Baseline blood samples were taken from all participants, who were then subjected to stress they were asked to deliver an impromptu five-minute speech and perform a mental arithmetic task in front of a video camera and three panelists. Researchers followed by stimulating the participants' immune systems with lipopolysaccharide, a compound found on bacterial cell walls that is known to trigger an immune response.
In both populations, those who were lonelier produced significantly higher levels of a cytokine called interleukin-6, or IL-6, in response to acute stress than did participants who were more socially connected. Levels of another cytokine, tumor necrosis factor-alpha, also rose more dramatically in lonelier participants than in less lonely participants, but the findings were significant by statistical standards in only one study group, the healthy adults.
In the study with breast cancer survivors, researchers also tested for levels of the cytokine interleukin 1-beta, which was produced at higher levels in lonelier participants.
When the scientists controlled for a number of factors, including sleep quality, age and general health measures, the results were the same.
"We saw consistency in the sense that more lonely people in both studies had more inflammation than less lonely people," Jaremka said.
"It's also important to remember the flip side, which is that people who feel very socially connected are experiencing more positive outcomes," she said.
|Contact: Lisa Jaremka|
Ohio State University