Episode 46: Sleep, Aging, and Cognition with guest Dr. Ashley Curtis
About Dr. Ashley Curtis
Dr. Ashley Curtis’ interest in sleep, cognition and aging started when she worked as a sleep technician in Toronto, Canada. She was one of those people that put the electrodes on people's heads and watched their brain waves as they slept. She also did some work in pharmacological trials, where she looked at the effects of different sleep medications on sleep and people with insomnia. Then she went to grad school and started studying more about not just sleep, but also cognition.
Dr. Curtis received her doctoral degree in Psychology (with a specialization in Brain, Behaviour and Cognitive Science) from York University in Toronto, Canada. She completed several Postdoctoral Fellowships, including one in the Mizzou Sleep Research Lab in the Department of Psychiatry at the University of Missouri. Dr. Curtis is currently an Assistant Professor in the Departments of Psychiatry and Psychological Sciences at the University of Missouri and the Director/Principal Investigator of the Cognition, Aging, Sleep, and Health (CASH) Lab. Dr. Curtis’ research focuses on the bidirectional relationship between sleep and cognition in healthy and pathological aging populations.
Sleep & Cognition
Everybody knows that sleep is important. You know that after a night of poor sleep, you’re not at your best. You're foggy and fatigued throughout the day. Poor sleep has an impact on your daily life.
There's also been a lot of research showing that sleep, poor sleep, is associated with worse memory. We've known this ever since they were cutting into the brain to the brains of rats. Getting a good night's sleep is needed for your memory to function properly. Sleep is also important for other cognitive abilities. If you sleep too little or too much, this can impair your mental functioning.
The importance of sleep is a particularly important conversation to have with older adults since this population shows an increased prevalence of insomnia. In older adults, about 50% experience insomnia symptoms. So, there is an increase in the prevalence of sleep disturbance among this population. Older adults also have a lot more problems with their health and more medical comorbidities. Recent work suggests that having insomnia can increase your risk of developing further cognitive decline, specifically Alzheimer's disease. We need to pay more attention to the association between sleep and cognitive performance.
There's a bi-directional relationship between sleep and cognition, but the scientific community doesn’t yet have a firm grasp on the exact mechanism that's underlying this relationship. There's been a lot of hypotheses out there and some interesting research findings. One explanation is that when you have a night of poor sleep, you're not getting the proper amount of deep sleep. You're getting more of what is called lightwave sleep. Since you're not getting that deep sleep, you're not getting this consolidation of your daily memories, which impairs your cognitive performance.
Other theories talk about the neural mechanisms that are happening at night. Specifically, when you are asleep, you are removing some of the neural aggregations that are associated with dementia. Given this, sleep may be important for getting rid of those plaques and tangles, which are associated with Alzheimer's disease. Although there's a lot of research out there, this area of research is really in its infancy. The scientific community doesn’t really know the exact mechanism that links sleep with cognition. Over the next 20 years, we're going to get a lot more answers.
Measuring Sleep
Subjective measures of sleep:
Ask people how they're sleeping
Sleep diary (e.g., how long did it take you to fall asleep? How often were you up at night? Can you rate the quality of your sleep? How fragmented was your sleep?)
Polysomnography – measures brain waves, blood oxygen level, heart rate and breathing, as well as eye and leg movements during sleep. Electrodes are put on your head, chest and legs, and a technician will look at how your brain is behaving during sleep. The electrical signals provide a sense of the patterns of your sleep architecture. It reveals how much deep sleep you're getting, how much light sleeper getting, how much REM sleep you're getting.
What is Sleep Architecture?
Your sleep architecture is something that changes across the lifespan.
Stages of sleep
REM sleep: rapid eye movement sleep. It's the stage of sleep where we are dreaming.
Stage 1 and 2: Lighter stage of sleep.
Stage 3 and 4: Deeper aspects of sleep. This stage is believed to be where more of the memory consolidation is taking place.
So, it's really important to get that deep sleep. If you don't get that deep sleep, you're more likely to wake up because you're in these latter stages of sleep. It can also have implications for next day cognitive functioning.
Typically, your whole sleep cycle lasts about 90 minutes. As people age, they spend more time in the lighter stages of sleep and less time in these slow-wave (deep) sleep and REM sleep. Not getting enough deep sleep is one potential reason why older adults experience a higher prevalence of sleep disturbance.
Normal vs. Abnormal Sleeping Patterns
Insomnia is defined as chronic sleep disturbance. So, over three months, for example, and at least three nights a week, you are having problems falling asleep (unable to fall asleep in 30 minutes or more), and staying asleep. Insomnia is if you experience these sleep disturbances chronically for three months, and you also experience daytime dysfunction associated with a lack of sleep (e.g., cognitively sluggish, irritable mood, etc.).
You can also look at your sleep architecture, which is typically around 90 minutes long (to have the whole cycle.)
Individuals spend more time in slow-wave sleep when they're younger and less time when they get older. If you experience less time in slow-wave and REM sleep, this could be indicative of having an abnormal sleep pattern.
There's also another way that you can look at sleep - you can look at people's circadian rhythms. Your circadian rhythm is how their body functions throughout the day, and it metabolizes things and how sleepy they feel in the morning versus the night. So that's another way that we can then we can look at sleep as well.
How your everyday actions impact your circadian rhythm
You have to actually use our body and move around (be active) to increase your sleep drive throughout the day. Oftentimes people don't consider that when they are not sleeping as much at night. The fact is that they might not be creating enough of a sleep drive for themselves because they're not active enough.
How much light you're getting
Don’t take naps – because they can disrupt your normal circadian rhythm.
As people age, there is a shift in their circadian rhythms. So, they will want to go to bed earlier and wake up earlier because. This naturally occurring shift in circadian rhythm is important to understand because people might not know this shift in sleep patterns is a normal part of aging. As such, there is no reason to try to compensate for it, because you would just be interfering with a normal aging process.
Chronic Pain, Sleep and Cognition
Chronic pain is it is more prevalent in older adults and than in younger adults. Dr. Curtis conducted some research to explore the role of a history of chronic pain versus this more acute rating of pain. Specifically, she examined whether people with a history of chronic pain differed from people without a history of chronic pain in the relationship between sleep and different types of cognitive functioning. She found that they did differ.
Research findings
If you had chronic pain and you were an older adult, measures of how fragmented your sleep was predicted cognitive performance. If you didn't have a history of chronic pain, Dr. Curtis didn't see this associated.
People with a history of chronic pain, their actual day-to-day pain ratings were not associated with cognitive performance. In contrast, people without a history of chronic pain, their daily ratings of pain were associated with their cognitive performance.
Medical Comorbidities, Sleep and Cognition
Cardiac patients, for example, people who have cardiac disease, often have heart implants. It's called implantable cardioverter-defibrillator (ICD) and is often associated with pain and anxiety. Individuals with these devices also have a higher prevalence of insomnia relative to people without them. Dr. Curtis was interested in looking at how sleep impacted cognition in this population.
Research findings
Sleep did impact cognition in individuals with an ICD.
Individuals with ICDs who slept longer showed better cognitive performance.
A follow-up study found that it wasn't just how long they were sleeping - if participants had less fragmented sleep, this was also associated with cognitive performance.
Of cardiac patients with these devices (ICDs), only those that had higher pain ratings showed a relationship between sleep fragmentation and cognition.
Mental Health, Sleep and Cognition
Typically, people who are more anxious have a harder time falling asleep because they're ruminating. You also can’t sleep properly if hyper-aroused physically. As such, being anxious can make it more difficult for someone to calm down and go to sleep. Anxiety is also associated with waking up more times throughout the night. But, if you have a poor sleep, you can be more anxious the next day. So it's kind of a cyclical pattern. Anxiety is a target for a lot of behavioural treatments for insomnia. Cognitive-behavioural therapy for insomnia targets anxiety and arousal. You know that if you have a poor night's sleep, it's going to impact your cognition the next day. It's important, too, to manage that anxiety.
Healthy Aging & Sleep
Sleep impacts almost everything that you do. In this way, sleep is associated with all these different aspects of functioning - not just cognition, but also mood, activities of daily living, physical activity, etc. All these pieces together mean that sleep will ultimately impact your quality of life. So, if you're not sleeping well, this will be associated with a reduced quality of life. The scientific literature also shows us that quality of life is associated with worse cognitive function, and it can result in further functional decline as well. So, you must try to mitigate that. One of the first steps to target is sleep. If older adults are experiencing quality sleep, it will help them better live their day-to-day lives, and hopefully help them live independently for longer – the ultimate goal of any aging researcher.
Strategies for Improving Sleep Quality
First off, speak to your doctor, if your sleep quality is something that's concerning you. There are a lot of behavioural treatments (e.g., cognitive behavioural therapy or just behavioural therapy) for insomnia that have been shown to be very effective. If people are taking prescription medications and they're having problems with that, they should speak with their doctor and potentially ask for other avenues to explore – e.g., behavioural treatments for their sleep.
In cognitive-behavioural therapy, it's not just improving your behaviour it is also improving your sleep hygiene.
Take your phone out of the bedroom
Don’t watch TV when you’re trying to go to bed.
Only lie in bed, awake for a certain amount of time. If you're not falling asleep, get out of bed and do something that's not arousing until you're sleepy again and then go back to sleep. You want your bedroom to be associated with sleep and falling asleep. You want to create strong connections between the bed and sleep.
Do not nap during the day, as you want to create that sleep drive and that need for sleep so that you fall asleep more quickly.
Pay attention to medications that you're on for, for particular side effects.
There is also dealing with the cognition associated with insomnia. A lot of people who have insomnia symptoms have anxiety surrounding it. Ask yourself:
Why do I feel this way? Try to come up with alternative cognitive thoughts to reduce the anxiety around your insomnia symptoms.
It's a holistic approach (targeting your behaviour and cognition) to help you sleep better and to teach you what you need to know to sustain that improvement.
Medication as a sleep aid is often more of a temporary fix, as you're not getting at the underlying root cause of your sleep issue and address that.
The bottom line is that your body and your physiology want to sleep. So, you just need to support it in trying to achieve what it naturally wants to do. You just need to get rid of some of the roadblocks and barriers that are getting in the way.
Conclusion
To learn more about the work that Dr. Ashley Curtis is doing, you can visit her “Cognition, Aging, Sleep and Health Lab” website by CLICKING HERE.