Occasional nights of sleep being disrupted, perhaps because of anticipation of the following day (a new job, a holiday etc.) are not too bad for the body, especially if the excitement of the next day's activities counters the effects.

Monotonous tasks may be at risk, and reaction time is slowed. Creative thinking might be blurred, but the effects are not usually critical. The effect is more noticeable in boring tasks but in an emergency, adrenaline keeps us going.

Missing sleep chronically is a different matter.

"The insomnia had begun to pervade every aspect of his life, the way the smell of frying garlic on the fifth floor will eventually pervade an entire apartment building."
Stephen King, "Insomnia".

Lack of sleep is cumulative.

Even small losses over a period of time have major impact on attention, memory, mood, thinking ability, behaviour, and of course, safety.

"Insomnia is much more than losing a few nights' sleep"
Dr. Michael Bonnet, sleep researcher, 1995.

People with chronic insomnia have increased metabolism (compared with normal subjects who have been deprived of sleep, whose metabolism slows down).

They tend to experience increased anxiety and agitation, whereas normal people with a few nights' disturbed sleep become lethargic and less responsive. Normal sleepers don't have trouble catching up on their sleep, but insomniacs do.

At the 2001 Paris workshop on sleep, one American expert stated that poor sleepers are more than twice as likely as good sleepers to have ischaemic heart disease in the first six years after experiencing sleeping difficulties, and they are about three times as likely as good sleepers to develop frequent headaches.

The risk of depression is four times greater in insomniacs than in normal sleepers and 25-40% of insomniacs experience significant anxiety. The abuse of alcohol and other substances is also more prevalent in insomniacs.

A recent study, published in the journal "Sleep" in August, 2002 (), found that patients were not only experiencing night-time symptoms frequently (sleep disturbance, environmental sensitivity) but also day-time problems such as difficulty thinking and sleepiness (1).

Those with depression related insomnia experienced more severe symptoms, which correlated with the number of hours slept. The authors concluded: "Night-time and daytime symptoms need to be assessed together when measuring insomnia severity."

In an online interview on insomnia Dr. Rosenberg, a sleep expert, echoed this when he stressed that "sleep and wake is a 24-hour cycle and you have to examine not only what's going on at night, but what's going on in the daytime."
(the whole interview is available at :

http://talkaboutsleep.com/print_versions/disorders/insomnia/Prinsomnia_interview.htm )