Why do we get shorter as we age? First of all, I want to make it clear, I am talking about your height, or how tall. I am Dr. John Shim and I hope you have already had the opportunity to review my video’s about basic spine anatomy and why disc’s degenerate. Understanding those concepts are helpful to understanding the explanation the common question of “why do we get shorter as we age?”. Besides the spine, there are other reasons why we get shorter, but we will concentrate strictly on the spine. In the Disc degeneration video, the concept of disc dehydration, and the resultant narrowing of the disc space was presented. As the animation will demonstrate, the once tall, normal sized disc of our youth will give way to a dehydrated, bulging and narrowing disc. The disc height can reduce significantly. The vertebral body sandwich, or functional spine unit is composed of the vertebral bodies alternating with the intervertebral disc. There are some population differences, but most collected anatomy data indicate a normal disc height for men averages about 11 mm, and women 9 mm. Population studies have definitely demonstrated a narrowing, and degeneration of the discs with age. Interestingly, not every disc in every person will narrow. But in General, the disc narrowing will occur in almost every person. The current conventional wisdom is that after age 40, we shrink an average of ¼ to 1/3 of an inch every decade. In addition to the disc decrease, there is another effect secondary to the change of the shape of the disk, and the functional spine unit. When young, the spine has a natural three smooth visible curves orientation. The neck, or cervical spine gently curves backward. The upper back, or thoracic spine curves forwards. The lower back or lumbar spine curves backwards. The backward curves are called lordosis. The forward curve is called kyphosis. In the normal situation, the head is balanced over the pelvis, and this allows the most efficient use of body energy to maintain property body mechanics and orientation. As the discs degenerate and narrow, it causes the the lordotic curves to straighten, and the kyphosis to become more curved. As a result, to keep the head positioned over the pelvis, often times, the knees and hips need to be slightly bent to maintain the proper position, and balance. This change of posture also results in the “shortening or shrinking of the height”. Osteoporosis can also be a significant contributing factor to shortening. The bones collapse, causing loss of height, and also causes more kyphosis. As discussed before, the body must compensate for this kyphosis by again bending at the hips and knees. As you now understand, the disc degeneration process leads to shrinkage or shortening by both a reduction in height, and a change of the posture to achieve a balanced position. Osteoporosis can also make a significant impact on the height. There are other factors that contribute to shrinkage like loss of cartilage height in our hips, and knees, or falling of our arches in our feet. But as a spine surgeon and specialist, I can say the most significant factor causing age related shrinkage is your spine. I hope you have a better understanding of this process. This is Dr. John Shim. Thanks you for your attention.
Tell me how tall you are. If you are have not been measured in a few years, my bet is that you are shorter than you think you are and most likely shorter than you were 10 years ago. Due to the aging of bones, joints, muscles and discs, we are getting a little shorter every day.
Estimates vary on where you look, but on average people lose ¼ to ½ inch every decade after age 40 or 50, with losses increasing in later years, and women generally losing more than men. Research from the Baltimore Longitudinal Study of Aging, for example, found that women lost an average of 2 inches between the ages of 30 and 70 (and just over 3 inches by age 80). Men lost a little more than 1 inch by age 70 (and 2 inches by 80). There is a wide variability: Some people lose an inch or more in a single decade, some shrink only after age 60 or 70, and a few don’t shrink at all.
One of the biggest reasons for shrinking as we get older is our spine. The discs, which start out with a high percentage of fluid in them, as they work as a shock absorber in the body, gradually lose that fluid. This dehydration gradually narrows each affected disc space and shorten the spine. If there is a history of disc herniation, this dehydration can happen at an earlier age and much faster.
Osteoporosis is also a culprit. With the loss of bone height and density, the possibility of fractures increases, especially in women. In turn, a fracture will again reduce the height of the vertebral body.
Between disc space narrowing and osteoporosis, there is often a loss of the normal curves of the spine. The body, wanting to correct itself, changes its normal posture to bend the knee and hips to keep the head in line with the feet, .and again there is a loss of height.
Preventing this completely is almost impossible, but there are things we can do to slow the process down. Look after your back. Get a bone density. Take calcium and vitamin D, and do weight bearing exercises early and throughout your life. Some of us cannot afford to lose an inch, let alone three.
- Paholpak P, Dedeogullari E, Lee C, Tamai K, Barkoh K, Sessumpun K, Wang JC, Buser Z. Do modic changes, disc degeneration, translation and angular motion affect facet osteoarthritis of the lumbar spine. Eur J Radiol. 2018 Jan;98:193-199. PubMed PMID: 29279162