A study was presented at the American Heart Association meeting where almost 70,000 female nurses were asked how long they slept on average over a 20 year span of time. The researchers than recorded which women had a stroke and analyzed if a certain number of hours of sleep increased the risk of stroke relative to the baseline average of seven hours per night.
The researchers found that women who slept 10 or more hours had a 63% increase risk of stroke. Those women that slept less than 7 or 8-9 hours per night had an insignificant increase in stroke risk. Of note, the researchers adjusted the risk for other factors like alcohol intake, fruit and vegetable consumption, physical activity, and smoking status. Body mass index and the presence of diabetes and high blood pressure were recorded as potential influential factors.
The researchers were unable to determine any underlying biological mechanism that could cause the increased risk of stroke in longer sleepers.
I wonder if some of the women have untreated sleep apnea, which can cause longer sleep durations, in an attempt to get more rest. Untreated sleep apnea does increase the risk of stroke.
Longer sleep durations could mean that these women have brains that function differently or are structurally different, and perhaps those differences could account for the increased stroke risk.