Results from regression analyses of melatonin levels by chronotype, night shift workers (NSW) relative to all day shift workers (DSW)
| Comparison | % difference in NSW 6-sulfatoxymelatonin levels, relative to DSW levels* | 95% CI |
|---|---|---|
| Day sleep (NSW) vs night sleep (DSW) | ||
| Dichotomous† | ||
| Evening | −53.2%‡ | (−61.1% to −45.3%) |
| Morning§ | −64.6%‡ | (−70.5% to −58.7%) |
| Trichotomous¶ | ||
| Evening | −51.3%‡ | (−60.8% to −41.7%) |
| Intermediate | −57.2%‡ | (−64.6% to −49.9%) |
| Morning§ | −71.2%‡ | (−77.5% to −64.9%) |
| Night sleep (NSW vs DSW) | ||
| Dichotomous† | ||
| Evening | −49.0%‡ | (−57.0% to −41.0%) |
| Morning§ | −30.0%‡ | (−40.9% to −19.1%) |
| Trichotomous¶ | ||
| Evening | −49.3%‡ | (−58.7% to −39.8%) |
| Intermediate | −38.5%‡ | (−48.4% to −28.6%) |
| Morning§ | −31.0%‡ | (−45.2% to −16.8%) |
| Night work (NSW) vs night sleep (DSW) | ||
| Dichotomous† | ||
| Evening | −73.2%‡ | (−77.5% to −69.0%) |
| Morning§ | −54.4%‡ | (−61.5% to −47.2%) |
| Trichotomous¶ | ||
| Evening | −76.2%‡ | (−80.5% to −71.8%) |
| Intermediate§ | −62.2%‡ | (−68.3% to −56.1%) |
| Morning§ | −51.0%‡ | (−61.0% to −41.0%) |
*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; referent category is all day shift workers (DSW); for example, in dichotomous analysis, evening type night shift workers during daytime sleep had 53.2% lower levels of 6-sulfatoxmelatonin than all day shift workers during night-time sleep.
†Evening: chronoscore 33 or less; morning: chronoscore 34 or higher.
‡p < 0.001, two-sided t test.
§Test for difference from evening-type category: p<0.01, using two-sided t test.
¶Evening: chronoscore 28 or less; intermediate: chronoscore 29–39; morning: chronoscore 40 or higher.