conducted by researchers at the University
of North Carolina, found
that sleeping longer — nine hours to be exact — increased the risk of stroke in
post-menopausal women by 60 to 70 per cent over those who slept seven hours.
accounting for all common clinical conditions predictive of stroke, we found
this increase was statistically significant: sleeping nine hours or more is
strongly associated with increased risk of ischemic stroke," said lead
author Jiu-Chiuan Chen, assistant professor of epidemiology at the University
of North Carolina's School of Public Health in Chapel Hill, in a release.
At the same time
sleeping less than six hours meant the women were 14 per cent more at risk of
stroke than those sleeping seven hours.
The 93,676 women
in the study — who were between 50 and 79 years old and enrolled at 40 U.S.
clinical centres — were asked how many hours they slept at night.
said because women usually get less, rather than more, sleep, the risk of
stroke stemming from sleep deprivation is likely of more concern than the one
caused by oversleeping.
They say they are
unsure as to why the longer sleepers were more at risk of stroke.
observed increase in stroke risk in long sleepers may be due to some unmeasured
factors, such as undiagnosed sleep disorders, although we did attempt to
account for that in our analysis."
Chen called for
further study into the mechanisms affecting stroke risk.
published Friday in the Journal of the American Heart Association, was
conducted between 1994 and 2005.