Sleep till the end of your daze...

... it will help your lectures and cut your mortality risk, says Kevin Fong

If you deprive rats of sleep for long enough, they die. They just waste away. Nobody is sure why, but it is a safe conclusion that lack of sleep is bad for you. This is often on my mind as I stick my head into the stream of water from the shower in an attempt to wake myself up while desperately trying to remember whether or not I have already washed my hair.

Clinical lecturers sneak in their lecturing commitments when and where they can. Sometimes this means delivering your piece after you've been up all night and are more than ready for bed. Of course, it's wrong to go to the podium in a state of extreme exhaustion, and if you've had a bad night for whatever reason, it would almost certainly be better for you and for the students to postpone that day's lecture and reschedule it for another time.

But however rough you feel, the sight of those happy, smiling, expectant faces (as well as the thought of the tirade of abuse that you'll come in for when the feedback forms arrive at the end of the course) are usually incentive enough to make you soldier on.

And, of course, you don't want to feel like a wimp. After all, many famous tough people throughout history have been known to get by on very little sleep. The Iron Lady apparently squeaked by on an average of five hours a night, and John F. Kennedy was known to be king of the power nap.

But try as you might, you just can't kid your body. Soon enough, all of that lost slumber catches up and leaves you in a kind of twilight existence in which you're rarely sure what time of day it is (and even when you are, your body doesn't agree).

Strange things happen at the edge of sleep - funny jerking movements, illusions of falling and even hallucinations. Then there is the phenomenon of microsleep, which circadian physiologists define as the state of "being asleep without being perceptually aware of that fact". Sounds terrifying, doesn't it? Very bad if you are at the wheel of a fast-moving vehicle, not great if you're a neurosurgeon up to your armpits in somebody's frontal lobes and even worse if you find yourself standing in front of 30 undergraduate students with a board marker in your hand unsure of the content of the last sentence you just uttered.

The good news is that you can reduce the incidence of microsleep by napping whenever you get the chance. The US space agency Nasa has researched this.

Pilots have known about the value of a catnap for some years - it may disturb you to realise that half the flight deck of your 747 could be having a snooze while you're at 36,000ft over the Atlantic, but it's probably safer overall.

Power napping, however, is just a sticking-plaster solution. Apparently, if you feel sleepy during the daytime, even during stimulating activities, you're probably sleep deprived. Chronic sleep loss appears to cause problems with your immunity, increases your chances of developing diabetes and, as charmingly put by one researcher, brings "a modestly increased risk of all-cause mortality". The lessons are clear. Get a decent night's sleep. There's no substitute.

Last year, I got the feedback forms from the students at the end of the course. Searching through the comments made about the lectures I had given, I found one for my talk that simply said: "Content OK, but that bloke really should try to get more sleep." Which just goes to show that you can learn as much from them as they do from you.

Kevin Fong is a physiology lecturer at University College London, a junior doctor and chairman of the UK Space Biomedical Research and Education Advisory Committee of the British National Space Centre.