Both sleeping well and having good quality social relationships predict lower levels of IL-6, a molecule linked to diseases ranging from Alzheimer's to rheumatoid arthritis to cancer.

It's been known that poor sleep quality is associated with higher levels of IL-6, which in turn are associated with higher death rates, said Friedman, a Robert Wood Johnson health & society scholar.

"But the idea that good social relationships can compensate for poor sleep is new," he said.

The findings appear in this week's issue of the Proceedings of the National Academy of Sciences.

Good Quality Social Relationships

Friedman isn't dispensing advice based on the finding because the study was rather small. It included 74 women, aged 61 to 90, who filled out questionnaires about their social engagements, wore equipment that monitored their sleep at home, and gave blood samples for IL-6 testing.

"It's an intriguing result," he said. "Now we need to expand it to men, and more women as well."

Friedman said he's been studying "what kind of psychological processes seem to be able to influence biological markers that are linked to disease." But while studies by other researchers have looked at negative indicators, such as stress or depression, he has been looking at positive indicators.

The new study was designed to test "a specific hypothesis, why good quality social relationships are beneficial," Friedman said. "It's possible that they help people sleep better. People who are lonely don't sleep as well. And if they don't sleep well, they have higher levels of IL-6 in the blood."

As it turned out, the study showed that "both sleeping well and having good quality social relationships predict lower levels of IL-6," Friedman said. "Either one or the other is beneficial. Only in women who have neither do we see higher levels of IL-6."

While the study indicated that "it's nice to have friends and it's important to sleep well," Friedman said he's "circumspect about jumping to conclusions."

"What is it about social relationships that affect biology?" he said. "Once we get a handle on that, the practical applications can become more clear."

Biological Factors

What is clear is that it never hurts to have friends, Friedman said.

"It has been known for many years that being socially isolated predicts early mortality," he said. "What we see is, not just being lonely but improving the quality of friendships can improve biological factors as well."

The study was welcomed by Dr. Alexandros N. Vgontzas, a professor of psychiatry and a sleep researcher at the Penn State College of Medicine, in part because it confirms his previous research linking sleep with IL-6 levels. "To see this thing being confirmed shows that it is real," he said.

But the study also adds "important new information" about social interactions and sleep, Vgontzas noted. "It indicates that these two things, psychological well-being and sleep, go hand in hand," he said.

More information: For more on women and health benefits of friendships, visit Oregon State University.