Table 3. Results from regression analyses of melatonin and cortisol levels within the night shift workers (n=185 urinary measurements and 182 serum measurements) during daytime sleep or nighttime work, relative to nighttime sleep.

Comparison†	% higher (+) or lower (-) hormone levels, relative to nighttime sleep levels‡	95% Confidence Interval
Daytime sleep, relative to nighttime sleep
Urinary 6-Sulfatoxymelatonin (ng/mg creatinine)	-28.7%*	(-44.5%, -13.1%)
Urinary cortisol (ng/mg creatinine)	+28.9%*	(+11.5%, +46.4%)
Nighttime work, relative to nighttime sleep
Urinary 6-Sulfatoxymelatonin (ng/mg creatinine)	-37.5%**	(-45.7%, -29.2%)
Urinary cortisol (ng/mg creatinine)	+15.3%*	(+4.1%, +26.6%)
Serum cortisol, morning (μg/dL) §	-24.6%**	(-32.7%, -16.6%)

^*p<0.01, using two-sided t-test

^**p<0.0001, 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