Too much sleep as dangerous as too little: study

Last Updated: Monday, September 24, 2007 | 10:47 AM ET

CBC News

Sleeping too much, just like sleeping too little, could be linked to a person's risk of an early death, a new British study indicates.

Researchers at the University of Warwick's Warwick Medical School studied 10,308 British civil servants in two different time periods: between 1985 and 1988, and between 1992 and 1993.

Study participants who upped their nightly sleep to eight hours or more were more than twice as likely to die within the ensuing 11-17 years as those who kept sleeping for seven. Researchers believe depression, low socioeconomic status and cancer-related fatigue could play a part.
(CBC)

With seven hours seen as the optimal amount of sleep for the average adult, the study subjects who cut the duration of their sleep from seven hours to five hours a night had a 1.7-fold increased risk of death from all causes within the ensuing 11-17 years, according to the research, presented Monday to the British Sleep Society.

They also had twice the increased risk of death from a cardiovascular problem.

More surprisingly, scientists found those individuals who increased the number of hours they slept per night from seven to eight hours or more were more than twice as likely to die within 11-17 years as those who kept sleeping for seven. They were more likely to die from non-cardiovascular diseases.

"Short sleep has been shown to be a risk factor for weight gain, hypertension and Type 2 diabetes sometimes leading to mortality," said Francesco Cappuccio, an author of the study.

"But in contrast to the short sleep-mortality association, it appears that no potential mechanisms by which long sleep could be associated with increased mortality have yet been investigated. Some candidate causes for this include depression, low socioeconomic status and cancer-related fatigue."

Cappuccio said adults should aim for seven hours of shuteye a night.

"In terms of prevention, our findings indicate that consistently sleeping around seven hours per night is optimal for health and a sustained reduction may predispose to ill-health."