From the Guidelines
Intervertebral disc degeneration is primarily caused by a combination of aging, wear and tear, and lifestyle factors, with the natural aging process being a significant contributor, as evidenced by a systematic review of 33 articles showing an increasing prevalence of degenerative spine findings in asymptomatic patients of increasing age 1. The main reasons for intervertebral disc degeneration include:
- Natural aging process: As people get older, discs lose water content and become less flexible, with a prospective study by Carragee et al showing that among patients with lumbar imaging abnormalities before the onset of LBP, 84% had unchanged or improved findings after symptoms developed 1.
- Repetitive stress: Daily activities and movements put pressure on the discs over time, with a prospective cohort study of 20 patients showing no significant differences in MRI changes over 12 months in patients presenting with acute LBP compared with their asymptomatic counterparts, except in disc herniation, nerve root compression, and annular fissure 1.
- Injuries: Trauma to the spine can accelerate degeneration, although even in the setting of disc herniation, imaging may have limited role in management as the majority of disc herniations show some degree of reabsorption or regression by 8 weeks after symptom onset 1.
- Genetics: Some people may be more prone to disc degeneration due to their genetic makeup, with a systematic review of 33 articles finding an increasing prevalence of degenerative spine findings in asymptomatic patients of increasing age 1.
- Poor posture: Prolonged poor posture can lead to uneven pressure on discs, although the evidence for this is not as strong as for other factors 1.
- Lack of exercise: Weak core muscles provide less support for the spine, with a retrospective cohort study of 145,320 patients showing that non-adherence to guidelines leading to increased health care utilization 1.
- Smoking: Reduces blood supply to discs, impeding nutrition and repair, although this is not directly addressed in the provided evidence 1.
- Obesity: Excess weight puts additional stress on spinal discs, with a prospective population-based cohort study of 1,770 patients showing that increased health care utilization with early imaging has also been demonstrated in non-worker populations 1. To slow disc degeneration, it is recommended to maintain a healthy weight, exercise regularly to strengthen core muscles, practice good posture, avoid smoking, and use proper lifting techniques, although the evidence for these specific measures is not directly addressed in the provided study 1.
From the Research
Causes of Intervertebral Disc Degeneration
The causes of intervertebral disc degeneration are multifaceted and can be attributed to various factors, including:
- Genetic factors 2, 3
- Aging 2, 4, 3, 5
- Mechanical injury 2, 4
- Malnutrition 2
- Abnormal mechanical stress 5
- Smoking exposure 3
- Anthropometric factors, such as body weight and muscle strength 3
Pathological Changes
The pathological changes associated with intervertebral disc degeneration include:
- Senescence and apoptosis of nucleus pulposus cells (NPCs) 2, 5
- Progressive degeneration of extracellular matrix (ECM) 2, 5
- Fibrosis of annulus fibrosus (AF) 2
- Inflammatory response 2, 6
Role of Environmental Factors
Environmental factors, such as occupational exposures and whole-body vibration, have been found to have a limited effect on disc degeneration 3. However, routine loading may actually have some benefits to the disc 3.
Mechanisms of Nervous System Response
The nervous system response to disc degeneration involves the stimulation of nociceptors in the anulus fibrosus, causing nociceptive pain 6. This can lead to peripheral sensitization, where normally innocuous stimuli may generate an amplified response 6. Disc degeneration can also influence other spinal structures, such as facet joints, ligaments, and muscles, which can become pain generators 6.