Comparing tiredness to alcohol impairment
A widely cited set of studies found that sustained wakefulness degrades performance on attention and reaction-time tasks in a way comparable to alcohol intoxication. After roughly 17 hours awake, performance on some measures resembled a blood alcohol concentration near 0.05 percent, and after about 24 hours it approached the equivalent of around 0.10 percent.
These are averages from controlled tasks, not a precise conversion for any individual, and real-world driving or work risk depends on many factors.
What sleep loss does to thinking
The earliest casualty is usually sustained attention, showing up as lapses, microsleeps, and slower responses. Working memory, judgment, and emotional regulation also suffer, while people are often poor at sensing how impaired they actually are.
Caffeine can mask sleepiness temporarily but does not restore the underlying deficit. Persistent inability to sleep or chronic daytime impairment warrants professional evaluation. This is general educational information, not medical advice.