Subjective sleepiness and executive functions over a 14‐hour wake period in elderly subjects

Objectives/Introduction: Although many clinical studies point to excessive daytime sleepiness as a common complaint in aging (e.g., Ohayon and Vecchierini, 2002), systematic data on the time‐course of elderlies’ vigilance levels over daytime wake period are surprisingly sparse. A few data have been produced on elderly individuals’ subjective sleepiness and on its associations with objective behavioural signals, such as yawning and blink rate (Zilli et al., 2008; De Padova et al., 2009) as well with simple reaction times (Hoch et al., 1992), whereas the relationships between subjective sleepiness and more complex performance measures have still to be clarified. Therefore, the aim of this study is to trace the time‐course of subjective sleepiness and of executive functioning (namely, the inhibition capacity) over a 14‐hr wake period in an aged population. Methods: Fortysix elderly subjects (M = 18, F = 28, age 78.0 ± 7.6 years.) were monitored over a 14‐hr period for: (a) subjective daytime sleepiness, through a 5‐point Likert sleepiness scale administered every hour from 8:30 to 22:30; (b) executive inhibition function, by means of a Go‐noGo task that the subjects were instructed to perform at four times (8:00, 11:30, 16:00 and 21:00), with omissions (lapses at the Go stimuli) and false alarms (responses to the noGo stimuli) as dependent variables. Results: A significant effect of “time of day” was found for subjective sleepiness (F = 22.6, p < 0.0001), accounted for, as shown by post‐hoc contrasts, by the higher values at the post‐prandial dip (14:30 and 15:30 measurements) and in the evening hours (21:30 and 22:30 measurements) relative to all other times. The absolute values of subjective sleepiness never exceeded the moderate score of 3.1 on the Likert scale.Instead, no significant effect of “time of the day” was found for objective measures, both for omission (F = 1,18, ns) and inhibition capacity (F = 1,74, ns). Conclusions: Repeatedly and systematically measured across the whole wake period, our aged population's vigilance seems strikingly preserved, showing an overall level and a diurnal time course comparable to those described at previous ages. Interestingly, there is no significant variation across daytime of complex performance, suggesting that this variable is partly irrespective of vigilance levels’ fluctuations.