See the MRI’s here? It’s an office worker on left and truck driver on right. Twin siblings 56 years old. They show high degrees of similarity in disc degeneration despite high differences in their lifetime physical exposure to loading.
The findings of the Twin Spine Study, an ongoing research program started in 1991, have led to a dramatic paradigm shift in the way disc degeneration is understood. In the past, the factors most commonly suspected of accelerating degenerative changes in the discs were various occupational physical loading conditions, such as handling of heavy materials, postural loading and vehicular vibration.
Drawing on information from 600 participants in the population-based Finnish Twin Cohort–147 pairs of identical and 153 pairs of fraternal male twins–the Twin Spine Study has turned around the “injury model” approach to disc degeneration.
Researchers from Canada, Finland, the United States and the United Kingdom compared identical twin siblings who differed greatly in their exposure to a suspected risk factor for back problems; for example, one of the twins had a sedentary job while the other had heavy occupational physical demands, or one routinely engaged in occupational driving while the other did not. The studies yielded startling results, suggesting that genetics play a much larger role in disc degeneration than we previously thought.
The findings indicated that while physical loading–handling heavy loads, bending, twisting and static work in awkward postures–appears to influence disc degeneration, the effects are very modest. The Twin Spine Study is far from over: having found evidence that genetics may play an overlooked role in disc degeneration, the team of North American and European is now working to identify the specific genes and biological mechanisms influencing disc degeneration and back pain problems; understanding how degeneration progresses over time; and differentiating normal, inconsequential changes from degenerative changes that lead to pain.
What’s the take home point here? I think it’s not that your life can be a physical loading free for all and the stressors you put on your spine don’t matter — they do. Trauma and repetitive strain can certainly have an effect on the degenerative process. However, family history is more likely than once thought to be a risk factor for spinal problems — or resistance to spinal problems. In other words, if you are among the 20% of the population who does not experience some form of low back pain in their lifetime, thank your genetics (and your parents).
Dr. Brett L. Kinsler is a chiropractor serving the greater Rochester NY area.