It seems to be accepted conventional wisdom that gravity has many harsh effects on the human body as we age. Dr. Videman, MD and PhD out of the University of Alberta and his team of researchers attempt to dispel the myth that spine compression causes the shortening of the human stature. Prior research has long focused on either the flattening disc as a culprit in back pain problems, or the deteriorating vertebral body, but very few studies have examined both structures and their relationship. In other words, is it the shock absorber-like cartilage disc getting squished between our spine’s vertebrae or the crumbling spinal tower theory that can explain why we seem to be shrinking in height after retirement.
Subjects in this study were selected from a 232 Finnish identical twins initially recruited in a Twin Spine Study in the late 50’s. Twin populations are particularly interesting, as they tend to tell us a lot about human similarities and differences in the context of aging and genetics. Apparently, this group of men was also highly representative of the average Finnish population and thus an applicable sample population of the typical European descendant’s spine. These selected gents were at an average age of 63 years (ranging between 50 and 79) at the time of the final follow-up, thus putting them at in their late 40’s/early 50’s on the initial measures. Videman’s team took particular interest in the low back or lumbar spine, focusing in on the MRI’s over the years. They tried to precisely measure the consistent changes in structure and form of the discs and vertebrae during five, 10, and 15-year follow-up studies.
The disc height comparisons concluded that we are indeed getting shorter gradually with a flattening of the disc at five years out by approximately three per cent. The 15-year follow-up found a continued slow compression by 8 per cent in the upper discs to 11 per cent in lower discs of the low back. Measurements of the low back’s bony vertebra at five years out could not find signs of any height changes. However, looking at the 15-year follow-up MRI’s, they found significant vertebra height growth by an average of three per cent in the upper vertebrae levels and by five per cent in the lower back vertebrae after 15 years. Thus, our discs do flatten slowly, but the spinal vertebrae keep pace in remodeling or growing taller (as well as wider) with age. Looking more closely at what exactly happens to the disc and vertebrae at their interface, this article found that the once clearly defined junction appeared to have more or less “melted” into one another. This merging of bone and cartilage results in the appearance of taller spinal vertebra and a narrowed or flattened disc. We are getting shorter, but by only .13 millimeters per year on an annual average after middle age. This not-so-incredibly shrinking average man was in line with the average decrease in our standing height by three millimeters from their baseline measured height to their re-measured height at the 15-year follow-up.
It can be confirmed that we gradually lose somewhere between 9 to 13 per cent of our lumbar disc height in a 15-year period around middle-aged, but why? Videman’s team found a lot of variations within the sample population of researched subjects. Some subjects had no measurable loss of disc height, whereas others had significant disc height flattening, due to degeneration. The exact process of degenerating discs and additional vertebral bone growth is speculated in this paper based on other spine-related research. Two proposed explanations include a cumulative micro-trauma theory at the disc-vertebra interface that creates an inflammation process and merging of the cartilage and bone. The second theory suggests a gradual tensioning of the disc pulling on the vertebra that eventually triggers a process of converting the cartilage to bone. Either way, this was a strong paper with a fairly large population size, precise MRI measurements and a 15 years of follow-up research. There was good evidence in this paper that we are losing disc height and gaining vertebral height at a nearly equal rate. Further research was suggested to explore the exact mechanism causing gain in vertebral height.