Cognitive-affective disengagement: 24h rhythm in insomniacs versus healthy good sleepers

This study explored whether a failure to down-regulate cognitive-affective activity at night in insomniacs reflect the presence of underlying circadian rhythm abnormalities. 16 sleep maintenance insomniacs (11 F; 64.3 ± 7.2 y) and 16 good sleepers (11 F; 65.4 ± 7.4 y) participated in a constant routine protocol involving 24 h of wakeful bedrest, which controls for any conditioned response to sleep initiation. Every hour participants completed a cognitive-affective disengagement checklist containing four items assessing the tone and quality of mentations and four items assessing metacognitive activity. Circadian rhythmicity and group differences were tested using cosinor analyses. Except for thought modality (mental activity was auditory vs imagery) and thought structure (mental activity was repetitive vs sequential) in insomniacs, the remaining tone and quality of mentations and all metacognitive measures demonstrated circadian rhythmicity in both insomniacs and good sleepers. However, insomniacs compared to good sleepers demonstrated less 24 h variation (smaller amplitude) in reality orientation (mental activity was dream-like vs real-like), volitional control (little vs much control over mental activity) and thought structure; and reflective of continuing cognitive engagement, a greater tendency for sequential mental activity at night (higher mesor). Our findings are consistent with the hyperarousal model of insomnia, with the failure to downregulate prefrontal activity at night leading to greater goal-oriented processing and less cognitive-affective disengagement. Strengthening the circadian rhythmicity of cognitive-affective activity and modifying sequential thinking are potential interventions in the future treatment of insomnia.