Lumbar disc degeneration: correlation with age, sex, and spine level in 600 autopsy specimens.
TL;DR: Using data from 16 published reports, the authors correlated macroscopic disc degeneration grades with age, sex, and spine level in 600 lumbar Intervertebral discs from 273 cadavers and suggest that higher mechanical stress, perhaps combined with longer nutritional pathways, may be responsible for the earlier degeneration of male discs.
Abstract: Using data from 16 published reports, the authors correlated macroscopic disc degeneration grades with age, sex, and spine level in 600 lumbar intervertebral discs from 273 cadavers (ages: 0-96 years). Male discs were more degenerated than female discs at most ages; significantly so in the second, fifth, sixth, and seventh decades. On average, L4-L5 and L3-L4 level discs showed more degeneration than discs at other lumbar levels. These macroscopic findings corroborate radiographic data from epidemiologic studies. The calculations suggest that higher mechanical stress, perhaps combined with longer nutritional pathways, may be responsible for the earlier degeneration of male discs.
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TL;DR: The results suggest that BMI is age and sex dependent when used as an indicator of body fatness, but that it is ethnicity independent in black and white adults.
Abstract: This study tested the hypothesis that body mass index (BMI) is representative of body fatness independent of age, sex, and ethnicity. Between 1986 and 1992, the authors studied a total of 202 black and 504 white men and women who resided in or near New York City, were ages 20-94 years, and had BMIs of 18-35 kg/m2. Total body fat, expressed as a percentage of body weight (BF%), was assessed using a four-compartment body composition model that does not rely on assumptions known to be age, sex, or ethnicity dependent. Statistically significant age dependencies were observed in the BF%-BMI relations in all four sex and ethnic groups (p values < 0.05-0.001) with older persons showing a higher BF% compared with younger persons with comparable BMIs. Statistically significant sex effects were also observed in BF%-BMI relations within each ethnic group (p values < 0.001) after controlling first for age. For an equivalent BMI, women have significantly greater amounts of total body fat than do men throughout the entire adult life span. Ethnicity did not significantly influence the BF%-BMI relation after controlling first for age and sex even though both black women and men had longer appendicular bone lengths relative to stature (p values < 0.001 and 0.02, respectively) compared with white women and men. Body mass index alone accounted for 25% of between-individual differences in body fat percentage for the 706 total subjects; adding age and sex as independent variables to the regression model increased the variance (r2) to 67%. These results suggest that BMI is age and sex dependent when used as an indicator of body fatness, but that it is ethnicity independent in black and white adults.
1,490 citations
Cites background from "Lumbar disc degeneration: correlati..."
...Due to kyphosis and osteoporotic degeneration of vertebral bodies, older subjects reportedly have a higher proportion of stature contributed by the lower extremities and pelvis than do young subjects (24-27)....
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...The linear dimensions of appendicular bones such as the tibia do not change with aging as do vertebrae (24-27)....
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TL;DR: The intervertebral disc is a cartilaginous structure that resembles articular cartilage in its biochemistry, but morphologically it is clearly different, and shows degenerative and ageing changes earlier than does any other connective tissue in the body.
Abstract: The intervertebral disc is a cartilaginous structure that resembles articular cartilage in its biochemistry, but morphologically it is clearly different. It shows degenerative and ageing changes earlier than does any other connective tissue in the body. It is believed to be important clinically because there is an association of disc degeneration with back pain. Current treatments are predominantly conservative or, less commonly, surgical; in many cases there is no clear diagnosis and therapy is considered inadequate. New developments, such as genetic and biological approaches, may allow better diagnosis and treatments in the future.
1,124 citations
Additional excerpts
...severely degenerate [6]....
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TL;DR: The degenerative disc, having lost its height, effects the structures close by, such as ligamentum flavum, facet joints, and the shape of the neural foramina, the main cause of spinal stenosis and radicular pain due to the disc degeneration in the aged populations.
Abstract: This review article describes anatomy, physiology, pathophysiology and treatment of intervertebral disc. The intervertebral discs lie between the vertebral bodies, linking them together. The components of the disc are nucleus pulposus, annulus fibrosus and cartilagenous end-plates. The blood supply to the disc is only to the cartilagenous end-plates. The nerve supply is basically through the sinovertebral nerve. Biochemically, the important constituents of the disc are collagen fibers, elastin fibers and aggrecan. As the disc ages, degeneration occurs, osmotic pressure is lost in the nucleus, dehydration occurs, and the disc loses its height. During these changes, nociceptive nuclear material tracks and leaks through the outer rim of the annulus. This is the main source of discogenic pain. While this is occurring, the degenerative disc, having lost its height, effects the structures close by, such as ligamentum flavum, facet joints, and the shape of the neural foramina. This is the main cause of spinal stenosis and radicular pain due to the disc degeneration in the aged populations. Diagnosis is done by a strict protocol and treatment options are described in this review. The rationale for new therapies are to substitute the biochemical constituents, or augment nucleus pulposus or regenerate cartilaginous end-plate or finally artificial disc implantation..
569 citations
Cites background from "Lumbar disc degeneration: correlati..."
...About 20% of people in their teens have discs with mild signs of degeneration; degeneration increases steeply with age, particularly in males, so that around 10% of 50-year-old discs and 60% of 70-year-old discs are severely degenerate.(5)...
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TL;DR: The capability of the most commonly used methods to assess total adiposity and fat distribution is summarized, and it has been shown that in particular the visceral fat depot is associated with metabolic disease risk.
Abstract: Numerous techniques are available to estimate body composition and fat distribution, and the method to use will depend on the aim of the study, economic resources, availability, time, and sample size. 6–8 Multi-compartment models, such as underwater weighing, dilution techniques and dual-energy X-ray absorptiometry (DXA) are all reliable methods to obtain accurate measures of total body fat. However, because of their costs in terms of time andmoney, thesemethods are not practical in large epidemiological studies and for routine clinical use. In these situations, body mass index (BMI) is often used and assumed to represent the degree of body fat. BMI, however, does not distinguish between fat mass and lean (non-fat) mass. For example, well-trained body builders have a very low percentage of body fat, but their BMI may be in the overweight range because of their large lean (muscle) mass. In addition, in the elderly and non-Caucasian populations, the relationship between BMI and body fatness may be different as compared with younger Caucasian populations. 9–14 Another potential limitation of the BMI is that the distribution of fat over the body is not captured. Many studies have shown that an abdominal fat distribution, independent of overall obesity, is associated with metabolic disturbances and increased disease risk. 15–23 An increased abdominal fat accumulation is largely caused by the accumulation of visceral (or intraabdominal) fat (for distinction of these fat depots, see Figure 1). Owing tometabolic differences between different fat depots, they differ in their role of predicting metabolic disturbances and diseases. Table 1 summarizes the capability of the most commonly used methods to assess total adiposity and fat distribution. Abdominal obesity is usually assessed by the easily measured waist circumference, the waist-to-hip circumference ratio (WHR), or the less-commonly used sagittal abdominal diameter (SAD). By the use of sophisticated imaging techniques, such as magnetic resonance imaging (MRI) and computed tomography (CT), different fat depots can be distinguished at the waist level, and it has been shown that in particular the visceral fat depot is associated with metabolic disease risk. 24–30 Because the SAD or waist circumference alone are more strongly correlated with visceral fat than the WHR, 31–35 guidelines tend to focus onwaist circumference to estimate disease risk as suggested by Lean et al. 36 These widely used cut-points (i.e. 102 cm formen and 88 cm for women) were originally based on a replacement of the classification of BMI, 36 but other cut-points have also been suggested on the basis of relationships with visceral fat area. 37
540 citations
TL;DR: Examination of individual features revealed that disc height and bulge were highly heritable at both sites, and osteophytes were heritable in the lumbar spine, suggesting an important genetic influence on variation in intervertebral disc degeneration.
Abstract: Objective
Degenerative intervertebral disc disease is common; however, the importance of genetic factors is unknown. This study sought to determine the extent of genetic influences on disc degeneration by classic twin study methods using magnetic resonance imaging (MRI).
Methods
We compared MRI features of degenerative disc disease in the cervical and lumbar spine of 172 monozygotic and 154 dizygotic twins (mean age 51.7 and 54.4, respectively) who were unselected for back pain or disc disease. An overall score for disc degeneration was calculated as the sum of the grades for disc height, bulge, osteophytosis, and signal intensity at each level. A “severe disease” score (excluding minor grades) and an “extent of disease” score (number of levels affected) were also calculated.
Results
For the overall score, heritability was 74% (95% confidence interval [95% CI] 64–81%) at the lumbar spine and 73% (95% CI 64–80%) at the cervical spine. For “severe disease,” heritability was 64% and 79% at the lumbar and cervical spine, respectively, and for “extent of disease,” heritability was 63% and 63%, respectively. These results were adjusted for age, weight, height, smoking, occupational manual work, and exercise. Examination of individual features revealed that disc height and bulge were highly heritable at both sites, and osteophytes were heritable in the lumbar spine.
Conclusion
These results suggest an important genetic influence on variation in intervertebral disc degeneration. However, variation in disc signal is largely influenced by environmental factors shared by twins. The use of MRI scans to determine the phenotype in family and population studies should allow a better understanding of disease mechanisms and the identification of the genes involved.
505 citations