Are insomniacs sleepy during the day? A pupillometric assessment.

A biodevelopmental model of insomnia is articulated specifying coordinated nighttime (disturbed sleep pattern) and daytime (no excessive daytime sleepiness) characteristics defining an insomnoid classification in at-risk groups: short sleepers and older adults. Pupillometry is proposed as a useful means of discriminating degree of daytime sleepiness to aid in the differential diagnosis of insomnia and insomnoid states, and the present study tested the discriminative validity of this approach. Noninsomniac (n = 34) and insomniac (n = 29) college students submitted to four 10 min pupillometry sessions tracking daytime sleepiness from morning arising to bedtime. Pupil diameter proved to be an able discriminator of these two groups though substantial overlap of the two distributions was also noted. The results supported the sensitivity of pupillometry in detecting daytime sleepiness, but yielded alternative interpretations. We observed statistical differentiation in insomniac and noninsomniac daytime sleepiness, but substantial, functional overlap between these groups. Assessment and treatment implications arising from the biodevelopmental model were hypothesized.     

Vigilance, personality and strength of the nervous system

Numerous attempts have been made to explain the overall level of performance and the change in performance over time in vigilance tasks in terms of the proposed inverted U relationship between performance and ‘arousal’. The present experiment investigated the effects on vigilance performance of the following variables: introversion, neuroticism, time of day, accessory sensory stimulation, ‘signal frequency’ and time on task. Some measures of subjective state and body temperature were also included. The behavioural measures of overall performance revealed interactions involving neuroticism and time of day, and between neuroticism and frequency. This may reflect the operation of response bias factors, though these may be influenced by ‘arousal’. There were also main effects for several of the factors which may have practical significance. There was a significant effect of time on task on all the behavioural measures but no clearcut effects of personality on the vigilance ‘decrement’. It is argued that the latter may not provide the most satisfactory test of the inverted U model and its relationship to personality. However, interactions between noise and time on task for some of the measures may have practical importance. Measures of subjective state showed a fall in the reported level of ‘arousal’ accompanied by a rise in reported ‘stress’ and ‘anxiety’ with time on task. Body temperature was higher after the task than before.