Task switching in older adults with and without insomnia

Abstract Background Task-switching deficits are common in older adults and in those with insomnia. Such deficits may be driven by difficulties with sleep continuity and dampened homeostatic sleep drive. Objective To identify the aspects of task switching affected by insomnia and its treatment, and to determine whether such effects are associated with sleep continuity and homeostatic sleep drive. Methods Polysomnographic sleep and task switching were tested in healthy older adults aged 60–93 years with insomnia (n = 48) and normal sleeping controls (n = 51). Assessments were repeated in the insomnia group after eight weeks of cognitive behavioral treatment for insomnia. Sleep measures included wake after sleep onset (WASO) and quantitative indices of homeostatic sleep drive (delta power during nonrapid eye movement [NREM] sleep and the ratio of delta power during the first and second NREM periods). A cued task-switching paradigm instructed participants to perform one of two tasks with varying preparatory cue-target intervals, manipulating task alternation, task repetition, and task preparation. Results The effect of preparatory cues on accuracy was diminished in the insomnia group compared with that in controls. Across the two groups, a stronger effect of preparatory cues was associated with a higher delta sleep ratio. Following insomnia treatment, task-repetition accuracy significantly improved. This improvement was associated with improvements in WASO. There were no group or treatment effects on response time or task alternation accuracy. Conclusions Effects of insomnia diagnosis and treatment apply to conditions that depend on the maintenance of a task set, rather than a domain general effect across task switching. Such effects are associated with homeostatic sleep drive and sleep continuity.