New research suggests that social isolation can increase the chances of dying after a stroke.
According to the study, loneliness may promote more damaging inflammation in the brain during a stroke.
Researchers at Ohio State University found that all the male mice that lived with a female partner survived seven days after a stroke, but only 40 percent of socially isolated animals lived that long.
In addition, the paired mice suffered much less brain damage than did the surviving solitary mice.
"Under nearly every measure, it seems that there was something about living together that protected the mice by reducing the damaging inflammatory response," said Kate Karelina, lead author of the study and a doctoral student in neuroscience at Ohio State University.
In a series of experiments, Karelina and her colleagues induced experimental strokes in male mice. Some of the mice lived with a female partner for two weeks before the stroke and continuing afterwards. Other mice lived alone before and after the stroke. A control group of mice underwent similar surgery in the brain, but did not have an induced stroke.
The reasons for the higher survival rate for the socially housed mice were evident when the researchers compared brain tissues of mice after the stroke.
The researchers examined tissue samples in different groups of mice 12 hours, one day, three days or seven days after the stroke to determine the extent of damage.
"We confirmed that that social isolation contributes to the extent of neuronal damage in the brain as early as 24 hours after the stroke," said Courtney DeVries, associate professor of psychology and neuroscience at Ohio State, and a member of the university's Institute of Behavioral Medicine Research.
The amount of tissue damage in the brain was about four times larger in the mice housed alone compared to those housed with another mouse.
"The number of neurons dying is significantly decreased in the pair-housed mice," DeVries said.
In addition, socially housed mice had significantly less edema, or excess water in the brain, when compared to the isolated animals.
"In clinical stroke, edema is a major concern because it can lead to additional neuronal damage, so it is significant that pair housing reduced edema," Karelina said.
The study showed that two genes associated with damaging inflammation in the brain, MAC-1 and glial fibrillary acidic protein, or GFAP, showed decreased activation in the socially housed mice.
In addition, findings revealed that mice that lived with others had significantly higher levels of a cytokine in their brain called interleukin-6 (IL-6) that has an anti-inflammatory response in the brain, helping to limit damage caused by the stroke.
The study is due to be published in the Proceedings of the National Academy of Sciences.