Individuals experiencing difficulty falling asleep might predispose themselves to cognitive decline in their later years, as scientists featured in the journal Neurology indicate.

"People who have more disrupted sleep in their 30s and 40s may be more likely to have memory and thinking problems a decade later," they warned.

"Growing evidence supports an association between sleep quality and risk of dementia," the team added.

Their work covered over 500 people who were tracked for 11 years. While they conceded it did not prove sheep-counters in their 30s would end up with cognition problems when they get old, they said there was "an association," which appears to be based more on how deeply a person sleeps rather than for how long.

"Our findings indicate that the quality rather than the quantity of sleep matters most for cognitive health in middle age," said author Yue Leng of the University of California, San Francisco.

"Understanding the connection between sleep and cognition earlier in life is critical for understanding the role of sleep problems as a risk factor for the disease," she said.

Poor sleep is sometimes caused by sleep apnea, which briefly wakes the sufferer dozens of times a night, usually without him or her being aware of it.

In May 2023, the journal Annals of Internal Medicine published results of tests showing sleep apnea as, unsurprisingly, leading to "excessive daytime sleepiness." That followed Neurology and Frontiers in Sleep releasing papers that showed links between sleep apnea and the likelihood of cognitive decline in old age. Other recently published research has posited a link between restless late nights and the risk of developing diabetes.