Unstable adaptation

It is possible that the adapted state is unstable or gets destabilized for a sleeper. Some events, injuries or substances can throw off the sleeper from being adapted in most cases. There are a few types of sleep destabilization or generally unstable adapted state, which are described below.

Low total sleep time

It is usually very difficult to adapt to schedules with a low total sleep time, since much more sleep compression should occur, leaving significantly much less light sleep. This makes the sleep schedule much less flexible and generally unstable, because any event or substance, which temporarily increases sleep needed, can easily compromise adapted state. This is likely the main reason why long term polyphasic sleepers more often are those, who stay on a schedule, which reduce little-to-no sleep, while most nap-only adaptations.

Also, schedules, which reduce much sleep, require much denser blocks of sleep during the day because of the wake time reduction, so shorter wake gaps are possible, which makes such schedules inconvenient for daily life and thus unstable long term.

Increased sleep needs

Sleep needs can be increased temporarily, usually as an effect of needed physical recovery. Such cases include increased physical activity, some substances, such as marijuana