Patient demographics and preoperative clinical characteristics
| VDD (≤20 ng/mL) (n=496) Mean (±SD) or n (%) | Non-VDD (>20 ng/mL) (n=488) Mean (±SD) or n (%) | P value | |
| Age | 48 (±15) | 51 (±15) | <0.01 |
| Sex | 0.83 | ||
| Female | 407 (82.1) | 403 (82.6) | |
| Male | 89 (17.9) | 85 (17.4) | |
| BMI (kg/m2) | 30.2 (±7.8) | 29.5 (±7.3) | 0.48 |
| Preoperative vitamin D (ng/mL) | 9.6 (±8.3) | 32.6 (±12.0) | <0.01 |
| Length of time from vitamin D measurement to surgery date (days) | 14.6 (±168.7) | 44.3 (±166.5) | <0.01 |
| Preoperative serum calcium (mg/dL) | 8.4 (±1.0) | 8.6 (±0.9) | <0.01 |
| Preoperative PTH (pg/mL) | 36.4 (±28.5) | 34.8 (±27.0) | 0.60 |
| Race/ethnicity | <0.01* | ||
| Caucasian | 315 (63.5) | 363 (74.4) | |
| African American | 115 (23.2) | 67 (13.7) | |
| Asian | 10 (2.0) | 15 (3.1) | |
| Native American | 7 (1.4) | 7 (1.4) | |
| Hispanic | 5 (1.0) | 4 (0.8) | |
| Other | 44 (8.9) | 32 (6.6) | |
| Urban | 388 (78.2) | 352 (72.1) | 0.03 |
| Rural | 108 (21.8) | 136 (27.9) | |
| Diuretic use | 24 (4.8) | 24 (4.9) | 0.95 |
| Proton pump inhibitor use | 66 (13.3) | 55 (11.3) | 0.33 |
| Surgical pathology | 253 (66.2) | 274 (68.0) | 0.60 |
| Malignant | |||
| Season of surgery | 0.43 | ||
| Winter | 114 (23.0) | 94 (19.3) | |
| Spring | 118 (23.8) | 133 (27.3) | |
| Summer | 127 (25.6) | 124 (25.4) | |
| Autumn | 137 (27.6) | 137 (28.1) | |
| Performance of neck dissection | 2 (0.4) | 13 (2.7) | <0.01* |
χ2 test and Fisher’s exact test for categorical variables and t-test for numerical variables.
*Fisher’s exact test.
BMI, body mass index; PTH, parathyroid hormone; VDD, vitamin D deficiency.