Sleep disturbance is associated with a variety of health consequences. For seniors, a new study has found that poor sleep may contribute to the rise of stroke and dementia.

A group of Canadian researchers suggests that sleep fragmentation, which is defined by waking episodes several times during the night, is connected to little brain changes that can only be observed in autopsies.

What the experts found was that the more severe the sleep fragmentation, the higher is the risk of small brain arteries to harden. They also discovered that a person's risk of brain tissue death due to little oxygen in small strokes increases as sleep fragmentation becomes worse.

Although sleep disturbances have been associated with stroke in the past, few researches have delved into the relationship between sleep and the deep histopathology of stroke. With this, the authors of the new study tested their hypothesis that higher sleep fragmentation is connected to increased brain vessel damage and lack of oxygen as observed via autopsies.

To do that, the researchers studied the autopsied brains of 315 subjects, who had an average age of 90 years old. The participants had at least a week of sleep quality evaluation before they died. The authors noted that 29 percent of the participants had a stroke and 61 percent suffered from moderate-to-severe damage of brain blood vessels.

The authors found that the average waking times in all the participants were seven times in an hour, but some had additional waking episodes during that period.

The results of the study show that those with the highest degree of sleep fragmentation were 27 percent more prone to have hardened brain arteries. Those who had two more additional arousals were found to have a 30 percent more chance of exhibiting observable signs of lack of oxygen in the brain.

Lead author Andrew Lim from the University of Toronto says that it is possible for the repeated waking episodes to increase blood pressure, which in turn could damage the blood vessels.

Lim, however, said that the study findings do not offer a cause-and-effect relationship between sleep and stroke.

"At this point in time we don't have hard evidence that treating sleep fragmentation is going to make a big difference," he said.

He further explained that sleep fragmentation may disrupt brain circulation or vice-versa, and both may also be caused by another underlying factor. With this, the study results may not exactly tell which is which. The authors said, however, that their work signifies that the brain changes they observed were tied to strokes and dementia.

For now, Lim said experts need to investigate deeper about the root and other aspects of sleep fragmentation that causes the most severe brain impairments.

Whatever the actual explanation may be, this study serves as another reason to improve sleep quality, especially as a person advances in age.

The study was published in the journal Stroke on Thursday, Jan. 14.

Photo: Allen Lai | Flickr