"Falling Asleep in the Car? Your Body Might Be Warning You About Something Serious"
- caulocare
- Jun 1
- 4 min read
By Dr. Caulo Phumlarp, Doctor of Acupuncture and Chinese Medicine
Caulo Care, New York, June 1, 2025
A Warning Sign from Your Lungs, Spleen, or a Silent Sleep Disorder
Introduction
Many people have unintentionally dozed off during a car ride—whether as a silent passenger or, alarmingly, as the driver who must open windows or blast music to stay awake. But falling asleep in the car isn’t merely a sign of fatigue. Rather, it may reflect a complex interplay of biological, psychological, and energetic systems within the body.
This article will explore the causes of drowsiness while riding in a car through three distinct lenses:
Conventional Western medicine
Traditional Chinese Medicine (TCM)
Psychology
It will also connect these perspectives to obstructive sleep apnea (OSA)—a dangerous and often overlooked condition that can silently disturb sleep and affect daytime alertness. A brief historical journey into the discovery of sleep apnea will further contextualize the significance of this silent yet impactful disorder.
🔬 Western Medicine: The Body Enters “Autopilot Rest Mode”
There are several biological explanations for why one might become sleepy in a moving car:
1. Activation of the Parasympathetic Nervous System
When you are not actively driving, your body transitions into the rest-and-digest mode, managed by the parasympathetic nervous system. The engine’s hum and the car’s gentle vibration mimic “vibrational therapy,” calming the brain and downregulating the sympathetic nervous system—the system responsible for alertness and stress response.
2. Sleep Debt and Homeostatic Sleep Drive
Human sleep is regulated by homeostatic pressure—an internal clock that accumulates “sleep debt” the longer we stay awake. If you’re sleep-deprived, even briefly sitting still in a low-stimulation environment (like a car) gives your brain an opportunity to repay that debt by entering a sleep state.
3. Rhythmic Sensory Input
The repetitive low-frequency sound of the engine and the car’s motion impact the thalamus, the brain’s sensory relay center. This stimulation suppresses activity in the cerebral cortex, reducing sensory awareness, similar to how white noise soothes infants to sleep.
4. Post-Meal Blood Flow Shift
If you sit in a car after a meal, more blood is redirected to your digestive system. This reduces cerebral blood flow, resulting in mild mental fog and drowsiness.
5. Reduced Oxygen Levels in a Closed Car
Poor air circulation in a sealed vehicle can lead to a mildly reduced oxygen concentration. Lower oxygen availability impairs brain function, contributing to sluggishness and sleepiness.
6. Neurochemical Mechanisms
Adenosine, a neuromodulator that builds up the longer we stay awake, signals the brain to sleep. In relaxed settings—like sitting in a car—there are no opposing stimuli to counteract adenosine’s sedating effect.
🧠 Psychology: The Brain Escapes Boredom by Sleeping
From a psychological standpoint:
Sensory monotony, such as long stretches of identical scenery or repetitive road noise, reduces cortical engagement, causing the brain to shift into a passive, resting state.
Unresolved sleep debt makes the brain opportunistic, seizing any moment of quiet to slip into microsleep or full dozing, even if it’s unintentional.
🌬️ Traditional Chinese Medicine: The Spleen and Lung Connection
According to TCM:
The Lung (Fei 肺) governs the skin and body hair, and is responsible for distributing Wei Qi (衛氣)—the body’s defensive energy. If the lungs are weak, external pathogens such as wind, dampness, and cold can penetrate the surface more easily, weakening alertness.
The Spleen (Pi 脾) is responsible for digestion and Qi production. If the Spleen is deficient, Qi fails to ascend to the brain, resulting in mental fog and fatigue.
Sitting still in a car slows Qi circulation. Combined with rhythmic motion, this creates an effect similar to “soothing massage,” encouraging sleep.
🛏️ Sleep Apnea: The Hidden Force Behind Daytime Drowsiness
One condition directly associated with unexplained daytime sleepiness is obstructive
sleep apnea (OSA).
In OSA, the airway collapses intermittently during sleep, causing breathing to stop momentarily, often dozens of times per hour. These interruptions prevent deep sleep. The brain repeatedly “micro-awakens” to restore breathing, without the person ever being aware.
As a result, patients often:
Sleep 7–8 hours yet feel exhausted
Fall asleep easily while riding in a car
Experience morning headaches, poor concentration, or irritability
🧭 A Historical Glimpse: The Discovery of Obstructive Sleep Apnea
Though similar conditions were described in earlier eras, the first modern medical description of OSA is credited to Dr. Sidney Burwell and colleagues. Their foundational work is acknowledged in:
The Centennial Book of the American Thoracic Society (2005)
Burwell’s observations identified the pattern of loud snoring, disrupted sleep, and profound daytime fatigue as a specific syndrome rather than vague symptoms.
📜 Earlier Accounts
Before Burwell’s work, similar symptoms were observed but not clinically defined:
Russell (1866) described chronic excessive sleepiness
Broadbent (1877) reported cases of periodic breathlessness during sleep
Morison & Caton (1889) studied the brain’s circulation during abnormal sleep behavior
Still, it was Burwell’s systematic study that laid the foundation for what we now call obstructive sleep apnea.
✅ Conclusion: Sleepiness in the Car Shouldn’t Be Ignored
Falling asleep in the car might seem harmless, but frequent or sudden drowsiness, especially when unrelated to poor sleep, can be a warning sign.
If you:
Doze off easily during short car rides
Snore loudly at night
Wake up tired despite adequate sleep
…it’s time to consult a sleep specialist or undergo a sleep study. What appears to be simple tiredness might be the body’s cry for help, whether from a Spleen Qi imbalance, oxygen deficiency, or a dangerous sleep disorder like OSA.
📖 References
The Centennial Book of the American Thoracic Society. American Thoracic Society. 2005.
Russell JB. (1866). “On excessive sleepiness in men.”
Broadbent WH. (1877). “Remarks on certain cases of periodic breathlessness.”
Morison A., & Caton R. (1889). “Observations on the cerebral circulation during sleep.”
This information is only educational and should not be construed as medical advice.
Everything must be balanced, and the suggestions may not apply to you.
A specialist doctor should be consulted for any medical advice or diagnosis.
BOOK AN APPOINTMENT NOW!
Acupuncture near me at Forest Hill, NY
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Dr. Phumlarp Caulo LA,c, MAc. OM, DAHM
Doctor of Acupuncture/Chinese Medicine
Caulo Care Acupuncture
🔖 By appointment only
☎️+1 (929) 269-4549
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