WASHINGTON -- New research is shedding light on why older people have more trouble sleeping.
A study from Beth Israel Deaconess Medical Center and the University of Toronto/Sunnybrook Health Sciences Center -- for the first time -- found a neurological reason for the loss of sleep.
When older people and people with Alzheimer's disease lose a specific group of neurons in their brains, the result is a lack of sleep or fragmented sleep.
"On average, a person in his 70s has about one hour less sleep per night than a person in his 20s," senior author Dr. Clifford B. Saper, chairman of Neurology at BIDMC and James Jackson Putnam Professor of Neurology at Harvard Medical School, said in a news release.
The lack of sleep can translate to more serious health issues. It can contribute to Alzheimer's disease, dementia and ailments such as type 2 diabetes, high blood pressure and vascular disease.
A key group of neurons, known as the ventrolateral preoptic nucleus, serves as a "sleep switch."
"It now appears that loss of these neurons may be contributing to these various disorders as people age," Saper said in the release.
Researchers studied rats and found that the loss of neurons over time produced insomnia "with animals sleeping only about 50 percent as much as normal and their remaining sleep being fragmented and disrupted," Saper said.
In order to test this hypothesis, the investigators analyzed data from the Rush Memory and Aging Project -- a study of aging and dementia with about 1,000 people. The participants entered the study when they were 65-year-old and the study followed them until death. Their brains were donated to the study after death.
"We found that in the older patients who did not have Alzheimer's disease, the number of ventrolateral preoptic neurons correlated inversely with the amount of sleep fragmentation," Saper said. "The fewer the neurons, the more fragmented the sleep became."
In people who died of Alzheimer's, researchers found those who lost the most neurons had the most disrupted sleep.
The research published in the journal Brain may lead to new ways or medications to diminish sleep problems in older people and to medications to help Alzheimer's patients sleep through the night.
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