Why am I not sleepy at bedtime, even though I’m exhausted?

In the world of sleep science, “tired” and “sleepy” are very different things. Although you might feel drained at the end of the day, you won’t fall asleep until that overpowering urge to drop off comes over you.

“Tiredness” is what you experience when you feel physically and mentally fatigued, whereas “sleepiness” is the irresistible desire to fall asleep. This sleep pressure (also called sleep drive or sleep urge) should increase steadily through the evening, but a range of factors can interfere. If you are always busy, you may be too awash with the stress hormones adrenaline and cortisol for the sleepiness hormone, adenosine, to increase your biological sleep pressure. Stimulants such as caffeine and certain medications can also prevent sleep pressure from building.

At the end of a busy day, we need to give ourselves adequate time to wind down, allow sleep pressure to build naturally, and make sure we can recognize the physical signs of our sleepiness.

PAST YOUR BEDTIME

Nodding off and a heaviness in your limbs are sure signs that your body is ready to fall asleep. If you don’t experience these at your regular bedtime, try staying up until you are really struggling to stay awake. Doing this will let the sleep pressure build, allowing you to rediscover what it’s like to feel sleepy.

Building the pressure

Ideally, your urge to sleep would follow a daily pattern like this, with sleep pressure at its lowest when you wake refreshed in the morning, then building steadily to a peak in the late evening, when you fall asleep.

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