New research suggests individuals with insomnia fail to cognitively disengage at night due to a delayed mental activity peak, pointing to potential circadian-based treatments.
Key takeaways:
- In a controlled lab study, older adults with insomnia failed to “downshift” their cognitive state from daytime problem-solving to nighttime disengagement as strongly as healthy sleepers.
- The cognitive activity peak in the insomnia group was delayed by approximately 6.5 hours, suggesting their internal clocks promote alert thinking later into the night.
- The findings indicate that cognitive hyperarousal in insomnia may stem from underlying circadian rhythm abnormalities rather than being solely a behavioral issue.
- Researchers propose that interventions targeting circadian rhythms, such as timed light exposure and structured routines, could complement existing insomnia treatments.
A new study published in Sleep Medicine suggests that chronic insomnia may be linked to disruptions in the brain’s natural 24-hour rhythm of mental activity, causing cognitive patterns to remain more “daytime-like” during nighttime hours.
The research, led by the University of South Australia (UniSA), is the first to map how cognitive activity fluctuates across a full day in individuals with chronic insomnia compared to healthy sleepers under controlled conditions designed to isolate the brain’s internal rhythms.
To examine the role of circadian abnormalities in cognitive hyperarousal, researchers monitored 32 older adults—16 with insomnia and 16 healthy sleepers—over 24 hours of wakeful bedrest. This protocol eliminated environmental and behavioral cues by keeping participants awake in a dimly lit room with controlled food and activity. Participants completed hourly checklists to assess the tone, quality, and controllability of their thoughts.
While both groups exhibited clear circadian patterns in mental activity, with peaks in the afternoon and troughs in the early morning, the insomnia group showed significant differences.
“Unlike good sleepers, whose cognitive state shifted predictably from daytime problem-solving to nighttime disengagement, those with insomnia failed to downshift as strongly,” says lead researcher Kurt Lushington, PhD, MPsych, a professor at UniSA, in a release. “Their thought patterns stayed more daytime-like in the nighttime hours when the brain should be quietening.”
The study found that the cognitive peaks for participants with insomnia were delayed by about 6.5 hours, indicating their internal clocks may encourage alert thinking well into the night.
“Sleep is not just about closing your eyes,” Lushington says. “It’s about the brain disengaging from goal-directed thought and emotional involvement. Our study shows that in insomnia, this disengagement is blunted and delayed, likely due to circadian rhythm abnormalities. This means that the brain doesn’t receive strong signals to ‘power down’ at night.”
These findings point to new treatment possibilities beyond current behavioral strategies. Co-author Jill Dorrian, PhD, a professor at UniSA, says interventions that strengthen circadian rhythms may be beneficial.
“These include timed light exposure and structured daily routines that may restore the natural day-night variation in thought patterns,” Dorrian says, in a release. “Practising mindfulness may also help quieten the mind at night.”
The study, “Cognitive-affective disengagement: 24-hour rhythm in insomniacs versus healthy good sleepers,” suggests that tailored approaches addressing both circadian and cognitive factors could offer a more targeted solution for insomnia.
