Sleep Inertia: Understand The Mechanism Of Sleep Inertia

Sleep Inertia

Sleep inertia was first recognized during the 1950s when American fighter pilots were allowed to sleep in their cockpits just before taking off. When the commanding officers realized that their performance was impaired, this practice was quickly terminated. Since then we have come a long way in understanding sleep inertia, the length of time from conscious awareness (awakening), to full cognitive functioning. It is particularly severe in the first ten or so minutes after awakening. In addition, studies have shown that many have a slowing of responses, loss of accuracy, and reduced* attention for up to two hours.

To better understand the mechanism behind sleep inertia, we should look to modern technology. In fact, a study published in the journal Brain in 2002 did just that. In this investigation, various areas of the brain were scanned over the first 30 minutes after awakening and showed that cerebral blood flow was most rapidly re-established in the brainstem and thalamus. This is to be expected, in that activation of these areas would result in conscious awareness. However, blood flow to the cerebral cortex, the area of higher cognitive function such as decision-making, planning, organizing, and memory, lagged by 15 to 30 minutes. Thus, we can begin to understand why many of us are foggy in the morning.

Sleep Inertia

The impact of sleep inertia on our ability to function was well demonstrated in a study published in a 2006 issue of The Journal of the American Medical Association. Researchers found that the cognitive ability of those tested immediately after awakening was poorer than when they were tested following 26 hours of sleep deprivation. The effects of sleep inertia were worse for the first ten minutes. These effects were still detectable up to two hours later. Is it any wonder that the incidence of motor vehicle accidents is highest in the early morning?

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What are some of the factors that exacerbate sleep inertia? Primarily, it is insufficient sleep. Those of us who try to get by on less than seven hours, and particularly six hours are at increased risk. Another major factor is disruption of our circadian clock. Trying to get by on very little sleep on the weekdays and then trying to make up for it by sleeping until noon on the weekend can make it worse. On Monday, when you are trying to wake up at 7:00 AM, your brain is likely to still be on the weekend time clock. You are secreting too much of the sleep hormone melatonin when its production should have dropped two hours before. As a result, you are sleepier and foggier than ever and hit the snooze button repeatedly. We in sleep medicine call this social jet lag since it so much resembles the symptoms encountered in transcontinental flight.

What can we do to at least shorten this period of brain fog? We can start by trying to ensure that we get at least seven hours of sleep. Turn off computers, cell phones, and all blue light emitting devices at least one hour before bedtime. Avoid sleep disrupting caffeine within six to eight hours of bedtime. Try to stick to a reasonable sleep-wake schedule, even on weekends and your days off. If you snore and consequently might have sleep apnea, get it checked out as well as any other sleep disrupting symptoms such as frequent urination, nocturnal acid reflux, or chronic recurring nocturnal pain.

Okay you say, “I did all that and I still can’t get going in the morning—then what”? My answer to that is help may be on the way. Some fascinating studies on DsL (dawn-simulating light) have been recently published. These devices begin to emit ever-increasing amounts of light about 30 minutes before the alarm is set to go off and for 20 minutes after. A study published in the journal Chronobiology International in 2013 titled Effects of Artificial Dawn and Morning Blue Light on Daytime Cognitive Performance, Well-being, Cortisol and Melatonin Levels, demonstrated subjects to be much more alert after DsL. They also demonstrated higher morning salivary cortisol levels in those exposed to DsL. Therefore, these dawn light simulators appear to be capable of affecting our circadian rhythms even while we are asleep and with our eyes closed. They are available at stores and online throughout the world.

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There are also devices that can be placed on your wrist, or smart phone apps placed in your bed that claim they can track your sleep and pick the optimum time to wake you. They accomplish this by tracking movement and state the best time to wake you is when you demonstrate the most movement closest to your desired wake up time. They do this either with an alarm or in the case of the wrist devices, a vibration. Unfortunately, the jury is still out on these tools. There are no well-controlled studies, such as those done for the DsL. Most of what has been published has been mixed as to effectiveness and has been written by various bloggers who have tried one or more of these devices.

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The bottom line is to understand that some sleep inertia is a normal part of the sleep-wake transition. However, inadequate sleep, poor sleep hygiene, and disruption of normal circadian rhythms can make it worse and prolong it. In most cases, if you take measures to prevent this, sleep inertia can be shortened and improved*. A good piece of advice is, regardless of how you feel, try to avoid making any serious decisions right after awakening, you are probably not at your best.

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Author

Contributor : Dr. Robert Rosenberg (Consumer Health Digest)

Robert S. Rosenberg DO, FCCP, is the medical director of the Sleep Disorders Center of Prescott Valley, Arizona and sleep medicine consultant for Mountain Heart Health Services in Flagstaff, Arizona. He is the author of "Sleep Soundly Every Night; Feel Fantastic Every Day" (Demos Health) and is also a contributing sleep expert blogger at EverydayHealth.com.

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