New study explains why some people struggle to ‘switch off’ at night

Published in Sleep Medicine, the study led by the University of South Australia (UniSA) is the first to map how cognitive activity fluctuates across the day in individuals with chronic insomnia, compared to healthy sleepers.

Insomnia affects around 10 percent of the population, and up to 33 percent of older adults, with many reporting an overactive or racing mind at night. While this has long been associated with cognitive hyperarousal, its underlying causes have remained unclear.

The researchers examined whether the inability to reduce mental activity at night – a core feature of insomnia – reflects circadian rhythm abnormalities. Under tightly controlled laboratory conditions, 32 older adults were monitored (16 with insomnia and 16 healthy sleepers) over 24 hours of wakeful bedrest.

This approach eliminated environmental and behavioural cues, allowing scientists to isolate the brain’s internal rhythms. Participants remained awake in a dimly-lit room, in bed, with food and activity carefully controlled. They completed hourly checklists, assessing the tone, quality and controllability of their thoughts.

Both healthy sleepers and those with insomnia displayed clear circadian patterns in mental activity, peaking in the afternoon and dipping in the early morning. However, several key differences emerged in the insomnia group.

“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. “Their thought patterns stayed more daytime-like in the night-time hours when the brain should be quietening.”

Their cognitive peaks were also delayed by around six and a half hours, suggesting that their internal clocks may encourage 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.”

“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.”

Co-author, UniSA Professor Jill Dorrian, said the findings highlight new treatment possibilities for insomniacs, such as interventions that strengthen circadian rhythms.

“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 may also help quieten the mind at night.”

The researchers say that current treatments often focus on behavioural strategies, but these findings suggest that tailored approaches addressing circadian and cognitive factors could offer a solution.

Earlier, Qazinform  News Agency reported that speaking more than one language may help keep the brain young, according to a large European study of over 80,000 people. Published in Nature Aging this month, the research found that multilinguals were about half as likely to show signs of accelerated biological ageing as those who spoke only one language.