April 10, 2001 CHICAGO (AP) - Scientists have identified a genetic mutation that significantly raises the risk of sciatica, one of the most common causes of back pain.
In the study, people with the mutation were three times more likely than those without it to have sciatica, a spinal disk disease that affects the body's largest nerve and causes pain in the lower back and legs.
Sciatica affects about 5 percent of adults in the United States and Finland, the researchers said. It is one of the most common causes of chronic disability.
The study by researchers in both countries appears in Wednesday's Journal of the American Medical Association.
The mutation is a variation of one that the researchers previously found is present in about 4 percent of patients with sciatica. The new findings suggest that the variation is about six times more common.
Sciatica has been linked to environmental factors such as improper lifting and sitting for long periods. The new findings suggest that people with the genetic variation are especially vulnerable to such stresses, said Dr. Leena Ala-Kokko, who led the research at the University of Oulu in Finland. She is now with Tulane University.
The variation can be found in a relatively simple blood test, offering a new way to diagnose sciatica, which often does not show up on MRI scans, Ala-Kokko said.
Ala-Kokko and colleagues collected blood samples to obtain DNA from 171 people in Finland with sciatica. The researchers also looked at a comparison group of 321 Finns without the disease.
The mutation was found in about 24 percent of the sciatica patients and 9 percent of the comparison group. Ala-Kokko said that suggests some of the comparison-group patients may have had sciatica but had not yet developed symptoms.
The mutation is thought to damage a protein in the disk called collagen IX. This can make the disk prone to rupture, sometimes resulting in pressure on the sciatic nerve, which runs from the pelvic area down each leg.
In an accompanying editorial, Dr. Joan C. Marini of the National Institute of Child Health and Human Development, said further study of the interplay between genes and physical stress is needed to help find ways to prevent and treat disk disease.
Copyright 2001 The Associated Press. All rights reserved.
