A new study finds that sleeping either too much or too little heightens the risk of stroke.

The researchers reported their findings applied only to the postmenopausal women in the study but other experts claim that the relationship between sleep and stroke seems to be universal.
The study included over 93,000 women and showed that those who slept for more than nine hours a night had a 60 % - 70 % higher risk of stroke than women sleeping seven hours. Also, the risk of stroke was 14 % higher for women who slept six hours or less.

A couple of previous studies have reported adverse effects of sleep deprivation and the last one adds to that evidence.
Many other studies have also showed a connection between abnormally long sleep and a higher risk of cardiovascular disease and high blood pressure.

The link between sleeping too much or too little and the stroke risk cannot be explained by traditional risk factors such as cholesterol levels or high blood pressure.

It is not yet clear why and how sleep increases stroke risk, but there are a few possible explanations. One is that those people who sleep long hours may have "ineffective sleep," meaning that their sleep is broken up by unnoticed wakening like with a breathing disorder called sleep apnea.
Other explanation may be in the patient's psychosocial profile. It is known that depressed people tend to sleep longer.

It is both sleep and the quality of sleep that are important for survival.
As far as too little sleep goes, it is known that sleeping less than six hours may affect a woman's hormonal system by releasing many stress hormones.

The researchers report that setting the clock to sleep an allotted amount of hours may not solve the problem. Those women who are not sleeping long enough should try stress reduction or other methods to get more sleep. In case of long habitual sleeping patterns, women should consult their doctors and act to lower the known risk factors for stroke, like high blood pressure.