Objective: To examine psychomotor (reaction time) performance deficits and their relation to subjective and objective sleep measures among individuals with primary insomnia (PI).
Design and setting: This study was conducted at affiliated VA and academic medical centers using a matched-groups, cross-sectional research design.
Participants: Seventy-nine (43 women) individuals with PI (MAge = 50.0 +/- 17.1 y) and 84 (41 women) well-screened normal sleepers (MAge = 48.6 +/- 16.8 y).
Methods and measures: Participants underwent 3 nights of polysomnography (PSG) followed by daytime testing with a 4-trial multiple sleep latency test (MSLT). Before each MSLT nap, they rated their sleepiness and completed a performance battery that included simple reaction time (SRT), continuous performance (CPT), and 4 switching attention (SAT) tests. Performance measures included the mean response latency and the standard deviation of each subject's within-test response latencies.
Results: PI sufferers reported greater (P = 0.001) daytime sleepiness, but were significantly (P = 0.02), more alert than normal sleepers on the MSLT. Multivariate analyses showed the PI group had significantly longer response latencies and greater response variability across many of the subtests than did the controls. Regression analyses showed that both PSG- and diary-based sleep measures contributed to the prediction of daytime performance indices, although objective wake time after sleep onset appeared the best single predictor of the daytime measures.
Conclusions: Results confirm that PI sufferers do show relative psychomotor performance deficits when responding to challenging reaction time tasks, and these deficits appear related to both objective and subjective sleep deficits. Findings support PI patients' diurnal complaints and suggest the usefulness of complex reaction time tasks for assessing them.