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Learning Objective 1: describe the performance of daytime functioning and changes in heart rate variability (HRV) in insomniacs.
Learning Objective 2: compare the difference in heart rate variability (HRV) and daytime functioning between insomniacs and normal sleepers.
Methods: All participants underwent an interview, a medical examination, and a sleep measurement protocol during which they wore an actigraph and logged a sleep diary for a 7-day period to verify their eligibility. Included in the study were 18 insomniacs and 21 normal sleepers. During a laboratory session, these participants completed 5 paper-pencil tests of sleepiness, anxiety, fatigue, and concentration difficulty, and the Wisconsin Card Sorting Test. Resting HRV was recorded under paced breathing.
Results: Neither did insomniacs experience cognitive impairment nor did they experience excessive daytime sleepiness compared with normal sleepers. However, insomniacs experienced higher frequency of fatigue (effect size [ES] =1.14, p = 0.002) compared with normal sleepers. There was a trend tower higher trait anxiety score (ES = 0.62) and concentration difficulty (ES = 0.59) in insomniacs than in normal sleepers. Although a trend toward lower resting high frequency (HF)-HRV (ES = -0.57) in insomniacs than in normal sleepers was noted, neither the resting low-frequency (LF)-HRV nor the LF/HF ratio were different between groups. Subjective sleep estimates correlated to self-reported daytime consequences such as fatigue and concentration difficulty but not cognitive function. On the contrary, objective sleep estimates correlated to problem-solving/conceptualization and learning but not self-reported daytime consequences.
Conclusions: Insomniacs are not sleepier during the day than normal sleepers. However, they may experience daytime symptoms such as fatigue and concentration difficulty although cognitive function remains unimpaired.