N (%) | Median duration in months (25th, 75th percentile) | Model 1 time ratio (95% CI) | Model 2 time ratio (95% CI) | Model 3 time ratio (95% CI) | |
---|---|---|---|---|---|
Typical work schedule over past year | |||||
Days only | 1006 (58.0) | 3.5 (1, 12) | 1.0 (REF) | 1.0 (REF) | 1.0 (REF) |
Evenings only | 87 (5.0) | 3.0 (1, 8) | 1.05 (0.82 to 1.33) | 1.07 (0.84 to 1.35) | 1.06 (0.84 to 1.35) |
Nights only | 298 (17.2) | 3.0 (1, 8) | 1.01 (0.87 to 1.16) | 1.01 (0.87 to 1.16) | 0.94 (0.81 to 1.08) |
Rotating with nights | 273 (15.7) | 3.0 (1, 8) | 0.90 (0.78 to 1.04) | 0.93 (0.80 to 1.07) | 0.88 (0.76 to 1.02) |
Rotating no nights | 71 (4.1) | 3.0 (1, 9) | 0.86 (0.67 to 1.12) | 0.89 (0.69 to 1.15) | 0.87 (0.67 to 1.12) |
Weekly hours of nursing work over past year (h/week) | |||||
1–20 | 128 (7.4) | 3.0 (1, 9.5) | 0.94 (0.77 to 1.15) | 0.93 (0.77 to 1.13) | 0.98 (0.80 to 1.19) |
21–40 | 1144 (65.8) | 3.0 (1, 8) | 1.0 (REF) | 1.0 (REF) | 1.0 (REF) |
>40 | 467 (26.9) | 5.0 (2, 12) | 1.24 (1.10 to 1.40) | 1.21 (1.08 to 1.36) | 1.20 (1.07 to 1.35) |
P-trend | 0.0004 | 0.001 | 0.005 | ||
Frequency of night work in past month (night shifts/week) | |||||
None | 1170 (67.6) | 3.0 (1, 11) | 1.0 (REF) | 1.0 (REF) | 1.0 (REF) |
≤1 | 207 (12.0) | 3.0 (1, 11) | 1.06 (0.90 to 1.24) | 1.08 (0.92 to 1.26) | 1.02 (0.87 to 1.20) |
2–3 | 266 (15.4) | 3.0 (1, 7) | 0.95 (0.82 to 1.10) | 0.97 (0.84 to 1.12) | 0.92 (0.79 to 1.07) |
>3 | 89 (5.1) | 4.0 (1, 10) | 1.10 (0.87 to 1.39) | 1.11 (0.88 to 1.40) | 1.01 (0.80 to 1.27) |
P-trend | 0.93 | 0.78 | 0.47 | ||
Duration of rotating night shifts (year) | |||||
Never | 910 (52.5) | 3.0 (1, 10) | 1.0 (REF) | 1.0 (REF) | 1.0 (REF) |
<1 | 417 (24.0) | 3.0 (1, 10) | 1.02 (0.90 to 1.16) | 1.02 (0.91 to 1.16) | 1.03 (0.91 to 1.17) |
1–2 | 246 (14.2) | 3.0 (1, 12) | 1.06 (0.91 to 1.23) | 1.05 (0.90 to 1.22) | 1.03 (0.88 to 1.20) |
≥3 | 161 (9.3) | 4.0 (2, 12) | 1.06 (0.88 to 1.28) | 1.09 (0.91 to 1.30) | 1.04 (0.86 to 1.25) |
P-trend | 0.43 | 0.34 | 0.66 | ||
Duration of permanent night shifts (years) | |||||
Never | 757 (43.6) | 3.0 (1, 10) | 1.0 (REF) | 1.0 (REF) | 1.0 (REF) |
<1 | 491 (28.3) | 3.0 (1, 10) | 1.05 (0.93 to 1.19) | 1.03 (0.91 to 1.16) | 1.03 (0.91 to 1.17) |
1–2 | 285 (16.4) | 4.0 (1, 11) | 1.11 (0.95 to 1.28) | 1.09 (0.94 to 1.26) | 1.09 (0.94 to 1.26) |
≥3 | 205 (11.8) | 4.0 (1, 12) | 1.00 (0.84 to 1.18) | 0.97 (0.82 to 1.15) | 0.95 (0.80 to 1.12) |
P-trend | 0.86 | 0.88 | 0.66 | ||
Duration of night shifts (years) | |||||
Never | 436 (25.1) | 3.0 (1, 10.5) | 1.0 (REF) | 1.0 (REF) | 1.0 (REF) |
<1 | 401 (23.1) | 3.0 (1, 8) | 0.93 (0.80 to 1.08) | 0.94 (0.81 to 1.08) | 0.95 (0.82 to 1.10) |
1–1.9 | 388 (22.4) | 3.0 (1, 8) | 0.97 (0.84 to 1.13) | 0.96 (0.83 to 1.11) | 0.96 (0.83 to 1.12) |
2–4 | 270 (15.6) | 3.0 (1, 11) | 1.00 (0.85 to 1.18) | 0.99 (0.84 to 1.16) | 0.97 (0.82 to 1.15) |
>4 | 239 (13.8) | 5.0 (2, 12) | 1.11 (0.93 to 1.32) | 1.10 (0.92 to 1.30) | 1.05 (0.88 to 1.26) |
P-trend | 0.13 | 0.19 | 0.39 |
Accelerated failure time models were used to estimate the time ratios and 95% CIs. Tests for linear trend use the median values in each category as a continuous variable.
Model 1 is adjusted for age.
Model 2 is adjusted for age, race, BMI, smoking status and marital status.
Model 3 is adjusted for variables in Model 2 and current night work, weekly hours of nursing work, frequency of moving or lifting a heavy load, duration of night work, and current exposure to radiation, antineoplastic drugs, high-level disinfectants, and anaesthesia gas.
BMI, body mass index.