Circadian Rhythm: The Relationship Between Sleep and Alzheimer's
Last updated: October 2022
As you age, your body changes. One thing that happens as you get older is your sleep patterns tend to be different. You could also have a decline in brain (cognitive) functioning, for example, difficulty remembering things. Both of these changes are perfectly normal.1
Your body's normal sleep cycle is part of your circadian rhythm (CR). Your CR describes the daily patterns of sleeping, eating, and activity that your body follows. Disruptions in CRs are linked to higher rates of Alzheimer's disease. CR disruptions caused by disturbances in sleep can be especially harmful.2,3
While cognitive decline and sleep disturbances can be expected as you age, they can also be symptoms of a more significant problem. However, there are solutions and actions you can take to improve your sleep. While they may not stop Alzheimer's, they can help slow cognitive decline and improve your quality of life.2,3
How much sleep disruption should you expect as you age?
Sleep is expected to decrease with age. Older people tend to sleep less, have more trouble falling or staying asleep (insomnia), and have more breathing issues than younger people. This is because the part of your brain that controls your CRs degenerates as you age.1,2
Disrupted CRs due to age can cause a few things to happen. You may go to bed and wake up earlier. You could also wake up more frequently at night or be sleepier during the day. Even though these can harm your health, they are also a part of aging.2
But consistent lack of sleep (sleep deprivation) and CR disruption can be early symptoms of Alzheimer's. People with neurodegeneration have CR disruption much more frequently and severely than those without.2
People with Alzheimer's can become more active during the night or less active during the day. Sometimes, their entire sleep schedules can reverse because of this. This degree of sleep and CR disruption can be a symptom of Alzheimer's and make it worse.1,2
Sleep and Alzheimer's risk
When it comes to sleep, more is usually better. People who sleep less than 5 hours per night have poorer cognitive functioning than people who sleep 7 or more hours per night. And short-term sleep deprivation has other harmful effects, including issues with:1
- Cognitive processing speed
CR disruption can also be an early symptom of Alzheimer's and may be a risk factor. This is especially true for people older than 60. People with Alzheimer's may find that their symptoms increase around the time of sunset, called "sundowning." This could be partially due to CR disruption.2
The most popular theory of Alzheimer's and sleep is that they affect each other. Alzheimer's can cause sleep disturbance as a symptom, and sleep disturbance may lead to an increase in Alzheimer's symptoms. Because of this, doctors have conclusively found that improving sleep helps to slow age-related cognitive decline.1-3
How can you improve your sleep?
There are medicines to help people with a diagnosed sleep disorder. But there are also things anyone can do to improve their sleep. These include:1,3
- Not sleeping during the day (sleep restriction)
- Bright light exposure helps to keep CRs working
- A structured exercise program that improves both sleep quality and depression in older adults
- Cognitive behavioral therapy for insomnia
- Melatonin, taken as directed by a doctor, may be helpful for sleep cycles and sleep quality
Before starting any method to fight insomnia, discuss with your doctor what is right for you. No matter your age, it is never too late to improve the quality of your sleep.
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