Psychomotor performance decrements following a successful physical activity intervention for insomnia

Evidence supports the view that reductions in cognitive hyperarousal contribute substantially to improved sleep outcomes following cognitive and behavioral interventions for insomnia disorder. Assuming an inverted-u relationship between arousal and performance, a theoretical possibility, supported by limited empirical data, is that the same mediating processes could negatively impact aspects of psychomotor performance, reducing speed on tests of reaction time. Sedentary participants (mean age = 59.8; SD = 9.46) meeting research diagnostic criteria for insomnia were randomized to either an exercise intervention of ≥150 min of moderate-intensity activity per week (n = 20), or a wait-list control group (n = 21). Of these, n= 17 intervention and n=18 control participants completed 6-month follow-up assessments. Digit span, and simple and complex vigilance task performance was assessed using a computerized protocol at baseline and 6-month follow-up. Dependent variables included digit span, simple reaction time (SRT), complex reaction time (CRT), false positive responses, number of lapses, and SRT/CRT ratio (indicative of the magnitude of difference between simple and complex RT performance). The primary clinical outcome was Insomnia Severity Index (ISI) score. In comparisons of baseline to follow-up change, ISI scores showed clinically significant improvement in the intervention group at 6-month follow-up (F (8,26) = 5.16; P = 0.03). Baseline vigilance performance was equivalent in both groups. At 6-month follow-up, however, the intervention group showed significantly slower simple reaction time F(4,30)=10.25, p<0.01, and a significantly decreased SRT/CRT ratio (F(4,30)=13.22, p<0.01). Among people meeting diagnostic criteria for insomnia, beneficial sleep outcomes following successful behavioral interventions may, under some circumstances, come at the cost of slower psychomotor performance.