Table 2.
Associations of different exposure metrics of night shift work with BMI, BF%, and FMI from generalized linear models.
| Exposure Metrics | BMI | FMI | PBF (%) | |||
|---|---|---|---|---|---|---|
| β | p | β | p | β | p | |
| Duration of night shifts (years) | ||||||
| Day work | 0 (Ref) | 0 (Ref) | 0 (Ref) | 0 (Ref) | 0 (Ref) | 0 (Ref) |
| Q1 (1–13) | −0.337 | 0.492 | −0.051 | 0.904 | 0.103 | 0.932 |
| Q2 (14–20) | −0.045 | 0.929 | 0.596 | 0.166 | 2.078 | 0.092 |
| Q3 (21–26) | −0.427 | 0.378 | 0.496 | 0.235 | 1.494 | 0.211 |
| Q4 (27–38) | −0.130 | 0.799 | 1.028 | 0.020 * | 3.761 | 0.003 * |
| p trend | 0.743 | 0.009 * | 0.002 * | |||
| Cumulative number of night shifts (nights) | ||||||
| Day work | 0 (Ref) | 0 (Ref) | 0 (Ref) | 0 (Ref) | 0 (Ref) | 0 (Ref) |
| Q1 (43–1157) | −0.380 | 0.437 | -0.071 | 0.866 | 0.062 | 0.959 |
| Q2 (1158–1790) | −0.033 | 0.947 | 0.590 | 0.167 | 2.118 | 0.083 |
| Q3 (1791–2411) | −0.387 | 0.428 | 0.622 | 0.140 | 1.820 | 0.131 |
| Q4 (2412–3580) | −0.152 | 0.768 | 0.928 | 0.038 * | 3.440 | 0.007 * |
| p trend | 0.783 | 0.011 * | 0.003 * | |||
| Cumulative length of night shifts (hours) | ||||||
| Day work | 0 (Ref) | 0 (Ref) | 0 (Ref) | 0 (Ref) | 0 (Ref) | 0 (Ref) |
| Q1 (344–9681) | −0.280 | 0.544 | 0.053 | 0.899 | 0.377 | 0.755 |
| Q2 (9682–14600) | 0.042 | 0.932 | 0.361 | 0.393 | 1.425 | 0.239 |
| Q3 (14601–19941) | −0.540 | 0.274 | 0.708 | 0.097 | 2.479 | 0.043 * |
| Q4 (19942–42960) | −0.204 | 0.691 | 0.961 | 0.031 * | 3.108 | 0.015 * |
| p trend | 0.599 | 0.011 * | 0.004 * | |||
| Average frequency of night shifts (nights/month) | ||||||
| Day work | 0 (Ref) | 0 (Ref) | 0 (Ref) | 0 (Ref) | 0 (Ref) | 0 (Ref) |
| <3 | −0.161 | 0.725 | 0.296 | 0.438 | 0.987 | 0.386 |
| 3–7 | −0.113 | 0.841 | 0.778 | 0.093 | 2.043 | 0.146 |
| >7 | −0.343 | 0.426 | 0.862 | 0.013 * | 2.252 | 0.036 * |
| p trend | 0.429 | 0.007 * | 0.030 * | |||
| Percentage of hours on night shifts | ||||||
| Day work | 0 (Ref) | 0 (Ref) | 0 (Ref) | 0 (Ref) | 0 (Ref) | 0 (Ref) |
| <20% | −0.149 | 0.779 | 0.240 | 0.588 | 0.778 | 0.556 |
| 20–30% | −0.554 | 0.314 | 0.136 | 0.765 | 0.504 | 0.712 |
| >30% | −0.175 | 0.675 | 0.916 | 0.006 * | 2.464 | 0.018 * |
| p trend | 0.670 | 0.038 * | 0.013 * | |||
* p < 0.05. Adjusted for age, smoking status, drinking status, education level, ethnicity, bedroom ambient light level, sleep duration, insomnia, sedentary behavior, DASH score, physical activity, marital status, menopausal status, and current use of oral contraceptives. The cut-off points of the average frequency of night shifts and percentage of hours on night shifts were chosen to secure a reasonable number of observations in each category.