Increasingly, we are hearing reports of people falling asleep while driving with terrible consequences as they hit unsuspecting people and even endanger their own lives. The latest case is of a Gurugram-based civil engineer, who was arrested for ramming into two men, including a law student, after he fell asleep while behind the wheel.
Why your brain craves sleep
Falling asleep at the wheel is a dangerous consequence of a fatigued or sleep-deprived brain. “When we are sleep-deprived, the brain experiences ‘microsleeps’ — brief, involuntary episodes of sleep that can last a few seconds. During these moments, a driver can lose awareness and control, even with eyes open. The brain’s prefrontal cortex, responsible for attention, decision-making, and alertness, becomes less active, impairing our ability to stay focused or respond quickly to road conditions,” says Dr Vinit Suri, senior consultant, Neurology, Indraprastha Apollo Hospitals, Delhi.
The brain’s sleep-wake cycle, governed by the circadian rhythm, also plays a critical role. Driving during low circadian alertness periods — such as late at night or early morning — increases the risk of drowsiness. “Neurochemicals like adenosine, which build up during waking hours, signal sleep pressure to the brain; without rest, this pressure continues to mount, further weakening alertness. The reticular activating system (RAS), which helps keep us awake, starts to underperform when fatigued, making it harder to stay aroused. At the same time, the thalamus — a relay centre for sensory and motor signals — becomes less responsive, reducing awareness of surroundings,” explains Dr Suri.
Drowsiness also suppresses activity in the brain’s region responsible for vigilance and perception. “Furthermore, a monotonous driving environment with little stimulation accelerates the decline in brain alertness. In essence, when the brain is too tired, its ability to prioritize staying awake over sleep fails, making it override even conscious efforts to stay alert,” says Dr Suri.
A night’s lack of sleep of less than six hours has been found to impair vigilance, reduce reaction time and decrease decision-making abilities in a similar way to alcohol consumption, according to Dr Aditya Gupta, Director, Neurosurgery & Cyberknife, Artemis Hospital, Gurugram.
What are warning signs?
Warning signs like frequent yawning, heavy eyelids, or drifting lanes should never be ignored. “To prevent such cognitive shutdowns while driving, adequate sleep, regular breaks and avoiding driving during drowsy hours are essential. Fatigue behind the wheel is not a sign of weakness — it is a neurological warning that must be taken seriously,” he says.
Patients with obstructive sleep apnoea may also have excessive daytime drowsiness, resulting in naps while driving and hence a history of heavy snoring should be taken, and if required, a sleep study too.
What should you watch out for?
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“We also caution against too much dependence on stimulants such as coffee or energy drinks. These can give a transient boost to alertness but cannot substitute for the brain’s requirement for sleep,” says Dr Gupta. When their action wears off, sleep can hit one suddenly and uncontrollably.
To avoid drowsy driving, he suggests getting 7–8 hours of sleep prior to long driving, resting breaks every two hours and not driving during the circadian low points. “In the event of extreme exhaustion, the only solution is to stop and take a rest,” he adds.
