When we think about sleepiness, it is first important to distinguish between being “sleepy” and being “tired”.

People often use them interchangeably, but there’s actually an important difference. Whereas sleepiness refers to being able to fall asleep at any given moment (e.g., head rolling, nodding off), being tired is a general lack of energy either physically or mentally (e.g., feeling foggy after a 3 hour exam). You can be tired without being sleepy – just like in cases of insomnia.

When it comes to being sleepy, there are several reasons why a person might feel a sense of drowsiness throughout their day. In this post, I discuss several reasons for why you might be sleepy.

1. You are sleep deprived

The first reason for why you might be sleepy is that you are sleep deprived. Whether it’s from work, taking care of kids, or social activities, you may not be getting the number of hours you need to feel rested.

It is important to also note that the number of hours each person needs can differ: some people are 8-hour sleepers, others might need more or less than that. Getting the right number of hours for you is important to reduce sleepiness.

2. Your sleep drive is high

Similar to the first reason, another reason is that your sleep drive (propensity to fall asleep at any given moment) is very high.

Sleep drive begins to build after a good night’s sleep. Based on our activities throughout the day, and how long we are awake for, our sleep drive builds up. If your schedule tends to be quite active, then it would make sense that the build-up of sleep drive is high, and sleepiness can be present.

Evidence of high sleep drive include:

  1. Falling asleep in under 10 minutes on average
  2. Evening drowsiness
  3. Spending more than 90% of the time you spend in bed sleeping.

In these cases, you likely can produce a little more sleep so it can be helpful to increase the amount of sleep opportunity you have by spending a bit more time in bed.

3. It could be natural fluctuations throughout the day

There are certain time points throughout the day where sleepiness is ‘unmasked’ because of circadian factors. These are typically around the late afternoon period (labelled the ‘post-lunch’ dip) and during the evening when sleepiness comes out. In these cases, they are a biological shift and will go away if you can push through.

4. You are bored

When there is a lack of stimulation, sleepiness can come out because our mind may begin to focus its attention on evidence of tiredness or sleepiness, such as heavy eyes or an achy body.

In this case, try to find something interesting to do!

5. There could be an underlying sleep condition

There are a few different sleep disorders that can manifest sleepiness:

Hypersomnia. In hypersomnia, you may feel excessively sleepy and/or sleep longer than usual at night. Stimulants are the first-line treatment for hypersomnia.

Sleep apnea. Sleep apnea refers to obstructions in the breathing airways that lead to mini-awakenings in the middle of the night. This can lead to sleep deprivation and thus sleepiness during the day. If you notice excessive sleepiness and loud snoring/gasps during the night, a sleep study can be helpful to determine whether sleep apnea is present.

Narcolepsy. Narcolepsy leads to suddenly falling asleep because of a deficiency in a neuropeptide (i.e., orexin) that regulates wakefulness. Stimulants are the primary treatment for narcolepsy.

Beyond sleep conditions, other medical conditions can also lead to issues with sleep, like chronic kidney disease, cancer, and anemia. Therefore, checking with your medical provider can be helpful if the sleepiness or fatigue is unexplained.

6.  Sleepiness can arise as a side effect of medication

Sleepiness can also result from a side effect of medication (e.g., pain medication, cold medication, anxiety medication, etc.). Should symptoms persist and cause issues, please check with your doctor.

Best wishes,