...body clocks and Alzheimer's disease

Body clock alterations in Alzheimer’s Disease (AD) patients

The sleep pattern of AD patients is often more disrupted than that of healthy individuals of the same age, and the disruption becomes worse as the disease progresses. One of the main characteristics of sleep disruption in AD patients is fragmentation, which means that they will wake up several times during the night, instead of having one long sleep until the morning. It is usually quite hard for both patients and caregivers to cope with this situation for long periods of time, and therefore sleeping problems are a primary reason for patient institutionalisation.

Another characteristic of AD is ‘sundowning’, which is a tendency for patients to be confused and agitated in the late afternoon and evening. This could be related to mental and physical tiredness at the end of the day, however, reduced light at this time of day could also contribute to low levels of cognitive alertness. Indeed, sundowning appears to be worse during the winter months. In addition, patients who are institutionalized are generally exposed to low light levels indoors during daytime, and do not go outdoors much. This lack of a bright light signal promotes sleepiness during the day and sleep fragmentation at night. This is important, as several studies have now shown that sleep problems increase behavioural problems (i.e. agitation, aggression, hallucinations, wandering, etc.) in AD patients and the stress levels of caregivers.

How can treatment of body clock alterations help?

Studies have shown that sleep patterns can be improved in AD patients by increasing the patients’ levels of physical activity and social relations, and decreasing the time spent asleep during the day.

Since a lack of bright daytime light signal can be characteristic in AD patients, some studies have investigated the use of light as a treatment. Results show that the body clock remains responsive to light in AD patients and that those patients treated with light at specific times of day will be more awake during the day and will sleep better at night. This tends to decrease the patients’ behavioural problems and therefore improve their quality of life and that of the caregivers.

Finally, research on various neurodegenerative diseases (e.g. AD, Parkinson’s disease) and psychiatric disorders (e.g. bipolar disorder, depression) has shown that body clock –and sleep- alterations can be both a cause and effect of these diseases. As a consequence, various drugs that target the internal body clock and sleep/wake rhythms are currently being tested on patients to understand how having stable sleep patterns may prevent patients slipping back into the disorder, or even stop or slow down disease progression. Solving these problems could eventually improve the quality of life of patients and their caregivers.