Table 2. Results from regression analyses of melatonin and cortisol levels between night shift workers (NSW), relative to day shift workers (DSW), all participants (n=158 day and 185 night shift workers).

Comparison†	% higher (+) or lower (-) NSW hormone levels, relative to DSW levels‡	95% Confidence Interval
Day sleep (NSW), relative to night sleep (DSW)
Urinary 6-Sulfatoxymelatonin (ng/mg creatinine)	-57.5%*	(-66.1%, -48.9%)
Urinary cortisol (ng/mg creatinine)	+15.7%**	(+1.0%, +30.3%)
Night work (NSW), relative to night sleep (DSW)
Urinary 6-Sulfatoxymelatonin (ng/mg creatinine)	-62.0%*	(-69.0%, -55.0%)
Urinary cortisol (ng/mg creatinine)	+3.3%	(-9.0%, +15.7%)
Serum cortisol, morning (μg/dL) §	-42.7%*	(-49.5%, -35.8%)
Off-night sleep (NSW), relative to night sleep (DSW)
Urinary 6-Sulfatoxymelatonin (ng/mg creatinine)	-39.8%*	(-50.5%, -29.1%)
Urinary cortisol (ng/mg creatinine)	-12.7%**	(-24.4%, -0.9%)
Serum cortisol, morning (μg/dL) §	-24.4%*	(-32.7%, -16.0%)

^*p<0.0001, using two-sided t-test

^**p<0.05, using two-sided t-test

^†Analyzed using the natural log transformation

^‡Adjusted for the effects of age, hours of darkness, body mass index, number of alcoholic beverages consumed, nicotine/tobacco consumption, and use of medications specified a priori

^§Single serum sample collected within approximately 90 minutes of rising from night sleep or completing the night shift