Researchers at Washington University School of Medicine in St. Louis say that a common drug prescribed for insomnia can help delay the onset of Alzheimer’s disease.
An inability to fall asleep and a disturbed sleep are very early signs of cognitive decline in people later diagnosed with Alzheimer’s down the line.
A very small two-night study by the University found that people who took a sleeping pill before going to bed experienced a drop in a Alzheimer-associated amyloid beta proteins. Higher levels of such proteins indicate worsening symptoms of the disease.
Suvorexant prescribed for insomnia might be helpful in slowing or stopping the progression of Alzheimer’s disease.
The study is published in the Annals of Neurology.
“This is a small, proof-of-concept study. It would be premature for people who are worried about developing Alzheimer’s to interpret it as a reason to start taking suvorexant every night,” said senior author Brendan Lucey, MD, an associate professor of neurology and director of Washington University’s Sleep Medicine Center.
The study is very nascent with no indication of how long-term usage of the drug will play out. Still, these results are very encouraging. This drug is already available and proven safe.
Alzheimer’s disease is diagnosed in people with high levels of plaques of the protein amyloid beta in the brain. A secondary brain protein, tau, builds up later that is toxic to neurons. People with Alzheimer’s disease start experiencing cognitive symptoms such as memory loss.
High levels of amyloid protein and Alzheimer’s
Lucey and colleagues found that poor sleep is linked to higher levels of both amyloid and tau in the brain. It is still not established fully yet if good sleep reduces amyloid and tau levels, and a halt in or reversal of the progress of Alzheimer’s disease. Some mouse studies with orexin inhibitors have been promising.
For their sleep study, Lucey and team recruited 38 participants ages 45 to 65 and with no cognitive impairments. The participants were given a lower dose (10 mg) of suvorexant (13 people), a higher dose (20 mg) of suvorexant (12 people) or a placebo (13 people) before bedtime at a sleep clinic.
Researchers withdrew a small amount of cerebrospinal fluid via spinal tap every two hours for 36 hours, starting one hour before the sleeping aid or placebo was administered, to measure how amyloid and tau levels changed over the next day and a half.
Amyloid levels dropped 10% to 20% in the cerebrospinal fluid of people who had received the high dose of suvorexant compared to people who had received a placebo, and the levels of a key form of tau known as hyperphosphorylated tau dropped 10% to 15%, compared to people who had received placebo. There was not much difference in people who received the low and high dosages of suvorexant.
24 hours later, hyperphosphorylated tau levels in the high-dose group had risen, while amyloid levels remained low. A second dose of suvorexant, administered on the second night, sent the levels of both proteins down again for people in the high-dose group. Placebo group did not show any downward slide.
“If we can lower amyloid every day, we think the accumulation of amyloid plaques in the brain will decrease over time,” Lucey said.
“And hyperphosphorylated tau is very important in the development of Alzheimer’s disease because it’s associated with forming tau tangles that kill neurons. If you can reduce tau phosphorylation, potentially there would be less tangle formation and less neuronal death.”
Studies to find long-term effects of sleep drug
The present study was too small. The research team is already undertaking bigger studies to assess the longer-term effects of orexin inhibitors (found in insomnia medicines) in people at higher risk of dementia.
“Future studies need to have people taking these drugs for months, at least, and measuring the effect on amyloid and tau over time,” Lucey said. “We’re also going to be studying participants who are older and may still be cognitively healthy, but who already have some amyloid plaques in their brains. This study involved healthy middle-aged participants; the results may be different in an older population.”
The team said that further studies are needed to come to any conclusion about the effects of the drug on amyloid and tau proteins but it is advisable to get a good night’s sleep to avoid any cognitive decline.