When the body’s biological clock goes awry, insomnia and related disruptions may be an early sign of pending cognitive decline, reports Scientific American.

Even when the underlying diagnosis is not RBD, people with neurodegenerative diseases suffer from a wide range of sleep-related problems, including insomnia, interrupted sleep and excessive daytime sleepiness. Researchers have long thought such disturbances were consequences rather than causes of brain pathology—either a direct result of degeneration of sleep regions in the brain, side effects of a particular drug regimen or other triggers. But many now suspect the relationship may be more complex.