Table 1.
Cohort Characteristics
| Total | Vitamin D < 20 | Vitamin D ≥ 20 | P Value | |
|---|---|---|---|---|
| Patients | 1,609 | 338 | 1,271 | … |
| Age, y | 65.3 (7.9) | 62.0 (7.9) | 66.1 (7.7) | < .001 |
| Sex, female | 673 (42) | 154 (46) | 519 (41) | .12 |
| Black race | 226 (14) | 97 (29) | 139 (10) | < .001 |
| BMI, kg/m2 | 27.3 (5.3) | 27.4 (5.7) | 27.3 (5.1) | .71 |
| Current smoker | 529 (33) | 161 (48) | 368 (30) | < .001 |
| Pack-years smoking, median (Q1-Q3) | 46 (35-62) | 45 (35-60) | 48 (36-63) | .20 |
| History of asthma | 363 (24) | 88 (28) | 275 (23) | .055 |
| Yearly income < $50,000 | 819 (51.0) | 211 (62.6) | 608 (47.8) | < .001 |
| FEV1/FVC ratio, baseline | 0.51 (0.13) | 0.50 (0.13) | 0.51 (0.13) | .13 |
| FEV1 % predicted, post-BD, baseline | 61.1 (23.1) | 57.5 (22.7) | 62.0 (23.1) | .001 |
| FVC % predicted, post-BD, baseline | 88.8 (19.9) | 86.1 (19.4) | 89.5 (20) | .005 |
| GOLD FEV1 severity | ||||
| Stage I | 346 (22) | 59 (17) | 287 (23) | .115 |
| Stage II | 712 (44) | 145 (43) | 567 (45) | |
| Stage III | 383 (24) | 92 (27) | 291 (23) | |
| Stage IV | 159 (10) | 40 (12) | 119 (9) | |
| Vitamin D supplementation | 383 (24) | 20 (6) | 363 (29) | < .001 |
| Vitamin D category | ||||
| < 10 ng/mL | 24 (1.05) | 24 (7) | 0 (0) | N/A |
| 10 to < 20 ng/mL | 314 (19.5) | 314 (93) | 0 (0) | |
| 20 to < 30 ng/mL | 535 (33.2) | 0 (0) | 535 (42) | |
| ≥ 30 ng/mL | 736 (45.7) | 0 (0) | 736 (58) | |
| Season of baseline visit | ||||
| Spring | 441 (27) | 94 (28) | 347 (27) | .003 |
| Summer | 423 (26) | 72 (21) | 351 (28) | |
| Fall | 414 (26) | 80 (24) | 334 (26) | |
| Winter | 330 (21) | 92 (27) | 238 (18) | |
| FEV1 % predicted, post-BD, 1 y | 61.1 (23.1) | 56.7 (22.4) | 63.4 (22.6) | < .001 |
| AECOPD in previous year, any | ||||
| 0 | 1,092 (69) | 207 (61) | 885 (70) | .005 |
| 1 | 273 (17) | 75 (23) | 198 (16) | |
| 2+ | 224 (14) | 53 (16) | 171 (14) | |
| AECOPD in previous year, severe | ||||
| 0 | 1,336 (84) | 258 (78) | 1,078 (86) | < .001 |
| 1 | 173 (11) | 50 (15) | 123 (10) | |
| 2+ | 76 (5) | 24 (7) | 52 (4) | |
| AECOPD in first year, any | ||||
| 0 | 1,125 (74) | 226 (72) | 899 (74) | .35 |
| 1 | 226 (15) | 48 (15) | 178 (15) | |
| 2+ | 172 (11) | 40 (13) | 132 (11) | |
| AECOPD in first year, severe | ||||
| 0 | 1,324 (87) | 273 (86) | 1,051 (88) | .59 |
| 1 | 123 (8) | 24 (8) | 99 (8) | |
| 2+ | 71 (5) | 22 (6) | 50 (4) |
All values represent No. (%) or mean (SD) unless otherwise indicated. P value, comparing vitamin D strata. AECOPD = acute exacerbation of COPD; BD = bronchodilator; GOLD = Global Initiative for Chronic Obstructive Lung Disease; Q1, Q3 = quartile 1, quartile 3.