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In patients with Alzheimer disease (AD), increased cerebrospinal fluid levels of orexin, which helps regulate the sleep-wake cycle, may lead to sleep deterioration, according to a new study. The condition also appears to be associated with cognitive decline. 

AD is a neurodegenerative disease which can lead to progressive memory loss and cognitive decline. The disease is also often complicated by sleep disturbance. 

Patients with moderate to severe AD presented with higher average orexin levels compared with controls and they had more impaired sleep compared with controls and patients with mild AD, the press release added.

Researchers noted that in the overall AD group, orexin levels were associated with total tau protein levels and sleep impairment. Cognitive impairment was also associated with sleep deterioration. 

"Our study has shown that, in AD, increased CSF orexin levels are linked to a parallel sleep deterioration, which appears to be related to cognitive decline. Hence, our results demonstrate that, in AD, orexinergic output and function seem to be overexpressed with disease progression and severity, possibly owing to an imbalance in the neurotransmitter networks regulating the wake-sleep cycle toward the orexinergic system promoting wakefulness," said researchers in the press release. 

The study has been released in the journal JAMA Neurol.