SLEEPINESS AS MEASURED BY MODIFIED MULTIPLE SLEEP LATENCY TESTING VARIES AS A FUNCTION OF PRECEDING ACTIVITY

Many studies have examined the impact of varying levels of sleep loss or sleep disturbance upon the multiple sleep latency test (MSLT). Virt ually no studies have examined the impact of level of physiologic arou sal upon measured sleep tendency. In the current study, 12 normal-slee ping young adults took modified multiple sleep latency tests after eit her watching television for 15 minutes or after a 5-minute walk. This entire protocol was repeated on another week after subjects had been p artially sleep deprived by reducing their time in bed by 50%. it was h ypothesized that sleep latencies would be significantly shorter after watching television as compared to walking and after partial sleep los s as compared to normal sleep and that these effects would be independ ent. The results of the study supported ail of these hypotheses. ANOVA s showed no significant interaction effects, but steep latencies were 11.6 and 5.8 minutes following the walk and watching television respec tively. Sleep latencies were 9.8 and 7.6 minutes following baseline an d partial sleep-deprivation conditions. Heart rate, used as a measure of physiological arousal, was significantly elevated throughout naps f ollowing the walk as compared to naps following television viewing. On a theoretical level, these data imply that measured sleepiness is a c ombination of sleep drive and physiological arousal, and these effects appear to be independent. On a practical level, these data indicate t hat more care may be necessary in monitoring the activity levels of pa tients and subjects prior to MSLT evaluations, since physiological aro usal may mask the measurement of sleep tendency. Knowledge of the role of arousal in modulating sleepiness can be important in many settings .