Table 2. Sleep parameters of shift workers according to vitamin D levels.
| Characteristics | All workers ( n = 82) |
25(OH)D (ng/mL) | p * | |
|---|---|---|---|---|
| ≥ 20 ( n = 57) | < 20 ( n = 25) | |||
| Sleep features | ||||
| Total sleep time (hours) | 6.5 (5.8–6.9) | 6.6 (5.9–6.9) | 6.2 (5.4–6.8) | 0.095 |
| Sleep latency (min) | 13.2 (8.5–24.0) | 11.5 (8.5–19.5) | 23.0 (8.5–28.5) | 0.016 |
| REM sleep latency (min) | 99.7 (79.0–147.0) | 100.5 (79.0–136.0) | 99.0 (80.0–147.0) | 0.705 |
| Sleep efficiency (%) | 85.3 (76.9–89.2) | 86.5 (80.0–90.0) | 80.9 (73.8–86.6) | 0.017 |
| AHI (events/hour) | 13.7 (7.6–22.9) | 13.6 (7.9–22.3) | 16.3 (6.5–26.1) | 0.687 |
| MAI (events/hour) | 8.6 (5.5–12.4) | 7.7 (5.3–11.7) | 11.3 (7.6–13.2) | 0.103 |
| Arterial oxygen saturation | ||||
| SaO2 average (%) | 95.0 (94.0–96.0) | 95.0 (94.0–96.0) | 96.0 (95.0–96.0) | 0.221 |
| SaO2 minimum (%) | 87.0 (83.0–89.0) | 87.0 (84.0–89.0) | 86.0 (83.0–88.0) | 0.634 |
| Time with SaO2 < 90%, min | 1.4 (0.1–4.8) | 1.4 (0.0–7.0) | 1.4 (0.2–4.7) | 0.776 |
| Sleep stages | ||||
| N1 (% TST) | 5.7 (4.4–7.4) | 5.7 (4.3–7.2) | 5.3 (4.6–7.4) | 0.919 |
| N2 (%TST) | 59.1 (54.0–63.7) | 59.7 (53.6–64.3) | 56.8 (54.1–61.6) | 0.308 |
| N3 (%TST) | 15.8 (11.5–19.8) | 14.7 (11.2–19.0) | 18.1 (14.7–20.3) | 0.323 |
| REM (%TST) | 17.7 (14.5–24.6) | 18.5 (13.8–24.6) | 17.3 (15.8–23.0) | 0.875 |
Results are presented as median (interquartile range);
p * value for Mann Whitney test.
Abrevviations: MAI: microarousal index; AHI, apnea-hypopnea index; SaO2: arterial oxygen saturation; REM: rapid eye movement; TST: total sleep time.