Your Sleep Age™ is an overall indicator of how regenerative your sleep was last night. It corresponds to how much energy you will have throughout the day and how healthy your sleep was last night. Your Sleep Age is derived from eight main factors that have been scientifically shown to impact your health and mental performance:
1) Sleep Duration
As you get older you start to get less and less sleep. It is still unclear whether this is a symptom or a cause of neurodegeneration. However, increasing evidence is suggesting that it is causally related to various types of dimensia, diabetes, cardiovascular disease, and basically every chronic illness. For example, a typical 20-year-old will sleep for about 7.5 hours, but by the time you are 70 you are most likely to sleep only 6 hours. Some people have different sleep needs and a very small percentage of the population are known as “short sleepers,” however, your sleep duration statistic reflects the general needs of a 20-year-old to get around 7.5 hours a night.
2) Sleep Efficiency
One way to get more out of your sleep is to spend more time in bed sleeping. The percentage of time you spend in bed asleep, or sleep efficiency, is therefore one of the most important factors in improving your sleep health and overall cognitive performance. While Sonic Sleep is explicitly not a clinical device, Sleep Efficiency is how a clinician typically evaluates insomnia, where a sleep efficiency less than 85% is considered a problem. Healthy sleepers generally have a sleep efficiency of ~90% or greater. As we get older we degenerate in our ability to have consolidated sleep, or high sleep efficiency.
Did you know that its normal to periodically wake up during the night? We don’t remember most of these awakenings because most people are amnesiac to them if they occur for a minute or less. However, awakenings are considered problematic if they last for more than 20 minutes or occur frequently. While related to sleep efficiency, this measure provides insights on an aspect of sleep quality that you may not be consciously aware of.
4) Sleep Onset Latency
Another aspect of sleep efficiency is sleep onset latency, or how long it takes for you to fall asleep. If you fall asleep very quickly (i.e. < 5 minutes), this could be a sign that you are sleep depriving yourself during the day. Or in some cases this could simply mean that you are a really good sleeper. On the other end of the spectrum, if it takes you longer than 30 minutes to fall asleep, this could be a sign of eveningness insomnia. So the ideal sleep onset latency is usually around 10-20 minutes, something that becomes increasingly difficult as we age.
5) Deep Sleep Duration
Did you know that people generally get less and less deep sleep as they age? When we are in our 20s we usually spend about 1.5 hours in deep sleep, but by the time we are in our 70s its usually less than a half hour. Because of this, deep sleep is one of the best indicators of your Sleep Age. The importance of deep sleep has been demonstrated by causal evidence showing that it is related to cell recovery, memory consolidation, and next day cognitive performance
6) REM Sleep Duration
REM sleep usually remains relatively consistent with age, but this doesn’t mean that it isn’t important. REM sleep is the stage of sleep where we dream intensely and thereby encode the relevant information from the day into our personalities and long-term memory. Various substances, such as marijuana, have been shown to decrease the percentage of time in REM sleep. Even things like non-optimal temperature during sleep can shift you out of REM because you lose thermoregulation during this stage of sleep. Making sure that you spend about 20% of the time asleep in REM is thought to be ideal for optimum sleep health.
7) Brain Arousals
Did you know that even a healthy sleeper’s brain can wake up around 3-4 times per hour and you would not have any conscious awareness of this? Disruptive sounds in the environment, such as a snoring sleep partner or something as innocuous as an air conditioning turning on can wake up the brain. If you suffer from mild sleep apnea, you may have ~6-10 brain arousals / hour, with severe apnea patients having as many as 50 / hour. When your brain wakes up during these arousals it negatively impacts your sleep quality, preventing you from getting regenerative deep and REM sleep. This is more and more common as you get older and is a major cause of that brain fog that you may experience during the day.
Having a consistent bedtime is one of the easiest ways to improve your sleep health. Going to bed and waking up at the same time every day entrenches your circadian rhythm such that your body has a strong external cue for when it should be most alert and most fatigued. For example, if you were to sleep the same amount on a night where you have an irregular bedtime compared to a night with a typical bedtime you will usually get less deep sleep or REM sleep. Irregular bedtimes can also make it more likely to not get enough sleep and have more awakenings. As we get older, our circadian rhythm loses its strength, making the timing of sleep particularly important.