New research has shed light on why the elderly have trouble falling and staying asleep, and have a tendency to wake up too early the next morning. This burdensome symptom is particularly pronounced in those suffering from Alzheimer’s, which can lead to nighttime wandering and disorientation.

Researchers at Beth Israel Deaconess Medical Center (BIDMC) and the University of Toronto/Sunnybrook Health Sciences Center discovered that a specific group of inhibitory neurons in the brain are significantly diminished in old age, which can cause sleep disruption.

Sleep problems are much more common in the elderly compared to younger people. A healthy 70 year old can wake up at least four times per night without any underlying disease associated with such sleep disruption.

Senior study author Clifford B. Saper, MD, PhD, Chairman of Neurology at BIDMC and James Jackson Putnam Professor of Neurology at Harvard Medical School, first discovered in 1996 that the ventrolateral preoptic nucleus was acting as a “sleep switch” in lab rats, which affected their ability to fall asleep. The animals with such reduced neurons slept only 50 percent as much as the normal amount, with their remaining sleep being disrupted.

The intermediate nucleus in the brain is positioned in a similar location as in the lab rats, and features the same inhibitory neurotransmitter, galanin. The researchers believed that if there was any similarity between the role of the intermediate nucleus in humans and the vetrolateral preoptic nucleus in the lab rats, then there would be a similar sleep disruption in humans.

“On average, a person in his 70s has about one hour less sleep per night than a person in his 20s. 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,” said Saper in a statement.

The findings of the study are published in the journal Brain.