Separate adjusted logistic regression analyses with different headache types as the dependent variables among Norwegian nurses
| Independent variables | Frequent headache* | Migraine | Tension-type headache | Chronic headache‡ | Medication-overuse headache |
| OR (95% CI)† n=1439–1519 | OR (95% CI)† n=1398–1476 | OR (95% CI)† n=1416–1495 | OR (95% CI)† n=1432–1512 | OR (95%CI)† n=1434–1514 | |
| Work schedule | |||||
| Day only | 1 | 1 | 1 | 1 | 1 |
| Two-shift | 1.07 (0.80 to 1.44) | 0.89 (0.62 to 1.28) | 1.11 (0.79 to 1.57) | 1.91 (0.68 to 5.32) | 1.49 (0.39 to 5.80) |
| Night only | 1.07 (0.65 to 1.77) | 0.75 (0.39 to 1.44) | 1.30 (0.74 to 2.28) | 1.18 (0.20 to 6.88) | 2.39 (0.32 to 17.65) |
| Three-shift | 1.01 (0.76 to 1.35) | 0.79 (0.55 to 1.14) | 1.31 (0.94 to 1.83) | 1.22 (0.42 to 3.56) | 0.86 (0.20 to 3.70) |
| Number of night shifts | |||||
| 0 night shifts | 1 | 1 | 1 | 1 | 1 |
| 1–20 night shifts | 0.86 (0.66 to 1.11) | 0.78 (0.56 to 1.09) | 1.27 (0.95 to 1.70) | 0.73 (0.30 to 1.74) | 0.51 (0.14 to 1.95) |
| >20 night shifts | 1.15 (0.90 to 1.47) | 0.80 (0.58 to 1.09) | 1.41 (1.07 to 1.86) | 0.82 (0.38 to 1.80) | 0.78 (0.27 to 2.29) |
| Number of quick returns | |||||
| 0 quick returns | 1 | 1 | 1 | 1 | 1 |
| 1–20 quick returns | 1.09 (0.81 to 1.46) | 0.83 (0.57 to 1.21) | 1.30 (0.92 to 1.82) | 1.12 (0.41 to 3.05) | 0.66 (0.15 to 3.01) |
| >20 quick returns | 1.06 (0.82 to 1.39) | 0.81 (0.58 to 1.12) | 1.23 (0.91 to 1.67) | 1.21 (0.50 to 2.95) | 1.18 (0.37 to 3.83) |
| Shift work disorder | |||||
| No | 1 | 1 | 1 | 1 | 1 |
| Yes | 2.04 (1.62 to 2.59) | 1.60 (1.21 to 2.12) | 1.19 (0.92 to 1.54) | 2.45 (1.25 to 4.80) | 1.67 (0.64 to 4.40) |
| Insomnia disorder | |||||
| No | 1 | 1 | 1 | 1 | 1 |
| Yes | 1.79 (1.43 to 2.23) | 1.55 (1.18 to 2.02) | 1.01 (0.79 to 1.29) | 3.03 (1.54 to 5.95) | 7.62 (2.48 to 23.41) |
Significant findings are shown in bold.
*Headache ≥1 days per month.
†Separate logistic regression analyses for each independent variable with adjustment for sex, age, percentage of full-time equivalent, marital status, and children living at home.
‡Headache >14 days per month.