Sleep: Getting too much or too little?

"Government officials haven't recognised that people routinely fall asleep at night when they're doing shift work," claimed Charles Czeisler, Professor of Sleep Medicine at Harvard Medical School and Chief of Sleep Medicine at Boston’s Brigham and Women's Hospital to Randolph E. Schmid, the Associated Press’s science writer on 16 April.

“So the notion that this [sleeping on the job] has happened only a few times among the thousands of controllers is preposterous," he boomed, three days later to Boston’s Fox 25 Morning News program on 19 April.

The potential catastrophic consequences of snoozing are of course not limited to air traffic controllers, but apply across the board to many professions. Think vital services: police, state emergency services and our soldiers in Oruzgan Province in Afghanistan. And less vital: City Rail workers and Road and Traffic Authority staff.

And poor sleep hygiene is not confined to shift workers.

Many of us (including me) do get enough sleep at night but still doze off – for short periods - during the day. Every day. This is called “excessive daytime sleepiness”. Why do we do this? And for the record, just how good or how bad is our sleep the night before we exhibit EDS?

Gregory Store, Emeritus Professor of Developmental Neuropsychiatry at Oxford, in Insomnia and other Adult Sleep Problems explains the two distinct types of sleep: NREM and REM sleep.

NREM sleep makes up three quarters of adult sleep and is divided into four levels of increasing depth, called ‘stages’. Stage one is the lightest sleep and stage four is the deepest sleep. Each stage has its own sort of brain activity, as recorded by an electroencephalogram or EEG. The eyes are still, most muscles are relaxed and both breathing and heart rate are steady.

Slow EEG activity is absent in stages one and two but is present in the deep sleep typical of stages three and four. In deep sleep both eye movements and muscle activity are decreased.

NREM, characterised by being in the main devoid of dream activity contrasts with REM sleep, which involves accelerated heart rate and shallow breathing. Eyes dart rapidly in various directions, hence the name Rapid Eye Movement.  REM is where most dreaming takes place.

Our need for sleep is a function of two variables – the duration that we have been up and about and our in-built body clock, commonly called the ‘circadian body clock’, which regulates when we sleep within each 24-hour period.

High quality sleep is sound, unbroken and deep. It is restorative enough so that we can function properly the next day without the need for daytime kips. While some people make do with sleeping just a few hours, most of us need close to eight hours. To know if you get enough sleep, simply ask yourself if you tire during the day or if you ever feel drowsy enough in the day to warrant a nap?

Putting aside unusual nocturnal behavior like sleep walking and sleep terrors (grouped together as parasomnia), there are two fundamental sleep disorders – not sleeping well (called ‘insomnia’) and too much daytime sleeping (called “hypersomnia”).