Having a proper, restful sleep tends to get harder as people age. In a new study, a team of researchers has shed light on how "hyperexcitable neurons" may be behind the sleep problem.

Different age groups have different sleep needs, and it's recommended that adults get seven or more hours of sleep per night. However, getting a good night's sleep can become harder with age.

While there are some possible explanations for why this happens, the "mechanistic underpinnings of sleep instability remain elusive," the authors of a new study, published in the journal Science, said.

"Therefore, understanding why the aging brain fails to consolidate sleep may shed light on translational applications for improving the sleep quality of aged individuals," the researchers wrote.

The sleep problem that comes with age isn't limited to humans as it has also been observed in other species.

Previously, one of the study authors, Professor Luis de Lecea of Stanford University, and his colleagues found that key brain neuropeptides, known as hypocretins (Hcrt), transmit signals that are "vital" in stabilizing wakefulness. Hypocretins are produced only by about 50,000 neurons in the brain, AFP News reported.

Previous studies found that "degradation" in hypocretins contributes to narcolepsy in humans, dogs and mice. Narcolepsy is a sleep disorder that's characterized by "overwhelming daytime drowsiness" and "sudden attacks of sleep," the Mayo Clinic explained.

"We hypothesized that the decline in sleep quality could be due to malfunction of the neural circuits associated with sleep/wake control," the researchers wrote. "In this study, we investigated whether the intrinsic excitability of Hcrt neurons is altered, leading to a destabilized control of sleep/wake states during aging."

The researchers used mice models for their work. They found that indeed, the older mice had sleep fragmentation and that they experienced "significant loss" of hypocretin neurons. However, the aged Hcrt neurons were "hyperexcitable," having a "more frequent firing pattern" that resulted in disruptions in sleep continuity and caused wake bouts in the aged mice.

"The neurons tend to be more active and fire more, and if they fire more, you wake up more frequently," Lecea explained, as per AFP News.

"These results suggested that hyperexcitability of Hcrt neurons emerges with age," the researchers wrote.

The find is relevant since losing sleep doesn't just mean not having enough rest. Sleep issues can also contribute to mental and physical health problems down the line, the researchers noted. And while many people use a class of drugs called hypnotics to treat insomnia, this often doesn't work as well in older people.

With the findings, new therapies that target this mechanism may help those suffering from the problem finally get a good night's sleep