Too Much Sleep Can Kill

Author:  Metcalfe David
Date:  October 2007

It is common knowledge that too much sleep kills thousands of people at the wheel of their car every year. Now, scientists have shown that, while lack of sleep doubles the incidence of death from cardiovascular disease, excessive sleep can also increase the risk of death from other causes. According to data presented to the British Sleep Society this month by Francesco Cappuccio, Cephalon Professor of Cardiovascular Medicine at the University of Warwick, career changes and leisure pastimes have "meant that reports of fatigue, tiredness and excessive daytime sleepiness are more common than a few decades ago." Furthermore, "sleep represents the daily process of physiological restitution and recovery, and lack of sleep has far-reaching effects."

The researchers analysed the mortality of 10,308 civil servants in addition to their sleep patterns at two different points in their life, between 1985-1988 and 1992-1993. The data was adjusted to eliminate a range of potentially confounding factors such as age, sex and employment grade. Once they had controlled their data for these factors, the researchers were in a position to isolate the effect of sleep duration on the mortality of their study participants.

As might be expected, the researchers found that those sleeping for five hours a night were twice as likely to die as a result of cardiovascular disease. Cappuccio has indicated that "short sleep has been shown to be a risk factor for weight gain, hypertension and type 2 diabetes, sometimes leading to mortality." However, those sleeping for eight hours or more were also twice as likely to die as those sleeping for seven hours. It remains unclear, however, why excessive sleep might be associated with increased risk of death. According to Cappuccio, "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."

Author: David Metcalfe

Reviewed by: Andrew Wang

Published by: Konrad Sawicki