Chronic Back Pain. Basically they took 26 people with chronic back pain. For every year of chronic back pain they had an average loss of 1.3 cm cubed loss of gray cortical matter. Patients with chronic back pain had 5-11% less neocortical gray matter volume than control subjects. This amount was the about the amount of the gray matter volume lost in 10-20 years.
I'm sure with most studies you have to consider a few things. There is awesome new research showing how exercise and aerobic fitness can increase new brain synapses and brain health. So the first thing that comes to mind is were these subjects sedentary? Could the lack of movement or exercise, if it was applicable, contribute a large portion to the decrease gray matter rather then just the chronic pain?
Either way, chronic back pain is something that should not be put up with. Find some help. Get a good hands on manual therapist and start incorporating smart exercises that will help the back for the long term.