New research shows that aging women who
sleep well and/or have strong social ties have lower levels
of interleukin-6, an immune system protein that promotes
inflammation and that tends to increase with age.
Interleukin-6 (IL-6) has been linked to a variety of
diseases including osteoporosis, rheumatoid arthritis,
heart disease, Alzheimer's disease,
and cancer. People who have relatively high levels of
IL-6 are at greater risk for these diseases.
"The bottom line" said Dr. Elliot M. Friedman, "is that
while poor quality sleep and low quality social relationships
increase the risk of higher levels of IL-6 and, thereby,
age-related disease, you don't need to have both in order
to have low levels of IL-6 -- having high levels of one
is enough."
Friedman, from the University of Wisconsin in Madison,
and colleagues examined the interplay between social engagement,
sleep quality, and blood levels of IL-6 in 74 women between
the ages of 61 and 90. The team reports their research
in the early online issue of the Proceedings of the
National Academy of Sciences.
"Our goal was to find out if there are psychological
factors that might protect people against high levels
of IL-6 as they age and we had two interesting findings,"
Friedman stated.
"First, we found that sleep quality and social relationships
appear to be protective against high levels of IL-6, even
after accounting for other factors that could affect IL-6
levels, such as chronic illness, obesity, and smoking,"
he reported. Women who slept well had low levels of IL-6,
as did women who reported strong social relationships,
Friedman further explained.
But having either good social relationships or good sleep
quality appears to compensate for difficulties with the
other. That is, IL-6 levels were only higher in women
who slept poorly and who reported poor quality social
relationships.
The researcher admitted that he was surprised by this
compensatory relationship. "I would have expected an additive
effect: that is having both good sleep and good social
ties would be better than having one or the other, and
having one would be better than having neither."
The fact that good social ties can compensate for poor
sleep, and vice versa, suggests a more complex relationship
between these psychological and biological factors --
"which also means that we have lots more exciting work
to do to figure out why this is," Friedman said.
SOURCE: PNAS Early Online Edition, December 5, 2005.
