You are waking up from a good night’s sleep. And you have every reason to believe that you’re ready to start a bright, new day. But no – instead you feel groggy, slow, disoriented, and drowsy. What’s going on? You are probably experiencing sleep inertia.

What is sleep inertia?

In medical terms, sleep inertia is a state of impaired cognitive and sensory-motor performance that occurs immediately after waking up. You feel disoriented and drowsy despite a long night’s sleep or perfect nap. Sleep inertia can have a temporary negative impact on situational awareness, decision making, memory and reaction time. Making it difficult to perform even simple tasks.

The effects of sleep inertia are most acute upon waking and dissipate as you transition from sleep to a complete state of wakefulness. Typically, this groggy state lasts just 15-30 minutes. In severe cases, however, prolonged sleep inertia can continue over several hours.

What causes sleep inertia?

Why does it happen? A lot is known about falling asleep. Far less is understood about the transition of sleep to wakefulness. There are several contributing factors that appear to influence the severity and duration of sleep inertia, such as sleep and circadian rhythms. Waking up during deep sleep, for example, might result in a sleep inertia experience. But studies suggest that sleep inertia can also occur in the absence of these factors. The frequency and severity of sleep inertia can also be more enhanced in people with mood disorders, such as depression, and with sleeping disorders, such as sleep apnea.

Waking up tired

You’re not alone. Sleep inertia is quite common and, in the vast majority of cases, nothing to worry about. More of an inconvenience, really. It simply takes longer for you to feel and function as if fully awake so that you can get on with your day. You ride it out. There are several options that seem to help alleviate common sleep inertia symptoms so that you can feel more awake, more quickly. Coffee or caffeinated tea might work for you, if you haven’t tried it already. Waking up with enough time to start your morning slowly and with a nice breakfast can help you ease out of inertia. If time doesn’t allow for a slow morning routine, splashing water on your face or having a shower can also help.

When to take it seriously

But when is sleep inertia more than an inconvenience and perhaps even dangerous? When there is a potential for negative real-world impacts. Since sleep inertia can severely impair performance, it is a challenge to people who have to perform safety-critical tasks or make important decisions soon after waking.

And, when you think about it, this includes everybody from truck drivers, pilots and machine operators, to those who work on-call or nap on-shift, such as first responders, doctors and nurses, as well as industry workers and military personnel. Studies show a link between sleep inertia and an increase in accidents attributed to human error within an hour of waking, while driving to work.

If you are concerned about your sleep inertia and feel that it is disrupting your life or poses a risk to you and others, be sure to speak to your healthcare provider.

Is there a sleep inertia cure?

Short naps strategically planned according to the time of day and prior sleep/wake history might help avoid sleep inertia – though more research is needed. Researchers are also exploring the effects of light, such as the sunrise, sound and body temperature on the waking process.