Alzheimer’s disease (AD) is most often associated with memory problems, but sleep problems can manifest much earlier and may hint at the progress of AD. While suggestions abound that disrupted sleep promotes AD, scientists from the University of California San Francisco (UCSF) in US have found that specific tangles of brain proteins associated with AD directly attack brain regions that keep us awake during the day.

An analysis of postmortem brain tissues of select AD patients showed that the degeneration of wake-promoting neurons was related to significant buildup of brain-harming proteins – as many as 75% of neurons was lost in a complex brain system. In addition, the neuropeptide orexin, which plays a crucial role in wakefulness, was practically annihilated in the brains of AD patients – the neurons producing orexin had decreased by more than 71%. An experiment in mouse models, then, evoked similar symptoms to human narcolepsy – a chronic sleep disorder characterised by daytime drowsiness.

UCSF’s Jun Oh, who researches memory and ageing, said the degeneration of a whole wakefulness-promoting network indicates that the brain resorts to sleep dysfunction as an extreme measure.

Similarly, Lea Grinberg, a neurologist and pathologist at UCSF, said that the study supports the idea that sleep dysfunction is a manifestation of Alzheimer’s pathology, thanks to unmitigated protein buildup in the brain.She adds, “It opens opportunities to treat the cause rather than the symptoms.”

The scientists are now examining if excessive napping can lead to earlier and more effective Alzheimer’s diagnosis.