As a neuropsychologist, my research interests have focused on the link between sleep and cognitive health. As I have gotten older, I have personally come to appreciate the restorative power of a good night's sleep for thinking, memory, and functioning at my best.
Sleep affects our overall health, including our hormones and immune system. Neurobiological processes that occur during sleep have a profound impact on brain health, and as a result, they influence mood, energy level, and cognitive fitness. Numerous studies have shown that structural and physiological changes that occur in the brain during sleep affect capacity for new learning, as well as the strength of memories formed during the day. Sleep promotes the consolidation of experiences and ideas; it plays a pivotal role in memory, and has been shown to enhance attention, problem solving, and creativity.
Specific sleep stages are associated with different types of learning
Over the course of each night sleep unfolds in five different cycles which alternate throughout the night. These include rapid eye movement (REM) and non-REM stages. REM is the stage when dreaming occurs. This stage of sleep is associated with active eye movements and body paralysis, which assures that a sleeping person is protected from acting out the dream. During REM there is increased activity in limbic structures involved in memory and emotional regulation, whereas there is less activity in frontal brain systems involved in analytic thinking. Fragments of events and memories experienced during the day may be combined in novel and often bizarre ways during REM-based dreaming. REM plays a pivotal role in memory and other cognitive functions. Other sleep stages are also associated with memory. For instance, stage 2 (slow wave) sleep promotes motor skill learning needed for activities such as playing an instrument or keyboarding.
Changing circadian rhythms and sleep disturbances are common
When we get older, we tend to feel sleepy earlier in the evening. This may result in waking up early in the morning as our sleeping hours shift. Older people have less REM and less slow wave sleep. Less slow wave sleep may impede memory consolidation in older adults. In addition to changes in sleep cycles, older people are increasingly vulnerable to sleep disturbances that cause poor sleep and low brain oxygen such as sleep apnea, a medical condition characterized by loud snoring, breathing pauses during sleep, and daytime fatigue. Research has shown that sleep apnea increases amyloid, a protein associated with Alzheimer's disease. Poor sleep increases amyloid deposition and in turn, amyloid deposition compromises the quality of sleep. In fact, people with Alzheimer's disease are prone to sleep problems, including insomnia at night and excessive sleeping during the day.
Aging well means prioritizing sleep
We know that a good night's sleep is good for our brain, especially as we get older. But how do we do this? As a first step you should use a sleep diary to keep track of your sleep schedule for at least two weeks. This will provide objective information regarding the consistency of your sleep routine as well as the association between sleep and your level of alertness during the day.
Recommendations from sleep experts such as Dr. Suzanne Bertisch provide a road map for improving sleep hygiene. The following tips are highlighted:
Consistency matters. Train your body to sleep well by going to bed and getting up around the same time each day (even on weekends).
Only sleep when you are sleepy. Do not spend too much time awake in bed.
Pay attention to your sleep environment. Your bed should be comfortable. The room should be sufficiently dark and quiet. Some people use eye masks to block light. Some use white noise filters or ear plugs when there is noise in or near the bedroom. The temperature of your bedroom should be cool. A cool room with warm blankets is optimal for a good night's sleep.
Reserve your bed for sleep (and sex). Avoid television, reading, or work activities while in bed.
Avoid (or limit) naps. You need to be tired at bedtime. If you need a daytime nap, do this before 3 PM and for less than one hour.
Avoid stimulants (coffee, cola, chocolate, and cigarettes) for four to six hours before going to bed.
Limit alcohol intake for four to six hours before going to bed. Alcohol disrupts REM and slow wave sleep, which are important for memory.
Avoid electronic devices with LED screens for at least an hour prior to bedtime. The blue light that comes from these screens interferes with the brain's natural sleep rhythms, and may trick your brain into thinking that it is daytime.
Use rituals. Some people enjoy a hot bath one to two hours before sleep. Others use stretching or mindfulness practices in preparation for sleep.
If you do wake during the night, don't remain in bed struggling to fall back to sleep. Get up and do something that may increase sleepiness (like reading) for about 20 minutes, and then return to bed and try to initiate sleep.
Sleep is an important aspect of cognitive health, but it is not whole story. Further information regarding brain fitness can be obtained by reading our Special Health Report A Guide to Cognitive Fitness.