Results from regression analyses of melatonin levels by chronotype within the night shift workers (NSW)
| Comparison | % difference in 6-sulfatoxymelatonin levels* | 95% CI |
|---|---|---|
| Day sleep vs night sleep | ||
| Dichotomous† | ||
| Evening | −21.5%‡ | (−36.7% to −6.3%) |
| Morning§ | −40.9%¶ | (−52.5% to −29.4%) |
| Trichotomous** | ||
| Evening | −17.7% | (−36.4% to +1.1%) |
| Intermediate | −27.9%¶ | (−42.1% to −13.6%) |
| Morning§ | −52.8%¶ | (−65.0% to −40.7%) |
| Night work vs night sleep | ||
| Dichotomous† | ||
| Evening | −52.3%¶ | (−58.1% to −46.5%) |
| Morning§ | −32.5%¶ | (−40.6% to −24.4%) |
| Trichotomous** | ||
| Evening | −57.3%¶ | (−63.6% to −51.0%) |
| Intermediate§ | −39.8%¶ | (−47.3% to −32.4%) |
| Morning§ | −27.4%¶ | (−39.5% to −15.3%) |
*Analysed using the natural log transformation and adjusted for the effects of age, gender, hours of darkness, body mass index, number of alcoholic beverages consumed and use of psychotherapeutics; reference category is night sleep; for example, in dichotomous analysis, evening type night shift workers during daytime sleep had 21.5% lower levels of 6-sulfatoxmelatonin than all night shift workers during night-time sleep.
†Evening: chronoscore 33 or less; morning: chronoscore 34 or higher.
‡p < 0.05, two-sided t test.
§Test for difference from evening-type category: p<0.01, using two-sided t test.
¶p<0.001, two-sided t test.
**Evening: chronoscore 28 or less; intermediate: chronoscore 29–39; morning: chronoscore 40 or higher.