I recently finished reading "Why We Sleep" which is sobering read including the long term health hazards of repeated sleep disruption - I highly recommend it to anyone involved in safety critical industries such as airline flying.
The author states (backed up by evidence) that we are now living in a sleep deprived society for many different reasons. In particular the sleep which is missed is typically the last 2 hours of a 7/8 hour sleep where individuals have to wake up to an alarm clock (for example for early work duties). This last two hours is in fact
the most important part of a night's sleep. During sleep we go through several cycles of non REM and REM sleep which are all essential especially from a health standpoint. The length of REM sleep increases with each cycle so if you miss the last 2 hours you're missing out in a proportionately higher way.
The author also mentions the difficulty he has when talking to CEOs etc of companies and convincing them (with proof) that sleep deprived employees are less likely to be productive etc.
Another factor worth mentioning is that before the requirement for flight deck doors to be locked it was quite common for pilots to get out the seat to stretch their legs every now and again and even walk down the back to talk to the passengers. Now they are virtually imprisoned on the flight deck.
Also consider this from a pure financial point of view. In the early 1980s when flying for a leading charter airline we worked out that if we lost one pilot (whether due failed medical or moving to another employer) it cost the company around £20,000 to replace him/her with another pilot in terms of having to have adequate training staff and infrastructure etc. I wonder in today's money what the equivalent amount would be although I am aware that the odd loco makes a "profit" on their training "machine".
Finally, slightly off thread but interesting to note that the circadian rhythm of adolescents is about 2/3 hours different from adults. So when you have difficulty getting your teenager out of bed in the morning it's simply because for various reasons nature has programmed them for a different circadian rhythm. Many mental health conditions such as schizophrenia start in adolescence and the author suggests this is caused by insufficient sleep and that school times should be adjusted for this age group (e.g. start at 1000, finish at 1900) for this reason. School start times have become progressively earlier with many children having to wake at 0600 or even earlier to catch the school bus for early school start times and/or "breakfast clubs". I'd just finished reading this section of the book and switched the news on to hear about the shooting at a school in Florida which got me thinking! You have to read the book to read some compelling evidence on how mental health issues can be tracked back to repeated sleep disruption. There are also ramifications for sleep deprived aircrew and their long term mental health, I believe.