Why You’re Taller in the Morning and Shorter At Night

September 19, 2021

Finger pointing at vertebral disc in the lumbar spine, the anatomical structure responsible for why you're taller in the morning and shorter at night.

A fascinating natural phenomenon occurs each night we go to sleep. We all get a little taller. And as the day goes on, we all get a little shorter. Even though what happens is complex, the explanation is relatively simple.

You probably don’t feel taller in the morning after waking from a good night’s sleep, but you’ve actually grown. The reason lies in the vertebral column, specifically in what is known as the nucleus pulposus, or the inner part of the vertebral disc. The discs in the spine are composed of a gelatin-like material that provides cushioning and protection to the spine. It’s your body’s shock absorber, and with the pounding your vertebrae take during the day with walking, running, bending, lifting, and sitting, it needs time to rest and rejuvenate.

Human vertebrae anatomy diagram.

During the night, when there is no load placed on your spine, fluid is slowly diffusing into the discs in a passive process called imbibition. Without forces compressing the spine, which includes gravity when you’re standing or sitting, discs grow in size due to osmotic pressures. An analogy to consider is that of a balloon with extremely tiny holes in it that is filled with gelatin and water sitting in a tub of water. When the balloon is compressed, water seeps out, decreasing the volume in the balloon. When the compression is released, the reverse happens. Each disc goes through this process at rest and increases in height by a small amount.

The vertebral column is made up of 24 vertebrae (7 cervical vertebrae, 12 thoracic vertebrae, and 5 lumbar vertebrae), and between each vertebra is a disc, 23 in all. The height of the spine increases when you add up the amount that each disc increases in size at night. This makes you about one and a half to two centimeters (around 0.5 to 0.75 inches) taller in the morning. As the day progresses, the discs slowly lose some of their height due to compressive forces, and you’re back to being shorter at night again. The discs can be reduced by up to 15% from compressive forces that happen during the day.

While we get shorter at night and taller in the morning every day, we do shrink over the span of our lives. You weren’t just imagining things when someone you knew who was much older appeared shorter and shorter as they aged. The reason for this is the water content of the discs typically decreases with age. This results in a much narrower disc that doesn’t have the ability to “refill” fully. As before, when you add this up across the entire vertebral column, the loss of height becomes significant. Add to this the natural changes in the curves of the spine as we age, and the change in height becomes even more significant.

Spinal diseases of the spine diagram showing disc protrusion, herniated disc, degenerative disc, and osteophytes.

There are other types of disc problems that can also affect changes in height or give an idea of the health of the discs. One of the common questions asked for someone with back problems is if they have pain or stiffness in the morning after waking. Since the disc is at its fullest point during this part of the day, this can help test the indication of a bulging or herniated disc. Often the pain subsides as the day goes on since the pressure in the disc is decreased and the protrusion of the disc on the nerves in the spine is also reduced.

Even if there isn’t a problem present, many people are just stiff in the morning. Again this is because the disc is at its fullest pressure, and as you begin to move and compress those discs, the stiffness decreases. Of course, there can be other things in play and in the mix, such as ligament, muscle, or soft tissue tightness of the back and neck. A degenerated disc or a thinning disc can also cause problems in the spine and with how well the disc fills at night.

So why do the discs go through this every night, you may ask? The diffusion of fluid provides nutrients to the nucleus pulposus, the central part of the disc, and the fibrous rings that surround it to keep the material in place called the annulus fibrosus. A lack of motion and physical activity decreases disc nutrition, but too much overload on the disc can also lead to those other disc problems mentioned before.

So there is a fine line to walk with disc health. Modern stressors contribute significantly to problems of the discs in the back. Excessive sitting, low amounts of physical activity, and poor posture all reduce the health of the discs. Loading of the spine and movement allows unloading later on and the ability for the discs to revitalize themselves. So keep moving to make sure you keep growing by the time the sun comes up in the morning.

I’m the editor and writer of Knowledge Stew, but also a licensed Physical Therapist that has been treating all types of back conditions for the past 18 years.

About the author 

Daniel Ganninger - The writer, editor, and chief lackey of Knowledge Stew, the author of the Knowledge Stew line of great trivia books, and editor of Fact World and the Knowledge Stew sister site on Medium. I hope you find things here to annoy those around you with your new found knowledge.

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  • Is any of the daily height change due to the replenishment of the synovial fluids in the joints?

    I ask this question with particular emphasis on the knee joint,

    • Thanks for the question, Harry.
      Specifically in the spine, the change in height is pretty much attributed to the disc volume and height (with bony changes being the other). While you do have synovial fluid in the joints of the spine, specifically the facet joints, they don’t change in volume. It is held constant in the joint capsule and is replenished as you said but doesn’t change. The same goes for the knee. The joint capsule of the knee, and the synovial fluid in it, don’t change in a healthy state. Changes due to osteoarthritis or some other musclo-skeletal dysfunction, however, cause the viscosity of the synovial fluid in these joints to become less viscous (and decrease in volume) as well as a decrease in intracapsular pressure (pressure in the joint capsule). But this doesn’t significantly affect height like the discs in the spine. On a side note, the joints and synovial fluid like passive motion (pump) while the discs prefer loading and unloading. Great question!

    • Good question. There really isn’t any way not to lose height during the day other than staying in bed (which of course isn’t recommended). Since the compression that occurs in the discs across the vertebral column is due to gravity and compressive forces through weight-bearing activities, there is no way to counteract this. But that is okay since the discs revitalize themselves at night when you’re laying down. Good posture, however, will benefit height as you age, as the discs will lose less volume which decreases with age. Good posture encourages better revitalization of the discs at rest and the spine is able to handle compressive forces better during the day. Dowager’s hump is a good example of posture that has gone bad. Thanks for the question.

  • On average, people lose about 3/4 of an inch during the day. However, you can lose a solid inch, or even a tad more, from excessive twisting, dehydration and overloading the spine. I have noticed this from my own height, and from others who do regular measurements.

    • Good question. The only thing I could think of would be sleeping somewhat upright like in a reclining chair. This is something that you’ll hear back pain sufferers doing as it decreases the pain for some during sleep as sleeping supine (on the back) causes them discomfort. This makes sense since the filling of the discs I believe would be decreased leading to a reduction on whatever dysfunction they had in the back. But it’s obviously not the optimal way to sleep nor does it give the chance for the discs to revitalize themselves. It’s a catch-22 type of situation for people in these situations.

      • last question Daniel.
        I had a foot injury when i was 18 (have five screws inside). Does it have affect on daily shrinkage of height. I feel that my foot is strong at 26 years old.

        • Sorry Pete, I missed your question. Only almost a month late. But to answer it better late than never, that type of surgical repair shouldn’t have any change on your height at least in a daily since. Joints of the knees, hips, and ankles don’t change in height like changes in the spine. I don’t know of any appreciable height change that occurs in any other joints of the body other than the spine.

  • I only go down by 1.2 to 1.3cm throughout the day, and 1.6cm on a challenging day. I thought average daily height loss throughout the day was closer to half an inch in reality? Two centimetres seems quite extensive, that’s almost a full inch lost.

    • I’m a practicing Physical Therapist and this is what I’ve learned through the years through schooling and continuing education. I’ve also treated hundreds and hundreds of back patients. It’s one of the few articles I didn’t include references because of that.

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