Definition
A disruption of the normal sleep cycle in which sleep is repeatedly interrupted, preventing a person from completing the deeper, restorative stages of sleep. Even when the total hours in bed appear adequate, the broken pattern leaves the body and mind under-rested, leading to daytime fatigue, slowed reaction time, and impaired judgment.
Plain English
Sleep that keeps getting broken up, so you wake up tired even after a full night in bed.
Context Anchor
Seen in aviation medical and fatigue discussions, especially when evaluating whether a pilot is truly rested before flying.
Derivation
Fragmentation comes from the Latin frangere, meaning to break. Sleep fragmentation is literally sleep that has been broken into pieces rather than flowing continuously through its natural stages.
Why Pilots Care
Fragmented sleep reduces alertness, slows reaction time, and raises the risk of errors or incidents even when a pilot believes they have had enough rest.
Analogy
It is like charging a phone but unplugging the charger every few minutes; the battery never reaches a full charge.
Grounding Statement
A full night of sleep can still be poor sleep if it is repeatedly interrupted.
Intuition Check
Sleep fragmentation does not simply mean not getting enough hours of sleep. It means the sleep itself is broken up, so the rest is less effective.
Example Sentence 1
After a night of sleep fragmentation caused by hotel noise, the captain elected to delay the early departure rather than fly fatigued.
Example Sentence 2
Duty-time rules are designed to limit sleep fragmentation by protecting long, uninterrupted rest periods between flights.