Being awake at night and dozing during the day can be a distressing early symptom of Alzheimer’s disease, but how the disease disrupts our biological clocks to cause these symptoms has remained elusive.

Now, scientists from Cambridge have discovered that in fruit flies with Alzheimer’s the biological clock is still ticking but has become uncoupled from the sleep-wake cycle it usually regulates. The findings – published in Disease Models & Mechanisms – could help develop more effective ways to improve sleep patterns in people with the disease.

People with Alzheimer’s often have poor biological rhythms, something that is a burden for both patients and their carers. Periods of sleep become shorter and more fragmented, resulting in periods of wakefulness at night and snoozing during the day. They can also become restless and agitated in the late afternoon and early evening, something known as ‘sundowning’.

Biological clocks go hand in hand with life, and are found in everything from single celled organisms to fruit flies and humans. They are vital because they allow organisms to synchronise their biology to the day-night changes in their environments.