Not enough sleep
A single short night and accumulated sleep debt can both reduce alertness. Repeated late nights are not reliably cancelled out by determination, cold air, or loud music.
Shift work and body clock
Night work and rotating schedules ask the body to stay alert when its circadian rhythm promotes sleep. Early-morning and late-afternoon low points can also matter.
Tasks and environment
Long, repetitive, low-stimulation tasks can expose existing sleep pressure. They do not create a sleep disorder, but they can make fading more visible.
Health and medication
Sleep apnea, narcolepsy, depression, and medicines that cause drowsiness are among the issues a clinician may consider. Do not change medication without professional advice.
Sources
Written by the EyeJolt Editorial Team. Published and last reviewed 2026-07-14. Editorial policy.