Difficulty “switching off” at night may be tied to disruptions in the brain’s natural 24-hour cycle of mental activity.
A study led by the University of South Australia (UniSA) – and reported by SciTechDaily – offers new insight into insomnia, mapping how cognitive activity fluctuates throughout the day for those with the condition, compared to healthy sleepers.
One in 10 people in the general population experiences insomnia, a figure that jumps to one in three older adults, many of whom report struggling with an overactive or “racing” mind at night. Although long linked to cognitive hyperarousal – a state in which senses heighten and thoughts and emotions go into overdrive – it remained unclear where these thought patterns stemmed from.
For this new study, published in Sleep Medicine, researchers looked at whether this inability to wind down at night reflected underlying circadian rhythm abnormalities. They monitored 16 older adults with insomnia and 16 without under tightly controlled laboratory conditions, eliminating external cues in order to isolate the brain’s internal rhythms.
Participants spent 24 hours under “wakeful bedrest,” staying awake in a dimly lit room with food and activity carefully controlled. Each hour they completed checklists, assessing the tone, quality and controllability of their thoughts.
[See more: Unhealthy sleep could be prematurely ageing your brain, study finds]
While both groups displayed clear circadian patterns in mental activity, peaking in the afternoon and dipping in the mornings, clear differences emerged among the insomniacs.
“Unlike good sleepers, whose cognitive state shifted predictably from daytime problem-solving to nighttime disengagement, those with insomnia failed to downshift as strongly,” lead researcher Professor Kurt Lushington explained in a press release. “Their thought patterns stayed more daytime-like in the night-time hours when the brain should be quietening.”
The insomnia group also experienced a delay in cognitive peaks of around six and half hours, indicating that their internal clocks may be keeping their minds active far later than healthy sleepers.
Sleep requires “the brain disengaging from goal-directed thought and emotional involvement,” Lushington said. “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.”
The findings suggest that, rather than the behaviour-focused strategies currently employed to treat insomnia, patients may benefit more from tailored approaches addressing circadian and cognitive factors.
