London - Elderly people may struggle to sleep as well as they did during their youth because they start to lose part of the brain that helps them “switch off”, scientists believe.
Researchers have identified a group of cells which blocks off conscious thoughts, allowing us to sleep.
They think these inhibitory neurons are gradually eroded as we age, leading to greater sleep problems in later life.
The scientists, from Harvard Medical School in the US, suggested the same process is seen in people with Alzheimer’s disease, who are particularly prone to disrupted sleep and night-time confusion.
Professor Clifford Saper, who led the research published in the journal Brain, said: “On average, a person in his 70s has about one hour less sleep per night than a person in his 20s.
“The loss of these neurons with ageing and with Alzheimer’s disease may be an important reason why older individuals often face sleep disruptions.
“These results may therefore lead to new methods to diminish sleep problems in the elderly.”
He added: “Sleep loss and sleep fragmentation is associated with a number of health issues, including cognitive dysfunction, increased blood pressure and vascular disease, and a tendency to develop type 2 diabetes.
“It now appears that loss of these neurons may be contributing to these various disorders as people age.”
Professor Saper’s team discovered a group of neurons – the ventrolateral preoptic nucleus – was functioning as a sleep switch in rats. They then found the same process was happening in humans. The cells turned off the brain’s arousal systems to enable the animals to fall asleep.
Professor Saper said: “Our experiments in animals showed that loss of these neurons produced profound insomnia, with animals sleeping only about 50 percent as much as normal and their remaining sleep being fragmented and disrupted.” A group of inhibitor cells in the human brain is found in a similar location and has the same chemical make-up as that found in rats.
The researchers analysed data from 45 elderly people who had donated their brains to science and had agreed to wear movement sensors to monitor how well they slept, from the age of 65 until their death at an average age of 89.
Examining the brains, the scientists found people with fewer neurons in the “sleep switch” area were more likely to have sleepless nights.
Professor Saper said: “The fewer the neurons, the more fragmented the sleep became.”
For those with the fewest inhibitor cells, less than 40 per cent of their time in bed was spent in extended periods of sleep. - Daily Mail