Relationship between sleep efficiency and urinary excretion of catecholamines in bed-rested humans

The relationship between urinary excretion of catecholamines during sleep and sleep disturbance was examined in four healthy subjects who were confined to bed for approximately 1 week under an entrained condition. Polysomnographic recordings were made throughout the period of continuous bed rest. Free epinephrine and norepinephrine excretion were measured. Sleep efficiency, i.e., percentage of total sleep time over an allotted sleep period, was an indicator of sleep disturbance. All subjects showed a negative correlation between sleep efficiency and epinephrine excretion (average correlation coefficient -0.79, p less than 0.004). Norepinephrine excretion correlated negatively with sleep efficiency in only one subject, and the group average correlation coefficient of -0.28 was not significant. Circadian variations were observed in sleep efficiency and catecholamine excretion. Although epinephrine excretion was influenced by psychophysiological stress arising from the experimental conditions of forced bed rest, the correlation between sleep efficiency and epinephrine excretion remained stable and negative. The urinary excretion of epinephrine could be an effective indicator of sleep disturbance.