Diurnal Variations of Lumbar Discs and the Varying Contributing Factors
Sitting and Sleeping
Discs are always either filling or emptying with water. Intervertebral discs are the large hydraulic structures between vertebrae that separate them in the spine. They undergo significant compression forces while we are upright, walking and sitting, and decompress when lying down. And this change is also known as the diurnal change.
However, the ‘diurnal’ term is a little misleading as it reflects a day-night cycle of change. In actual effect, the discs do not receive any light/dark cues as the changes are related to load exclusively, not by the sun’s position. Obviously, most mammals sleep at night and also lie down so the effects of less weight on the spine is the major factor at play.
In this interesting study1 a group of researchers led by Chanyuan Liu used 3T MRI (which has powerful resolution) to evaluate the disc’s water content of 71 females of the age range 19-31yrs to look at the changes of the discs across the day by taking readings in the morning and evening. They also considered lifestyle behaviours like how much time they spent in bed, daytime napping, activity, and sitting.
What did these researchers find?
Interestingly, those people with more daytime naps demonstrated by way of T2 mapping ( a technique to measure the water content in the discs) showed to increase their disc’s water content, while those that sat more lost water content. These changes were less noticeable in those people with a level of spine degeneration.
The researchers concluded:
The causative factors that affect the diurnal fluctuation of lumbar discs are lifestyle and weight. Disc hydration and microstructural stability reserves for upcoming daytime activities may be correlated with bed rest. Sitting may cause normal discs to become more dehydrated and degenerative discs to have less diurnal microstructural rearrangement. T2 mapping and DKI are effective methods for assessing disc biomechanics in clinical settings.
Dynamic Disc Designs
At ddd, we create models demonstrating disc dynamics to educate the patients on the biomechanical principles of the spine. In the study above, the diurnal changes that occur in human spines can influence low back pain. Our models can help professionals make sense of a patient’s experience of pain as it can change over the course of the day. This often creates re-assurance and maps out strategies to improve. Explore.