Hypertension is Independently Associated with Lumbar Disc Degeneration: A Large-Scale Population-Based Study
Authors: Samartzis D. , Bow C. , Karppinen J. , Luk K. D. K. , Cheung B. M. Y. , Cheung K. M. C. 
Published: May 2014

Introduction Low back pain (LBP) is the most disabling condition in the world. Lumbar intervertebral disc degeneration is one of the risk factors for LBP. In particular, specific clinically relevant phenotypes of degeneration, such as moderate and severe degenerative changes, have been noted to increase the risk of the development of low back pain. Although progressive age, abnormal biomechanics, and genetics play a role in the development of disc degeneration, cardiovascular risk factors (e.g., age, smoking, obesity, etc.) have also been suggested to be determinants. Hypertension, manifesting as elevated systolic and/or diastolic blood pressure, is a factor related to cardiovascular disease; however, its role in the development of disc degeneration among a population remains speculative. As such, this large-scale population-based study addressed the association of blood pressure in relation to lumbar disc degeneration. Materials and Methods This was a cross-sectional study of the Hong Kong Disc Degeneration-Cardiovascular Cohort, currently composed of approximately 1,800 Southern Chinese volunteers. At the time of analyses, there were 1,261 subjects (36.6 males; 63.4% females) with a mean age of 52.4 years (range: 30-89; SD: ± 6.3 years). Serum lipid profile, glucose, ESR, and other blood parameters were assessed. Anthropomorphic and lifestyle/environmental (e.g., smoking, exercise, occupation) measurements as well as pain profiles were obtained of all subjects. Systolic and diastolic blood pressure assessment was conducted on three occasions. Hypertension was defined as systolic blood pressure of ≥ 140 mm Hg and/or diastolic pressure of ≥ 90 mm Hg. Medication use was accounted. Each subject had undergone T2-weighted MRI of the lumbar spine from L1-S1. Disc degeneration of each lumbar disc was assessed by the Schneiderman et al radiographic criteria. A summated degenerative disc disease (DDD) score was obtained of the entire lumbar spine. DDD score was used to denote subjects with normal, mild, medium, moderate, and severe degrees of disc degeneration. A DDD score of 5 of greater was regarded as a moderate/severe imaging phenotype of disc degeneration. Additional spinal imaging phenotypes (e.g., Modic changes, Schmorl nodes, etc.) were also assessed. Results Overall disc degeneration was present in 79% of all the subjects, most prevalent at L4-L5 (57.9%). Mean DDD score was 3.4 (range: 0-14; SD: ± 2.9 score). Mean systolic and diastolic measurements were 127.0 (range: 81-225; SD: ± 20.1 mm Hg) and 75.6 (range: 41-120; SD: ± 12.3 mm Hg), respectively. Mean systolic/diastolic values were significantly elevated in individuals with the overall presence of disc degeneration (mean: 127.6/76.0 mm Hg) compared with subjects with normal discs (mean: 124.3/73.9 mm Hg) ( p < 0.001). Mean systolic/diastolic values were also significantly greater in individuals with moderate/severe disc degeneration (mean: 131.1/77.6 mm Hg) compared with those that had less severe grades of degeneration (mean: 125.1/74.62 mm Hg) ( p < 0.001). Among the 1,261 subjects, 28% had hypertension. Hypertension was noted in 35.5% of those with moderate/severe disc degeneration compared with 24.5% with less severe degenerative profiles ( p < 0.001). Based on a multivariate regression model adjusting for age, Modic changes, Schmorl nodes, diabetes, ESR, and LBP status, hypertension was significantly related to moderate/severe disc degeneration (OR: 1.51; 95% CI: 1.05-2.17; p = 0.027). Conclusion Based on one of the largest population-based studies addressing imaging, environmental/lifestyle, and cardiovascular risk factors, this study has illustrated for the first time that elevated blood pressure is “independently” associated with different stages of lumbar disc degeneration on MRI. Hypertension increases the likelihood of moderate/severe disc degeneration, a phenotype highly associated with LBP, by 50%. In an age where people are becoming less physically active and more overweight/obese, the prevalence of cardiovascular risk factors will continue to increase. As such, this study raises further awareness of the potential role of vascular disease in a “predictive risk profile model” of lumbar disc degeneration. Disclosure of Interest None declared