Microarousals Explain Why You Sleep but Do Not Rest A microarousal is a shift from deeper sleep to lighter sleep that lasts 3-15 seconds. Your brain waves change from the slow, synchronized patterns of deep or REM sleep to the faster patterns of wakefulness. Your heart rate spikes briefly. Your muscles may twitch. You do not wake up fully, and you typically have no memory of the event. But each microarousal interrupts the restorative process your brain was performing (Ouellet et al., 2015). Everyone experiences microarousals. A normal arousal index (the number per hour of sleep) is 5-15 in healthy adults. Your brain checks in with the environment periodically during sleep as a survival mechanism. The problem after concussion is that this number increases dramatically. An arousal index of 17-25+ is common in post-concussion patients. That means your brain is interrupting its own repair process every 2-4 minutes throughout the night. This is why you sleep 9-10 hours and wake feeling unrested. The total sleep time looks adequate. The sleep efficiency is not. Your brain never sustains the deep, slow-wave sleep long enough to complete the restorative processes that clear metabolic waste, consolidate memory, regulate hormones, and repair neural tissue. You are getting quantity without quality. How Concussion Increases Microarousal Frequency Autonomic hyperarousal lowers the arousal threshold. After concussion, the sympathetic nervous system stays activated even during sleep. Your nervous system's threat detection threshold drops. Stimuli that would not wake a healthy brain (a partner shifting, distant traffic, room temperature changes) are enough to trigger a microarousal in a hyperaroused brain. The nervous system is on guard duty when it should be in recovery mode (Wickwire et al., 2018). Neuroinflammation disrupts sleep-regulating circuits. The brain regions that control sleep-wake transitions (ventrolateral preoptic area, hypothalamus, brainstem reticular formation) are affected by the neuroinflammatory cascade of concussion. Inflammatory cytokines alter the function of sleep-promoting neurons, making sleep transitions unstable. Your brain oscillates between sleep states instead of maintaining them. Damaged proprioception from cervical injury triggers arousal. The whiplash component of concussion damages cervical proprioceptors. During sleep, head position changes on the pillow send abnormal proprioceptive signals to the brainstem. These signals are interpreted as a threat (the brain cannot confirm its position in space), triggering a microarousal to check the environment. Every time you shift your head on the pillow, your damaged proprioceptive system sounds a false alarm. Pain breaks the sleep cycle. Headache, neck pain, and muscle tension from post-concussion guarding produce nociceptive (pain) signals that trigger arousal even when the pain is not severe enough to wake you consciously. Subconscious pain processing pulls your brain out of deep sleep repeatedly. Thermoregulatory instability. Autonomic dysfunction disrupts temperature regulation during sleep. Brief temperature spikes trigger microarousals as the body attempts to correct the thermal imbalance. This is why night sweats and feeling too hot are associated with fragmented sleep after concussion. Measuring Your Microarousals Polysomnography (PSG) is the gold standard. An overnight sleep study measures brain waves (EEG), eye movements, muscle activity, heart rate, breathing, and blood oxygen. The arousal index is calculated from the EEG data: the number of times per hour your brain waves shift from sleep to wakefulness patterns. A post-concussion patient with an arousal index of 17-25 is having their restorative sleep interrupted 100-150 times per night. Consumer wearables provide approximations. Devices like the Oura Ring, Whoop, and Apple Watch track heart rate variability (HRV) and movement during sleep. They report "restfulness" scores and "wake" episodes that approximate microarousal patterns. These are not as accurate as PSG but provide useful trend data. If your wearable shows consistently low deep sleep percentages and high "restlessness" scores, microarousals are likely elevated. When to request a sleep study: If you sleep 8+ hours and wake exhausted consistently, if your concussion specialist cannot explain your fatigue, if you have night sweats or heart pounding during sleep, or if sleep medications are not improving your rest quality. The sleep study provides objective data that guides treatment decisions. Pre-Sleep Protocol to Reduce Microarousals Reducing microarousals requires lowering the autonomic arousal threshold before and during sleep. This pre-sleep routine performed 30-60 minutes before bed shifts the nervous system toward parasympathetic dominance. JME 1 Slow cervical rotation with extended exhale breathing. 10 repetitions at 3-4 seconds per direction. Exhale during the rotation (6-8 seconds), inhale during the return (4 seconds). This combination provides mechanical vagal stimulation through cervical movement and physiological vagal activation through extended exhale. The goal is reducing the sympathetic tone that keeps the arousal threshold low. JME 14 Chin tucks held for 10 seconds each, 8-10 repetitions. The deep cervical flexors provide the brain with accurate head-position information. Restoring this proprioceptive accuracy before sleep reduces the false alarms that damaged proprioceptors generate when head position changes on the pillow during the night. JME 3 Lateral cervical flexion releases the upper trapezius and scalene tension accumulated throughout the day. Entering sleep with reduced cervical muscle tension lowers the pain-mediated arousal signals that trigger microarousals. Spend 10-15 seconds per side, 5 repetitions. JME 5 Gentle cervical extension mobilizes the suboccipital muscles. Suboccipital tension contributes to the base-of-skull headache that worsens in supine positions and triggers microarousals. Releasing this tension before lying down removes a key arousal trigger. Start your 14-day free trial for bedtime nervous system routines that improve sleep quality. Thoracic and Breathing Preparation for Sleep JME 153 Thoracic extension with 10 diaphragmatic breaths. Open the chest fully, breathe into the belly, exhale slowly. This positions your respiratory system for the deep, slow breathing of parasympathetic sleep. Restricted thoracic mobility limits breath depth, which reduces vagal tone during sleep and maintains the elevated sympathetic state that triggers microarousals. JME 150 Gentle thoracic rotation mobilizes the ribcage and intercostal muscles. Rib mobility affects breathing mechanics during sleep. Restricted ribs produce compensatory breathing patterns that are less efficient at maintaining parasympathetic tone through the night. JME 42 Shoulder mobility before bed releases the shoulder elevation pattern that many concussion patients carry into sleep. Lying down with elevated, tense shoulders increases cervical compression and reduces breathing efficiency. Consciously releasing shoulders before bed improves both the cervical and respiratory components of sleep quality. JME 6 Cervical flexion gently stretches the posterior cervical muscles as the final exercise before lying down. This releases the extensor muscles that will be in a shortened position during supine sleep. Starting with these muscles at their resting length reduces the nocturnal guarding that triggers microarousals. Improve your sleep quality with simplmobility's pre-sleep programming. Environmental Strategies to Reduce Microarousals Temperature: 65-67°F (18-19°C). A cool room reduces the thermoregulatory microarousals caused by autonomic dysfunction. Your core temperature needs to drop 2-3 degrees for sleep onset and maintenance. A warm room prevents this drop and triggers arousal responses as the body attempts to cool itself. Sound masking. White noise or brown noise at consistent volume masks the environmental sounds that trigger microarousals in a hyperaroused nervous system. The key is consistency: variable noise (traffic, a partner) triggers arousal. Steady noise does not. A fan or dedicated white noise machine works better than a phone app that might produce notifications. Pillow optimization. Your pillow determines cervical alignment during sleep. A pillow that pushes your head into flexion or allows extension stresses cervical structures, generating proprioceptive and pain signals that trigger microarousals. Your head should be in neutral alignment with your spine. Side sleepers typically need a thicker pillow. Back sleepers need a thinner one. Stomach sleeping stresses the cervical spine and should be avoided during concussion recovery. Light elimination. Any light reaching the retina suppresses melatonin and raises arousal threshold. Use blackout curtains. Cover LED standby lights on devices. If a nightlight is needed for orientation during middle-of-night waking, use red or amber light, which has minimal melatonin-suppressive effect. Is an arousal index of 17-19 concerning after concussion? Yes, 17-19 per hour is above normal (5-15) and explains chronic fatigue despite adequate sleep duration. At 17 microarousals per hour, your brain exits restorative sleep approximately every 3.5 minutes. Deep sleep stages require sustained periods of 20-40 minutes to complete their restorative functions. An arousal index this high prevents the brain from completing a single full cycle of restorative sleep. The good news: this is treatable through autonomic regulation, sleep environment optimization, and sometimes medication. Do microarousals show up on a smartwatch? Consumer wearables detect some microarousals but miss many. They identify arousals associated with significant movement or heart rate changes but miss the subtler EEG-only arousals that a sleep study captures. Wearable data showing low deep sleep percentages (under 15% of total sleep), high "restlessness" scores, and frequent brief "wake" episodes correlates with elevated microarousal indices. Use wearable data as a screening tool and trend tracker, not as a diagnostic replacement for polysomnography. Will microarousals resolve as my concussion heals? For most mild concussions, microarousal frequency decreases as autonomic function normalizes over 4-12 weeks. Active intervention (pre-sleep mobility, breathing protocols, sleep environment optimization) accelerates this timeline compared to passive waiting. For patients with persistent post-concussion syndrome, elevated microarousals can persist for months and may require medication (low-dose clonidine, prazosin, or gabapentin) alongside the behavioral interventions. Track your sleep quality over weeks to confirm improvement. References Ouellet, M. C., et al. (2015). Sleep disturbances following traumatic brain injury. Current Treatment Options in Neurology, 17(10), 46. PubMed Wickwire, E. M., et al. (2018). Sleep, sleep disorders, and mild traumatic brain injury. Neurotherapeutics, 15(1), 22-33. PubMed