Inflammation Can't Explain Depression's Link to HeartDisease

Inflammation Can't Explain Depression's Link to HeartDisease
THURSDAY, Nov. 15 (HealthDay News) -- Depression is known to hikethe risk of cardiovascular disease, but don't put all the blame on anyconcurrent rise in inflammation.
So concludes a study led by Dr. Viola Vaccarino, a professor ofmedicine at Emory University, in Atlanta.
That means that it's back to the drawing board in terms of unravelingthe depression-heart disease link, according to Vaccarino.
"That depression is a factor in cardiovascular disease is clear. Whatis not clear is what kind of mechanism is involved," she said.
The Emory group, as well as researchers from five other medicalinstitutions, studied the possible role of inflammation in a group of 559women who were referred for heart tests because of blockage in a coronaryartery. All the women had a standard test for depression at the start ofthe study and were followed for an average of about six years.
They were divided into three groups on the basis of those tests: thosewho clearly were depressed by diagnosis and previous treatment; those whomight be depressed because of either a diagnosis or treatment; and thosewho had no indicator of depression.
The researchers made frequent measurements of two molecules linked tothe inflammatory response -- C-reactive protein (CRP) andinterleukin-6.
There were 79 major events of cardiovascular disease during the study,23 of them fatal.
As expected, the incidence of such events was 2.5 times higher in womenwith depression. There was no comparable increase in women classified aspossibly depressed.
The team found that women diagnosed as depressed had a 70 percenthigher level of C-reactive protein and a 25 percent higher level ofinterleukin-6 compared to women who were not depressed. Women classifiedas possibly depressed had elevated levels of both markers, but to a lesserextent.
The bottom line, according to the researchers, was that whileinflammation was tied to heart risk, it failed to explain most of thecardiovascular danger posed by depression.
"Despite being associated with each other, depression and inflammationpredicted future events for the large part independently," the researcherswrote. "Thus, despite a clear relationship between depression andinflammation, the latter plays only a minor role in the higher risk ofadverse outcomes for women with depression."
The finding is something of as surprise, said Dr. David S. Sheps,professor of medicine at the University of Florida at Gainesville, amember of the research team.
"We know from other studies that there is a relationship betweendepression and elevation of certain inflammatory molecules, but no oneknows for sure what the mechanism is," Sheps said.
"What is clear is that inflammation does not play a substantial role,"Vaccarino said. "We need to look at other things. Perhaps there is achange in the ability of platelets to aggregate." Platelets are bloodcells that can form clots to block arteries. "And there could be otherpathways," she said.