Dr Shapiro, Professor of Psychiatry at the University of Toronto, says that women may be affected by the same syndrome identified in shift workers who have been found to suffer disturbed sleep 10 years after stopping night work.
'It is speculative but plausible that the higher incidence of complaints of insomnia in middle-aged and older women is a consequence of long-standing disrupted sleep at a time when the sleep drive is most strong which produces its effects 15 to 25 years later,' he says in the ABC of Sleep Disorders, a compilation of recent research reports. At the same time, 'the erosion of sleep time in adolescents - almost 20 per cent this century - may have a profound and long-lasting impact on society if these adolescents are more sleepy and less able to learn.'
Philosophers and doctors have long wondered about the significance of dreams, but current research suggests that dreaming may reflect the presence of an illness and even cause or precipitate disease.
Research has found that men with cardiac disease are prone to dreams about dying, while dreams of lost resources have been linked to loss of brain cells, measured by scans, in elderly people. These findings were not influenced either by the patients' anticipation of 'the worst' or to awareness of their disability.
Another study reported that patients who did not dream at all were the most likely to die. 'It has been hypothesised that dreams 'warn' medically ill patients whose illness is seen as both threatening to the body and the ego; when however the threat becomes too severe the dreams disappear altogether.'
Although drugs to help people sleep cost more than pounds 27.5m a year and nearly 23 million NHS prescriptions are written for insomnia annually, Professor Shapiro says Britain is far behind the US in sleep research. In America, one in seven people has a 'chronic sleep-wake' disorder. He says that in India where poverty has profound effects on sleep, it is estimated that one-third of the population goes to sleep when standing up.
It has long been recognised that fatigue accompanies many illnesses and it emerges in the book that there is a complex relationship between sleep, illness and recovery.
Little work has been carried out on humans. But rats deprived of sleep develop septicaemia and rabbits infected with a common bacteria experience sleep disturbance.
One US estimate puts the price of sleep problems at dollars 16bn annually through loss of productivity and increased medical costs.
ABC of Sleep Disorders; edited by Colin M Shapiro; British Medical Journal Publishing Group; pounds 12.95Reuse content