The authors of a Japanese study evaluated various factors that they thought could be associated with lumbar intervertebral disc degeneration. Lumbar intervertebral discs degenerate with normal aging. Degeneration of discs precedes lumbar disc herniation and lumbar spinal canal stenosis. Using magnetic resonance imaging, MRI, they were able to evaluate 1,347 intervertebral discs from L1/2 to L5/S1 in 270 subjects with a mean age of 68.4 years who volunteered for the study.
Recent studies have determined that heredity plays a role in degenerative discs. The authors were interested in acquired factors that could be associated with degeneration of discs since they can be modified. Prevention by improvements in lifestyle could reduce degeneration of discs, and associated lumbar degenerative diseases. The authors sought to clarify the associations between identified disc degeneration according to MRI, and suspected risk factors including atherosclerosis and cardiovascular risk factors. Other acquired factors considered in the study included body mass index, body mass density, occupation, participation in sports, smoking, and alcohol use.
Atherosclerosis was evaluated using pulse wave velocity, PWV. This is a measurement of the speed a pulse travels between two points. The greater the resistance of the blood vessel, the faster the speed. Lipids and glycosylated hemoglobin were measured from blood samples. Body mass index was calculated using height and weight of the subjects. Ultrasound of the heel or calcaneus was used to determine BMD. Questionnaires and telephone interviews asked the following questions. Have you ever experienced low back pain, LBP, during your lifetime? Do you smoke cigarettes? Do you drink alcoholic beverages? Have you ever engaged in an occupation that involved lifting weights of more than 10kg for more than one third of your working hours? Have you worked as an occupational driver? Have you ever participated in a sport more than three times per week for more than five years, and if so, what kind of sport?
The degree of disc degeneration was evaluated with MRI using the Pfirrmann grading system. However, because in this older population, the signal intensity and disc height measurements did not correlate well, the authors chose to use signal intensity as the most accurate measurement of disc degeneration. The authors analyzed each level separately. Results indicated that aging was correlated with degenerative discs from L1/2 to L4/5; high BMI with degeneration at L2/3, L3/4, and L5/S1; high low density lipids with L4/5 and L5/S1 disc degeneration; high PWV with L1/2 and L2/3; low BMD with L5/S1; occupational lifting with L1/2 and L4/5; and sports with L5/S1. Gender, triglycerides, glycosylated hemoglobin, history of LBP, current smoking and drinking habits, and occupational driving had no correlation to degenerative discs. The authors note that the sample size of smokers was likely too small for statistical accuracy.
The authors conclude that prevention of acquired risk factors such as high BMI, high LDL cholesterol, occupational lifting could affect the onset of degenerative discs and lumbar degenerative diseases.
M. Hangai et al. Factors associated with lumbar intervertebral disc degeneration in the elderly. Spine J. September 2008. Volume 8. Issue 5. Pp 732-740.