How Cranky Are You When You Wake Up?
If “rise and shine” sounds like torture to you, there’s a reason why!
While it is widely accepted that everyone’s “internal clock” (otherwise known as circadian rhythm) is different, not many studies have been conducted so far on how our internal clock affects us when we wake up.
Sleep inertia refers to the time a person needs to regain their full cognitive capacity after waking up. Some people are alert and fully functional the moment they open their eyes, while others need additional time. Many articles online suggest that the best way to feel less cranky upon waking up is to get “a good night’s sleep” and/or to exercise more. Research findings seem to disagree.
In another article, I explained about the cycles our brain goes through when we sleep, and how those cycles affect our dreams and their content. In most cases, a person who dreams in deep sleep then transitions out of this cycle while the brain’s brainwaves change to slowly wake the person up. Sleep inertia appears to be stronger in people who wake up when they are in a cycle of deep sleep, i.e. when they don’t have enough time to transition to wakefulness (source1, source2).
Another study has revealed that people who suffer from sleep-related disorders (e.g. insomnia) or mood-related disorders (e.g. Bipolar Disorder) are more prone to experience longer and stronger bouts of sleep inertia.
This is an important finding, because people in those populations were stigmatized as being “non-compliant” with behavioral treatments in clinical trials that aimed to improve their mood throughout the day.
So far, there appear to exist four major categories for sleep inertia: 1. Low, in which approximately 20% of the population fits in 2. Mild (31%) 3. Moderate (33%) 4. Severe (16%)
The category in which a person belongs to is usually specified by the degree to which they feel unable to perform cognitively right after waking up, and how much time they need to get to their baseline of full cognitive functionality (source).
People who naturally feel more alert during the evening, and those whose sleep quality is usually moderate to low (e.g. waking up during the night, having nightmares, being unable to fall asleep fast despite being tired) and sleep less than 6 hours per day, are more likely to be in the “moderate” and “severe” categories.
Moreover, while exercise right after waking up helps some people feel more alert, research has shown that alertness does not correspond to cognitive functionality. In other words, while early morning exercise helps the body feel better, your crankiness due to sleep inertia is unlikely to decrease.
While the crankiness or other behavioral manifestations of sleep inertia are usually harmless, sometimes the cognitive decline upon waking up can predispose some people to accidents or errors in judgment. This is particularly important for people who have alternating shifts, and those who work in emergency services on-call.
Therefore, knowing about one’s sleep inertia profile is important when their work hours are not consistent, and when they are in a line of work where they’re expected to be fully functional right when they wake up (source).
Finally, the way that a person behaves when they wake up is now being perceived as a trait (something a person is born with) rather than a quirk (source). This is particularly important to remember if you know someone who needs extra time when they wake up.
While some factors can be tweaked to somewhat help them (like exercise when waking up to help with alertness, or better sleep quality), eventually they will always manifest their trait baseline of sleep inertia.
How much does sleep inertia influence you? Are you ready to seize the day the very second you open your eyes?
Personally, I belong in the threshold between “low” and “mild” sleep inertia categories. However, when I go through periods of lower sleep quality I definitely notice an increase in the duration of my sleep inertia. Even though I am cognitively and behaviorally fully functional when waking up, I like to take time for myself and enjoy some moments in silence before starting my day. Those behaviors, therefore, are a personal preference rather than an influence of sleep inertia.
Special thanks to Nikolaos Skordilis whose comment in my article on Misokinesia prompted me to write about sleep inertia.