PRs (95% CI) for sleep duration, quality, ADL score and insomnia in relation to regular shiftwork status among US workers (NHANES, 2005–2008)*
| Outcome/model | Regular shiftwork status | ||||
|---|---|---|---|---|---|
| Daytime shift | Night shift | Rotating shift | Evening shift | Another schedule† | |
| Sleep duration | |||||
| <7 vs ≥7 hours per work or week night | |||||
| Unadjusted | Ref. | 1.72 (1.52 to 1.94) | 1.15 (0.99 to 1.33) | 1.09 (0.93 to 1.27) | 1.03 (0.91 to 1.17) |
| Model 1‡ | Ref. | 1.70 (1.50 to 1.93) | 1.15 (0.99 to 1.34) | 1.10 (0.95 to 1.27) | 1.03 (0.90 to 1.17) |
| Model 2§ | Ref. | 1.70 (1.48 to 1.96) | 1.14 (0.96 to 1.35) | 1.06 (0.91 to 1.24) | 1.06 (0.94 to 1.21) |
| Sleep quality index¶ | |||||
| Poor quality | |||||
| Unadjusted | Ref. | 1.67 (1.37 to 2.03) | 1.05 (0.80 to 1.36) | 1.25 (0.95 to 1.66) | 1.01 (0.81 to 1.27) |
| Model 1‡ | Ref. | 1.70 (1.40 to 2.05) | 1.05 (0.80 to 1.37) | 1.25 (0.94 to 1.65) | 1.03 (0.83 to 1.28) |
| Model 2** | Ref. | 1.52 (1.24 to 1.85) | 1.07 (0.82 to 1.39) | 1.12 (0.82 to 1.52) | 1.06 (0.85 to 1.32) |
| Moderate quality | |||||
| Unadjusted | Ref. | 0.85 (0.65 to 1.10) | 1.14 (0.92 to 1.42) | 1.10 (0.90 to 1.33) | 1.29 (1.10 to 1.52) |
| Model 1‡ | Ref. | 0.84 (0.65 to 1.08) | 1.09 (0.88 to 1.34) | 1.04 (0.86 to 1.27) | 1.29 (1.10 to 1.50) |
| Model 2** | Ref. | 0.86 (0.63 to 1.19) | 1.07 (0.86 to 1.33) | 1.08 (0.88 to 1.32) | 1.25 (1.06 to 1.47) |
| Sleep-related ADL score†† | |||||
| ≥2 vs <2 | |||||
| Unadjusted | Ref. | 1.53 (1.24 to 1.89) | 0.99 (0.81 to 1.21) | 1.23 (1.01 to 1.50) | 1.17 (0.96 to 1.41) |
| Model 1‡ | Ref. | 1.49 (1.20 to 1.85) | 0.94 (0.77 to 1.14) | 1.15 (0.96 to 1.40) | 1.19 (0.98 to 1.45) |
| Model 2‡‡ | Ref. | 1.39 (1.11 to 1.73) | 0.98 (0.82 to 1.18) | 1.11 (0.91 to 1.36) | 1.19 (0.99 to 1.43) |
| Insomnia | |||||
| Unadjusted | Ref. | 2.19 (1.58 to 3.03) | 1.11 (0.73 to 1.68) | 1.15 (0.82 to 1.61) | 0.83 (0.57 to 1.22) |
| Model 1‡ | Ref. | 2.19 (1.59 to 3.02) | 1.08 (0.71 to 1.65) | 1.11 (0.81 to 1.53) | 0.86 (0.58 to 1.25) |
| Model 2§§ | Ref. | 2.03 (1.30 to 3.17) | 1.11 (0.65 to 1.88) | 0.92 (0.59 to 1.42) | 0.88 (0.58 to 1.34) |
*Weighted estimates derived from logistic regression for sleep duration as a binary outcome (<7 hours referenced to ≥7 hours per week/work day), sleep-related ADL score (≥2 referenced to <2) and insomnia (yes referenced to no); and from multinomial logistic regression for sleep quality index (poor and moderate referenced to good sleep quality).
†No additional information is available on this shift category. This category was selected by the participant if none of the other categories applied. It could include a split shift consisting of two distinct work periods each day, an irregular schedule arranged by the employer or any other schedule not already specified.
‡Model 1, adjusted for the demographic characteristics of age group, gender, race/ethnicity and education.
§Model 2: model 1 further adjusted for general health status, symptomatic depression, body mass index, current smoking status and weekly working hours.
¶Categorised as poor sleep quality if the response to any of the six sleep problem items was 16–30 times/month; else as moderate sleep quality if any response was 5–15 times/month and all others as good sleep quality.
**Model 2: model 1 further adjusted for self-rated health status, symptomatic depression, current smoking status and weekly working hours.
††A score ≥2 is considered to indicate a greater daily sleep-related impairment than a score <2.
‡‡Model 2: model 1 further adjusted for self-rated health status, symptomatic depression and prescription medication use.
§§Model 2: model 1 further adjusted for self-rated health status, symptomatic depression, prescription medication use, weekly working hours and alcohol intake.
ADL, activities of daily living; NHANES, National Health and Nutrition Examination Survey; PR, prevalence ratio.