Alzheimer's disease is a progressive disease that can takes years or decades to fully develop before symptoms appear. A potential early warning sign of Alzheimer’s disease now being explored is a connection with poor sleep patterns caused by disruptions to the biological clock’s circadian rhythm.
Disturbances in the circadian rhythm are linked to an increased risk of metabolic disease and inflammation – factors also linked to neural damage. As the circadian rhythm is further disturbed, fragmented sleep marked by changes in the sleep-wake cycle are seen and these changes are also seen in Alzheimer’s disease.
So could disruption in the circadian rhythm be a very early sign of Alzheimer’s disease? To explore this, researchers followed the sleep cycles of 189 healthy adults with an average age of 66 years with no signs of cognitive impairment. They also did brain imaging to look for amyloid protein build-up in the brain – a key hallmark for the presence of Alzheimer’s disease.
Most of the people had normal sleep cycles and no signs of amyloid protein build-up. But for the 50 people identified with evidence of amyloid protein build-up, disruption of their body clocks was a common feature. For those people, they were still getting adequate sleep, but it was fragmented with cycles of sleeping and waking.
The big question is which comes first? Do poor sleep patterns lead to amyloid protein build-up or do brain changes from early stage Alzheimer’s disease result in trouble sleeping? Scientists don’t have an answer to this yet, but it is possible that both are related to each other. Good quality sleep is important for health, so changes in normal sleep patterns could be a marker for a range of health problems.
But we also know that once these build-ups exist, people have difficulty getting that cleansing deep sleep. In other words, regular poor sleep could lead to a vicious cycle which makes it harder to achieve the rest the brain needs.
Sleep disruption could be a very early warning sign of declining brain health that could eventually lead to Alzheimer’s disease. Future research may use this disruption as both a screening tool and a potential target to intervene to improve sleep early in the disease development process.