We could all benefit from a boost in alertness, particularly when our sleep has been disrupted, or we’re feeling drowsy. Read on to find out what makes us feel sleepy in the afternoon, and how long you should nap to maximize the benefits — and minimize the downsides.
What Makes Us Feel Sleepy?
Whenever we are awake, a neurotransmitter called adenosine accumulates in our brain, as a by-product of brain cells firing. Adenosine molecules bind to receptors, slowing the brain cells down, making us feel sleepy. You can imagine this process as an hourglass that fills up during the day, increasing our drive to sleep, then flips over and empties overnight.
In contrast, our body clock, or circadian rhythm, completes a cycle once every 24 hours, and influences our drive to stay awake. Our sensations of sleepiness or alertness are the outcome of the interaction between our sleep drive and wake drive.
Our greatest urge to sleep occurs when our sleep drive approaches its maximum, and our wake drive is at its weakest. Ideally, this urge should coincide with the late evening. However, if we haven’t slept enough, we can begin the day without having completely ’emptied’ our sleep timer.
Consequently, by the time we hit mid-afternoon, the gradual drop in wake drive interacts with our higher-than-normal sleep drive and makes us crave a nap to recharge. Taking a nap is like flipping over the hourglass. As you sleep, the sand runs in the opposite direction, and sleep pressure reduces. Even if we don’t feel sleepy, this mechanism can still provide a boost in alertness.
How Long Should You Nap?
The benefits of naps are relative to their duration.
- 10-minute naps can result in immediate improvements in cognitive performance and reduced sensations of fatigue, with the benefits lasting for over two hours.
- 20-minute naps can improve physical endurance by increasing time to exhaustion and reducing perceived exertion (but only if you slept less than seven hours the night before).
- 26-minute naps may improve task performance by 34% and alertness by 50%, for several hours after the nap.
- 30-minute naps, taken after lunch, are associated with improved cognitive flexibility.
Studies have also described how naps enhance memory consolidation, improve executive functioning, and increase emotional stability.
The Downside of Napping
Unfortunately, napping also has its downsides. Naps longer than 20 to 30 minutes increase ‘sleep inertia;’ the tired feeling after you wake up. Also, taking a nap later in the day can interfere with that night’s sleep, so try to nap by the early afternoon.
READ MORE: Tired but Can’t Sleep? Here Are 5 Possible Reasons Why