The presence of chronic back pain is associated with a loss of gray matter in the brain similar to that seen in the normal aging process, new research suggests.

Because, by definition, chronic pain has adverse effects on mood and increases stress, one explanation is that tissue atrophy is caused by toxic and inflammatory mechanisms, lead author Dr. A. Vania Apkarian, from Northwestern University Institute of Neuroscience in Chicago, said in a statement.

As reported in the Journal of Neuroscience, Apkarian’s team used magnetic resonance imaging (MRI) to compare the brains of 26 patients with chronic back pain with those of 26 matched “controls” without such pain.

Gray-matter volume was reduced by up to 11 percent in back pain patients compared with controls, the investigators found. They estimate that between 10 and 20 years of normal aging would be needed to see this amount of loss.

A direct association was noted between pain duration and gray matter loss. For each year of chronic pain, a 1.3-mL drop in gray matter volume occurred, the authors point out.

This is the first study to show brain tissue abnormalities in patients with chronic pain, the researchers note.

It will be important in future studies to correlate gray matter changes with specific types of chronic back pain, which may help to better characterize this brain loss, they add.

SOURCE: Journal of Neuroscience, November 23, 2004.