“I’m so tired I don’t understand why. I sleep for eight or nine hours every night but I’m still fatigued.” I used to hear this all the time when I was working in the Sleep Clinic. We know that most people need 7 to 8 hours of sleep for every 24 hours of life to feel alert for most of the day. So sleep quantity was not the issue. After applying a whole slew of electrodes and sensors to the patient, we would watch them sleep. As the patient reported, they would sleep for a long enough period, but that eight hours of sleep would be fraught with hundreds of arousals.
An arousal is essentially a brief period of wakefulness popping into sleep. If you watch the brainwave pattern of the patient suffering from arousals, you would see slower frequency and higher amplitude activity interrupted by a burst of what normally looks like awake brainwave activity followed by higher frequency and lower amplitude activity. Sometimes you can also see brief increases in muscle tone indicating that, not only does the brain become briefly aroused, but so does the body.
The problem with arousals is that they fragment sleep, that is, they interrupt deeper sleep and bump you up into lighter sleep forcing your brain to experience more light sleep (stage one) and wakefulness  during what can feel like a good eight hours of sleep. Most of time, you don’t even know that arousals are happening because they don’t wake you up long enough for you to notice the fragmented sleep. What you will likely notice is that a normal amount of sleep, eight hours or so, or even extra long sleep like nine or ten hours, still leaves you feeling fatigued. Not only does fragmented sleep provide less restoration, but it leads to fatigue related impairments  that can impact safety and your quality of life.
Another way to look at sleep fragmentation, is to look at sleep continuity. Continuous sleep is sleep that is not broken up, that is, sleep is not fragmented. In other words, higher sleep fragmentation is the same as less sleep continuity. How do you know if sleep continuity is being reduced by arousals? Without looking at what is going on in your brain while you sleep, it is very difficult to tell. But if you seem to be able to sleep for a good eight hours straight, with maybe one brief awakening for a bathroom break or a drink of water, and you still feel fatigued, then arousals might be the culprit and it might be time for an overnight sleep study in the Clinic.
Arousals can be caused by many sleep disorders like respiratory and movement problems. But they can also be caused by poor sleep environments, medications, caffeine and stress. Stress can increase during the holiday season as we scramble to get our work done before we take a break, rush around to buy everyone gifts and pause our healthy diets and exercise routines to enjoy treats and downtime. If you are trying to figure out if you need a sleep study to see if arousals are leading to your fatigue, instead of allowing stress to increase during this holiday season, see if you can take a few days or better, a full week, to destress, improve your sleep environment, reduce caffeine intake and study the side effects of your medications. If your sleep still does not leave you feeling better, then it might be time for a sleep study.
While you are trying to reduce your arousals during sleep, keep these other pointers for better sleep in mind during this holiday season: How to Get a Good Sleep in Your Holiday Bunkhouse.
 To learn about the arousal scoring rules used by clinicians, see: Bonnet, M., Carley, D., Carskadon, M., Easton, P., Guilleminault, C., Harper, R., Hayes, B., Hirshkowitz, M., Ktonas, P., Keenan, S., Pressman, M., Roehrs, T., Smith, J., Walsh, J., Weber, S., Westbrook, P., & Jordan, B. (1992). ASDA Report, EEG Arousals: Scoring rules and examples. Sleep 15(2), 173-184.
 See, for example: Bonnet, M., & Arand, D. (2007). EEG Arousal norms by age. Journal of Clinical Sleep Medicine, 3(3), 271-274.
 For a review paper showing the strong link between fragmented sleep, lower restoration from sleep and increases in sleepiness-related daytime impairments, see: Stepanski, E. (2002). The effect of sleep fragmentation on daytime functioning. Sleep, 25(3), 268-276.