ABSTRACT
Sleepiness is an awake condition that is associated with an increased tendency to fall asleep. For many years, the measurement of sleepiness has remained a challenge for sleep clinicians and researchers alike. This topic is so significant that it has even warranted consideration as the possible “holy grail of sleep medicine.” (1). There are many challenges in the clinical assessment of sleepiness. To start with, sleepiness is frequently confused with fatigue, which refers to a lack of physical energy and a sense of exhaustion following physical activity. Second, we have the issue of subjective underestimation of sleepiness by those who are excessively sleepy. Third, can data from neurophysiological and neuropsychological studies obtained from sleep deprivation experiments in healthy subjects be extrapolated to sleepiness due to actual sleep disorders? Further, the correlation between subjective (questionnaires) and objective measures of sleepiness [multiple sleep latency test (MSLT)/maintenance of wakefulness test (MWT)] is suboptimal. Finally, physiological measurements obtained in the quiet environment of the sleep laboratory may not be representative of sleepiness encountered in day-to-day, real-life situations like driving or desk work. These shortcomings notwithstanding, a substantial body of information has been gathered on the measurement of sleepiness, a synopsis of which is presented hereunder.
