There are a lot of articles around about the causes of type-2 (late onset) diabetes.

Missing the obvious fact it’s almost always about the balance between diet and exercise, a variety of factors are adduced for this tiresome disease.

Did you know that both lack of and too much sleep can tip you over the edge? Either option can make you far more likely to develop diabetes, according to researchers at the Universite Laval in Quebec, Canada. The results are published in the journal, Sleep Medicine.

Optimum sleeping times are seven to eight hours a night, they say. If you undershoot or exceed that, you are two and a half times more likely to suffer blood sugar abnormalities.

Researcher Angelo Tremblay says, “The risk remains significant even after a statistical adjustment for body mass index and waist circumference. … It is clear the recommendation to seek an optimal sleep duration seems to be appropriate, but for some individuals it is easier to say than do.”

One factor that isn’t mentioned is the differences between individuals. Such research often assumes that everyone’s reaction to stress is identical. It isn’t.

What’s your idea of a good night’s sleep? Is it seven, eight, nine, or even 10, or more, hours?

Well, it could be much less.

According to some authorities sleep is much overdone in modern times. Our ancestors made do on much less slumber at night. They were partly nocturnal and made up by napping for a few hours during the day.

The problem is that when we sleep, parts of our consciousness leave the physical envelope of the body. If that period is too long, it causes muscle inflexibility and, in some cases, lower mental performance.

It’s a well-known fact that an hour’s nap in the afternoon boosts our energy and overall thinking skills. NASA, which has studied the performances of astronauts in space, believes that a nap during the day is of immense benefit to everyone.

The optimum pattern of sleep would be four or five hours at night, plus a two-hour nap during the afternoon.

If pressures of work make that impossible, any system of splitting sleep up to reduce one big slab of unconsciousness will be beneficial.

For example, two periods of three hours is preferable to one of eight hours.

As people differ in their requirements, it’s a good idea to experiment with your personal needs, but a split sleep pattern may well deliver enormous benefits to your life.

New research confirms that a short afternoon nap can make a major difference to your work performance and health, especially if you’re involved in mental work.

A new book by Harvard University sleep expert Dr Sara Mednick, Take a Nap! Change Your Life, describes the simple process of taking a nap as a “lifesaving habit”. She claims that snoozers make fewer mistakes and have boosted brainpower. One of her experiments involved one group taking a nap, another group drinking a mug of coffee (200mg of caffeine), and a control group taking a placebo (an inert substance).

They were then given a series of tasks, including typing and spatial skill tests. The coffee drinkers performed much worse than the placebo takers, while the nappers performed best of all. So the common assumption that coffee will keep you going through the day is a myth — or probably fed to us by the coffee industry.

Dr Mednick, a psychologist and research scientist, has accumulated a lot of evidence that a simple siesta in the afternoon is the best medicine for a happier, healthier life. People who sleep for 30 minutes at least three times a week had a 37pc lower chance of a heart attack, according to a lead researcher from the Harvard School of Public Health.

In another study, recently published in Nature Neuroscience journal, the good doctor put 30 well-rested people through the same set of tasks four times in the course of a day, starting at 9am through to 7pm — a typical working day for freelances and the self-employed.

Performance dropped by 50pc in those who stayed awake all day. However, the volunteers who took an afternoon nap kept up their performance throughout the day.

NASA –as you might expect — gets in on the act. Tests conducted by them show that astronauts who took a brief snooze doubled their alertness even if they were not tired before the nap. They also increased their work productivity by at least 13pc.

The ideal time to nap apparently is between 1pm and 3pm which enables the most restful kind of sleep pattern for boosting performance.

That’s it, I’m off to take a nap.