Lonely people are more likely to get sick and die young, and researchers said on Thursday they may have found out why — their immune systems are haywire.
They used a "gene chip" to look at the DNA of isolated people and found that people who described themselves as chronically lonely have distinct patterns of genetic activity, almost all of it involving the immune system.
The study does not show which came first, the loneliness or the physical traits. But it does suggest there might be a way to help prevent the deadly effects of loneliness, said Steve Cole, a molecular biologist at the University of California Los Angeles who worked on the study.
"What this study shows is that the biological impact of social isolation reaches down into some of our most basic internal processes — the activity of our genes," Cole said.
"We have known for years that there is this epidemiological relationship between social support — how many friends and family members you have around you — and a whole bunch of physical outcomes," he said in a telephone interview.
Many studies of large populations have shown that people who describe themselves as lonely or as having little social support are more likely to die prematurely and to have infections, high blood pressure, insomnia and cancer.
"There are two theories — the social provision theory, which basically is about what other people do for you in a tangible, material sense. Like, if I am sick and I have got people around me, they will take me to the doctors, they will see I take my pills," Cole said.
"The other is that there is something about being isolated and lonely that changes your body."
His team set out to investigate the second theory.
All the lonely people
John Cacioppo, a psychology professor at the University of Chicago, has been studying the health effects of loneliness for years in a group of people who have allowed him to delve in-depth into their social lives and health.
Cole and Cacioppo's team studied 14 of these volunteers — six who scored in the top 15 percent of an accepted scale of loneliness.
"These are people who said for four years straight 'there's really nobody that I feel that close to'," Cole said.
The other eight were the least lonely of the group.
Cole's team took blood and studied the gene activity of their immune system cells — the white blood cells that protect from invaders such as viruses and bacteria.
All 22,000 human genes were studied and compared, and 209 stood out in the loneliest people.
"These 200 genes weren't sort of a random mishmash of genes. They were part of a highly suspicious conspiracy of genes. A big fraction of them seemed to be involved in the basic immune response to tissue damage," Cole said.
Others were involved in the production of antibodies — the tag the body uses to mark microbes or damaged cells for removal, Cole said.
The findings suggest that the loneliest people had unhealthy levels of chronic inflammation, which has been associated with heart and artery disease, arthritis, Alzheimer's and other ills.
The next step is to see if this might be treated, Cole said. "This is a biological target for intervention," he said. "Maybe we can give these people aspirin."
Aspirin, an anti-inflammatory drug, is also a blood thinner taken regularly by many people to prevent heart attacks and stroke.