Waking up right is important
Waking up groggy never feels right. And how we wake up can not only affect our mood and the day’s outlook, but also our cognition and mental performance.
In some instances, grogginess after waking has the potential to be dangerous several hours later, by reducing our performance in critical decision-making (such as in health settings, emergency responses, security or while driving).
This cognitive state of reduced alertness is referred to as “sleep inertia”. It’s a growing concern as it can have serious consequences while performing high-risk tasks, including driving.
How does the brain wake up?
Transitioning from sleep to alertness does not follow an on/off switch-like system, as brain imaging techniques have revealed.
Waking relies on complex biological processes, including increased blood flow allocation to the brain. Studies show the brain regions important for alert performance (the prefrontal cortical regions) take longer to “start-up” than other areas (such as the basal ganglia) which are important for arousal. This means you can be awake, but not quite with it.
Research has also shown blood flow activity within the brain to be diminished after waking, in comparison to the pre-sleep state. Thus, alert wakefulness may in part require mechanisms that encourage a redistribution of blood flow to the brain – something certain types of sound and music can do.
Another factor that influences alertness upon waking is the stage of sleep at the time. You’re less likely to feel groggy if you wake up from a light sleep, compared to a deeper slow-wave or REM sleep.
A light sleep stage is characterised by Theta wave frequencies (as measured from the brain’s electrical activity) and can be associated with feeling drowsy. In this sleep stage, arousal from external stimuli such as an alarm can quickly draw a person out of sleep.
Conversely, deep sleep or slow-wave sleep consists of Delta wave frequencies, which are associated with unconsciousness. This is the more challenging sleep stage to fully wake up from.
Alarm effectiveness also depends on age. Young adults aged 18 to 25 need louder alarms than older people, and preteens need an even greater threshold than young adults. You may require an alarm as much as 20 decibels louder at 18 than you would at 80.
Is sound frequency and tune important?
But when it comes to choosing an alarm, what exactly is the best choice? A growing body of evidence suggests different alarm sounds can positively influence human performance after waking.
Our systematic review published in 2020 showed temporal frequencies (the pitch of the sound as measured in Hertz) around 500 Hz are better at arousing young children than 2000+ Hz varieties.
We lack research to say whether this also applies to adults, but it’s assumed the same alarm types would be beneficial.