belt | 3197 (33) | 138 (36) | 850 (32) | 2181 (34) | 28 (27) | |
| Buckle | 1671 (17) | 80 (21) | 468 (17) | 1106 (17) | 17 (16) | |
| Medically insured, N (%) | 8716 (90) | 350 (91) | 2428 (91) | 5842 (90) | 99 (91) | 0.61 |
| Education level, N (%) | 0.18 | |||||
| Less than high school | 1896 (20) | 70 (18) | 532 (20) | 1271 (20) | 23 (21) | |
| High school graduate | 2677 (28) | 111 (29) | 774 (29) | 1762 (27) | 30 (28) | |
| Some college | 2572 (27) | 99 (27) | 738 (28) | 1707 (26) | 28 (28) | |
| College graduate or more | 2527 (26) | 106 (27) | 639 (24) | 758 (27) | 24 (23) | |
| Income, N (%) | 0.15 | |||||
| ≤ $20K | 2600 (31) | 105 (30) | 721 (31) | 1742 (30) | 32 (33) | |
| $20K–$34K | 2513 (30) | 107 (31) | 711 (30) | 1681 (30) | 32 (33) | |
| $35K–$74K | 2489 (29) | 103 (30) | 708 (30) | 1651 (29) | 27 (28) | |
| ≥ $75K | 894 (10) | 32 (9) | 210 (9) | 670 (11) | 6 (6) | |
| Chronic Kidney disease, N (%) | 2498 (27) | 83 (22) | 688 (27) | 1692 (27) | 35 (35) | 0.05 |
| Diabetes mellitus, N (%) | 2818 (29) | 103 (27) | 808 (30) | 1878 (29) | 29 (28) | 0.47 |
| Total Cholesterol, mg/dL | 190 (165, 217) | 188 (162, 215) | 189 (164, 217) | 191 (165, 218) | 193 (172, 217) | 0.15 |
| C-reactive protein, mg/L units | 2.9 (1.2, 6.5) | 3.3 (1.3, 7.5) | 2.8 (1.1, 6.3) | 2.9 (1.2, 6.5) | 2.9 (1.1, 6.0) | 0.12 |
| Hemoglobin, g/dL | 13.1 (12.2, 14.0) | 12.4 (11.6, 13.2) | 12.9 (12.0, 13.8) | 13.2 (12.4, 14.1) | 13.0 (12.1, 14.1) | < 0.0001 |
| MCV, fL | 88 (84, 92) | 74 (72, 77) | 85 (82, 87) | 90 (87, 93) | 89 (87, 92) | < 0.0001 |
| MCH, pg | 29.6 (27.9, 30.9) | 23.8 (22.9, 24.8) | 27.9 (26.9, 29.0) | 30.3 (29.1, 31.4) | 29.9 (29.1, 31.1) | < 0.0001 |
| MCHC, g/dL | 33.4 (32.9, 33.9) | 32.1 (31.6, 32.6) | 33.0 (32.6, 33.5) | 33.6 (33.2, 34.1) | 33.8 (33.2, 34.0) | < 0.0001 |
| RDW-CV, % | 14.0 (13.3, 14.8) | 15.0 (14.4, 15.9) | 14.2 (13.5, 15.1) | 13.8 (13.2, 14.6) | 13.6 (13.2, 14.2) | < 0.0001 |
| Prevalent hypertension ‡ , N (%) | 7439 (77) | 304 (79) | 2070 (77) | 4978 (77) | 87 (83) | 0.20 |
| Resistant hypertension, N (%) | 1044 (11) | 50 (13) | 299 (11) | 679 (10) | 16 (15) | 0.16 |
| Anti-hypertensive medication, N (%) | 0.20 | |||||
| None | 3175 (33) | 134 (35) | 877 (33) | 2135 (32) | 29 (28) | |
| One | 1966 (20) | 67 (17) | 525 (20) | 1344 (21) | 30 (29) | |
| Two or more | 4543 (47) | 186 (48) | 1283 (48) | 3028 (45) | 46 (44) | |
| Systolic blood pressure, mm Hg | 130 (120, 140) | 130 (120, 140) | 130 (120, 141) | 130 (120, 140) | 133 (120, 144) | 0.42 |
| Diastolic blood pressure, mm Hg | 79 (72, 84) | 79 (71, 84) | 79 (72, 84) | 79 (71, 84) | 80 (71, 86) | 0.82 |
| Pulse pressure, mm Hg | 51 (43, 60) | 51 (43, 60) | 51 (43, 60) | 51 (43, 60) | 53 (45, 64) | 0.30 |
HBA = alpha globin gene; P = p value; N = number; K = thousand; RBC = red blood cell; MCV = mean corpuscular volume; MCH = mean corpuscular hemoglobin; MCHC = mean corpuscular hemoglobin concentration; RDW-CV = red cell distribution width-coefficient of variation; No. = number. Values are median (25th, 75th percentile) except where otherwise indicated.
*105 subjects had 5 HBA gene copies and 3 subjects had 6 HBA copies;
†P values for tests of differences by alpha globin copy number using chi-square test for categorical variables and Kruskal-Wallis test for continuous variables;
‡261 participants met the definition of prevalent hypertension solely based on having two or more anti-hypertensive medications on pill bottle review.