Insomnia Linked To Disruptions In Circadian Rhythm Of Mental Activity, Study Finds

Australian researchers have discovered a potential link between insomnia and disruptions in the brain's natural 24-hour rhythm. This finding may explain why some individuals find it difficult to 'switch off' at night. The study, published in Sleep Medicine and led by the University of South Australia (UniSA), is the first to map how cognitive activity varies throughout the day in people with chronic insomnia compared to healthy sleepers.

Insomnia affects about 10% of the population, with up to 33% of older adults experiencing it. Many report having an overactive or racing mind at night. While this has been associated with cognitive hyperarousal, its underlying causes have remained unclear. The researchers aimed to determine if the inability to reduce mental activity at night, a core feature of insomnia, reflects circadian rhythm abnormalities.

The study involved monitoring 32 older adults under controlled laboratory conditions for 24 hours of wakeful bedrest. This group included 16 individuals with insomnia and 16 healthy sleepers. The controlled environment eliminated external cues, allowing scientists to focus on the brain's internal rhythms. Participants stayed awake in a dimly-lit room, with food and activities carefully regulated.

Both groups displayed clear circadian patterns in mental activity, peaking in the afternoon and dipping early in the morning. However, significant differences were observed among those with insomnia. "Unlike good sleepers, whose cognitive state shifted predictably from daytime problem-solving to nighttime disengagement, those with insomnia failed to downshift as strongly," said lead researcher UniSA Professor Kurt Lushington.

The study found that individuals with insomnia had delayed cognitive peaks by around six and a half hours. This suggests their internal clocks may promote alert thinking well into the night. "Sleep is not just about closing your eyes," Prof Lushington stated. "It’s about the brain disengaging from goal-directed thought and emotional involvement."

The findings indicate that in insomnia, this disengagement is blunted and delayed due to circadian rhythm abnormalities. As a result, the brain doesn't receive strong signals to 'power down' at night.

Potential New Treatments for Insomnia

Co-author UniSA Professor Jill Dorrian highlighted new treatment possibilities for insomniacs based on these findings. Interventions that strengthen circadian rhythms could be beneficial. "These include timed light exposure and structured daily routines that may restore the natural day-night variation in thought patterns," Prof Dorrian said.

Practising mindfulness might also help quieten the mind at night. Current treatments often focus on behavioural strategies, but these findings suggest tailored approaches addressing circadian and cognitive factors could offer a solution.

This research provides valuable insights into understanding insomnia's complexities and opens avenues for developing more effective treatments targeting both circadian rhythms and cognitive processes.

With inputs from WAM