Smoking and intervertebral disc degeneration

Causal associations between modifiable risk factors and intervertebral disc degeneration

BACKGROUND

Intervertebral disc degeneration (IVDD) is a common degenerative condition, which is thought to be a major cause of lower back pain (LBP). However, the etiology and pathophysiology of IVDD are not yet completely clear.

PURPOSE

To examine potential causal effects of modifiable risk factors on IVDD.

STUDY DESIGN

Bidirectional Mendelian randomization (MR) study.

PATIENT SAMPLE

Genome-wide association studies (GWAS) with sample sizes between 54,358 and 766,345 participants.

OUTCOME MEASURES

Outcomes included (1) modifiable risk factors associated with IVDD use in the forward MR; and (2) modifiable risk factors that were determined to have a causal association with IVDD in the reverse MR, including smoking, alcohol intake, standing height, education level, household income, sleeplessness, hypertension, hip osteoarthritis, HDL, triglycerides, apolipoprotein A-I, type 2 diabetes, fasting glucose, HbA1c, BMI and obesity trait.

METHODS

We obtained genetic variants associated with 33 exposure factors from genome-wide association studies. Summary statistics for IVDD were obtained from the FinnGen consortium. The risk factors of IVDD were analyzed by inverse variance weighting method, MR-Egger method, weighted median method, MR-PRESSO method and multivariate MR Method. Reverse Mendelian randomization analysis was performed on risk factors found to be caustically associated with IVDD in the forward Mendelian randomization analysis. The heterogeneity of instrumental variables was quantified using Cochran's Q statistic.

RESULTS

Genetic predisposition to smoking (OR=1.221, 95% CI: 1.068-1.396), alcohol intake (OR=1.208, 95% CI: 1.056-1.328) and standing height (OR=1.149, 95% CI: 1.072-1.231) were associated with increased risk of IVDD. In addition, education level (OR=0.573, 95%CI: 0.502-0.654)and household income (OR=0.614, 95%CI: 0.445-0.847) had a protective effect on IVDD. Sleeplessness (OR=1.799, 95%CI: 1.162-2.783), hypertension (OR=2.113, 95%CI: 1.132-3.944) and type 2 diabetes (OR=1.069, 95%CI: 1.024-1.115) are three important risk factors causally associated with the IVDD. In addition, we demonstrated that increased levels of triglycerides (OR=1.080, 95%CI:1.013-1.151), fasting glucose (OR=1.189, 95%CI:1.007-1.405), and HbA1c (OR=1.308, 95%CI:1.017-1.683) could significantly increase the odds of IVDD. Hip osteoarthritis, HDL, apolipoprotein A-I, BMI and obesity trait factors showed bidirectional causal associations with IVDD, therefore we considered the causal associations between these risk factors and IVDD to be uncertain.

CONCLUSIONS

This MR study provides evidence of complex causal associations between modifiable risk factors and IVDD. It is noteworthy that metabolic disturbances appear to have a more significant effect on IVDD than biomechanical alterations, as individuals with type 2 diabetes, elevated triglycerides, fasting glucose, and elevated HbA1c are at higher risk for IVDD, and the causal association of obesity-related characteristics with IVDD incidence is unclear. These findings provide new insights into potential therapeutic and prevention strategies. Further research is needed to clarify the mechanisms of these risk factors on IVDD.

Hydroquinone, an Environmental Pollutant, Affects Cartilage Homeostasis through the Activation of the Aryl Hydrocarbon Receptor Pathway

Exposure to environmental pollutants has a proven detrimental impact on different aspects of human health. Increasing evidence has linked pollution to the degeneration of tissues in the joints, although through vastly uncharacterised mechanisms. We have previously shown that exposure to hydroquinone (HQ), a benzene metabolite that can be found in motor fuels and cigarette smoke, exacerbates synovial hypertrophy and oxidative stress in the synovium. To further understand the impact of the pollutant on joint health, here we investigated the effect of HQ on the articular cartilage. HQ exposure aggravated cartilage damage in rats in which inflammatory arthritis was induced by injection of Collagen type II. Cell viability, cell phenotypic changes and oxidative stress were quantified in primary bovine articular chondrocytes exposed to HQ in the presence or absence of IL-1β. HQ stimulation downregulated phenotypic markers genes SOX-9 and Col2a1, whereas it upregulated the expression of the catabolic enzymes MMP-3 and ADAMTS5 at the mRNA level. HQ also reduced proteoglycan content and promoted oxidative stress alone and in synergy with IL-1β. Finally, we showed that HQ-degenerative effects were mediated by the activation of the Aryl Hydrocarbon Receptor. Together, our findings describe the harmful effects of HQ on articular cartilage health, providing novel evidence surrounding the toxic mechanisms of environmental pollutants underlying the onset of articular diseases.

Bacteria in human lumbar discs - subclinical infection or contamination? Metabolomic evidence for colonization, multiplication, and cell-cell cross-talk of bacteria

BACKGROUND CONTEXT

The accumulating evidence associating sub-clinical infection with disc degeneration (DD) and the controversy of contamination versus infection mandates a further understanding of the microbial activity in the disc and host-microbiome interaction.

PURPOSE

To utilize a novel approach of metabolomics to probe the presence of bacterial metabolites involved in colonization, survival, and replication in human lumbar intervertebral discs (LIVD).

STUDY DESIGN

An observational case-control study.

PATIENT SAMPLE

Nucleus pulposus from the LIVD of three brain-dead voluntary organ donors (MRI normal and classified as controls) and of three patients undergoing surgery for disc degeneration (DD) (cases) were utilized.

METHODS

Untargeted metabolite profiling was carried out in six discs (3-controls and 3-cases) after extraction using methanol: acetonitrile: water (2:2:1) solvent system and acquired through HPLC-MS/MS platform using C18 reversed-phase column. From the total IVD metabolome, microbial metabolites were filtered by mapping against HMDB, ChEBI, SigMol, Siderophore database, ecdmb database, and PaMet databases. The biological functions of the metabolites were then studied by MSEA pipeline from Metaboanalyst, and the enrichment ratio, p-value, and Variably Importance Projection scores of the metabolites were calculated. Degeneration responsive changes in the abundance of the microbial metabolites were calculated based on the peak intensities between the control and cases.

RESULTS

Mass spectrometry identified a total of 17601 and 15003 metabolites, respectively, in the control and degenerated discs. Preliminary mapping of the above metabolites against HMDB indicated the multiple sources, and of these, 64 metabolites were of microbial origin, accounting for 1.6% of the total IVD metabolome. Principle Component Analysis and Orthogonal Partial Least Square-Discriminant Analysis (OPLS-DA) showed distinct clustered patterns between control and disc degene`ration, indicating a strong variation in concentration, peak, and spectral values of the 64 metabolites between controls and cases. After the exclusion of metabolites that were also associated with humans, drugs, and food, 39 metabolites specific to bacteria were isolated. Nine were primary metabolites related to bacterial growth and survival, and the remaining 30 were secondary metabolites related to different environmental stress response activities. The three significant pathways (p<.001) which were predominant in the bacterial metabolites were autoinducer-2 biosynthesis, peptidoglycan biosynthesis, and chorismate pathway. In addition, a significant fold change of >1.0 was found for nine metabolites which included (S)-14-Methyilhexadecanoic acid related to P. acnes, 9-OxoODE, and 13-OxoODE related to gut flora, vibriobactin - a siderophore, tuberculosinol and iso-tuberculosinol, virulence factors of M. tuberculosis. There was also upregulation of Autoinducer- 2, an important "Quorum sensing molecule" involved in bacterial cross-talk.

CONCLUSION

We identified several bacterial-specific metabolites participating in bacterial growth, survival, and cross-talk pathways. These were found in both groups but up-regulated in degenerated discs. The presence of Quorum sensing molecules and cell-cell interactions provides firm proof of colonization and growth. These findings indicate that the bacterial presence may not be mere contamination but could be colonization with a possible role in infection-mediated inflammation in DD.

CLINICAL SIGNIFICANCE

Proof of subclinical infection as an initiator of DD and documentation of exact germ and drug sensitivity will change the way millions of patients with non-specific low back pain (NSLBP) are treated across the world.

Successful annuloplasty using the cone-beam computed tomography-assisted radiofrequency thermocoagulation system in a patient with severe vertebral deformity: a case report

Background

Complex anatomical features are challenging for minimally invasive intradiscal therapy owing to insufficient visualization for accurate needle advancement. We report the case of a patient with dysraphic vertebral pathologies who presented with L5/S1 degeneration and was successfully treated with annuloplasty using the cone-beam computed tomography (CBCT)-assisted radiofrequency thermocoagulation system.

Case presentation

A 34-year-old woman presented with a lower back and left radicular pain of L5/S1 discogenic origin, accompanied by spina bifida occulta and lumbosacral transitional vertebra. Radiofrequency annuloplasty was performed to preserve disc height and spinal stability, with real-time CBCT guidance for the congenital and degenerative conditions. The procedure relieved her left lower-extremity pain and magnetic resonance imaging revealed that the L5/S1 disc bulging decreased while the disc height was preserved.

Conclusion

Optimal accessibility of radiofrequency thermocoagulation and effective needle guidance using CBCT significantly improve the success rate of annuloplasty at the L5/S1 degenerative disc with severe vertebral deformity.

Development, Pathogenesis, and Regeneration of the Intervertebral Disc: Current and Future Insights Spanning Traditional to Omics Methods

The intervertebral disc (IVD) is the fibrocartilaginous joint located between each vertebral body that confers flexibility and weight bearing capabilities to the spine. The IVD plays an important role in absorbing shock and stress applied to the spine, which helps to protect not only the vertebral bones, but also the brain and the rest of the central nervous system. Degeneration of the IVD is correlated with back pain, which can be debilitating and severely affects quality of life. Indeed, back pain results in substantial socioeconomic losses and healthcare costs globally each year, with about 85% of the world population experiencing back pain at some point in their lifetimes. Currently, therapeutic strategies for treating IVD degeneration are limited, and as such, there is great interest in advancing treatments for back pain. Ideally, treatments for back pain would restore native structure and thereby function to the degenerated IVD. However, the complex developmental origin and tissue composition of the IVD along with the avascular nature of the mature disc makes regeneration of the IVD a uniquely challenging task. Investigators across the field of IVD research have been working to elucidate the mechanisms behind the formation of this multifaceted structure, which may identify new therapeutic targets and inform development of novel regenerative strategies. This review summarizes current knowledge base on IVD development, degeneration, and regenerative strategies taken from traditional genetic approaches and omics studies and discusses the future landscape of investigations in IVD research and advancement of clinical therapies.

Smoking and degenerative spinal disease: A systematic review

Smoking is a major cause of morbidity and mortality worldwide and is responsible for the death of more than 8 million people per year globally. Through a systematic literature review, we aim to review the harmful effects of tobacco smoking on degenerative spinal diseases (DSD). DSD is a debilitating disease and there is a need to identify if smoking can be an attributable contender for the occurrence of this disease, as it can open up avenues for therapeutic options. Sources such as PubMed and Embase were used to review literature, maintaining tobacco smoking and spinal diseases as inclusion factors, excluding any article that did not explore this relationship. Risk of bias was assessed using analysis of results, sample size and methods and limitations. Upon review of the literature, tobacco smoking was found to be a major risk factor for the occurrence of DSDs, particularly lumbar spinal diseases. Smokers also experienced a greater need for surgery and greater postoperative wound healing complications, increased pain perception, delay in recovery and decreased satisfaction after receiving surgery. These effects were noted along the entire spine. Many mechanisms of action have been identified in the literature that provide plausible pictures of how smoking leads to spinal degeneration, exploring possible primary targets which can open up opportunities to develop potential therapeutic agents. More studies on cervical and thoracic spinal degeneration would be beneficial in identifying the effect of nicotine on these spinal levels. Some limitations included insufficient sample size, inconclusive evidence and lack of sufficient repeat studies. However, there appears to be a sufficient amount of research on smoking directly contributing to lumbar spinal pathology.

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Smoking is a risk factor for the occurence of degenerative spinal disease (DSD).

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There are numerous pathological mechanisms attributed to spinal pathology by smoking.

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Smoking appears to be a significant risk factor for lumbar DSDs, with smoke studies also suggesting its role in cervical DSDs.

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There is insufficient research on the effect of smoking on the thoracic spine.

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Smoking leads to worse outcomes and potential complications post-surgery, as well as increased pain perception and poorer subjective response post-surgery.

Adverse impact of smoking on the spine and spinal surgery

Background

Tobacco smokers and companies are well aware that smoking increases the risks for cancers, vascular morbidity, and early mortality. This is a review of the plethora of adverse effects chronic smoking has on spinal tissues and spinal surgery.

Methods

Medline (PubMed) and Google Scholar databases were searched for pertinent literature through keywords related to smoking, spondylosis, and spinal surgery.

Results

Smoking accelerates spondylosis by impairing spinal tissue vascular supply through atherosclerosis and thrombosis, while inducing local hypoxia, inflammation, proteolysis, and cell loss. It, thus, compromises disc, cartilage, synovium, bone, and blood vessels. It can lead to early surgery, delayed wound healing, increased surgical site infection, failed fusion, more re-operations, and chronic spinal pain.

Conclusion

There is ample evidence to support surgeons' declining to operate on chronic smokers. The need for immediate and permanent smoking cessation and its potential benefits should be emphasized for the patient considering or who has undergone spinal surgery.

Pain intensity, e-cigarette dependence, and cessation-related outcomes: The moderating role of pain-related anxiety

Pain and nicotine dependence are prevalent, co-occurring conditions posited to interact in the manner of a positive feedback loop; however, most research to date has been conducted among tobacco cigarette smokers. Initial evidence suggests that pain is a risk factor for greater e-cigarette dependence, and additional research is needed to examine covariation between pain and e-cigarette use. There is reason to suspect that pain-related anxiety (i.e., the tendency to respond to pain with anxiety or fear) may be associated with greater e-cigarette dependence and difficulty quitting, and that pain intensity and pain-related anxiety may interact to confer greater risk for e-cigarette use. The current study represents the first examination of cross-sectional associations between pain intensity, pain-related anxiety, and e-cigarette dependence, motivation to quit, history of lifetime e-cigarette quit attempts, perceived barriers to cessation, and negative expectancies during abstinence from e-cigarettes. Participants (N = 520 e-cigarette users, 52.1% female, Mage = 34.85) completed an online survey assessing health behaviors. Results indicated that pain-related anxiety was positively associated with e-cigarette dependence and perceived barriers to cessation (ps < 0.05). Pain-related anxiety was found to moderate relations between pain intensity and primary outcomes, such that pain intensity was positively associated with motivation to quit, likelihood of past failed quit attempt, and negative abstinence expectancies among participants who endorsed high (but not moderate or low) levels of pain-related anxiety. Future research would benefit from examining prospective associations between pain-related anxiety, pain intensity, and e-cigarette use/cessation trajectories among individuals with chronic pain.

Population-based Risk Factors for the Development of Degenerative Disk Disease

STUDY DESIGN

This is a retrospective case control study.

OBJECTIVE

Identify risk factors and assess their relative impact on the development of degenerative disk disease (DDD).

SUMMARY OF BACKGROUND DATA

DDD is responsible for widespread disability in the civilian and military population. Despite the impact of low back pain and DDD, its multifactorial etiology is not entirely understood.

MATERIALS AND METHODS

The Defense Medical Surveillance System was searched for military members with the diagnosis of DDD as identified with the use of International Classification of Disease, 9th Revision (ICD-9) codes. These patients were compared with an age-matched and sex-matched control of military members without DDD from the Defense Medical Surveillance System. The prevalence of risk factors (obesity, hip, and knee osteoarthritis, tobacco dependence, diabetes, and type of employment) was then determined for both groups. In total, 160,911 patients with DDD were identified compared with 315,225 controls. Multivariate conditional logistical regression analysis was utilized to determine odds ratio (OR) for these groups based on data matched by age and sex and were adjusted for military rank and race/ethnicity.

RESULTS

Diabetes showed an OR of 1.469 [confidence interval (CI), 1.350-1.598]. Hip and knee arthritis produced an OR of 2.925 (CI, 2.685-3.187) and tobacco dependency showed an OR of 1.799 (CI, 1.762-1.836). The comparison of overweight to normal body mass index produced an OR of 1.334 (CI, 1.307-1.361) and the analysis of obese to normal body mass index had an OR of 1.556 (CI, 1.497-1.618). There failed to be a clinically significant association between military duty assignments and the presence of DDD.

CONCLUSIONS

Our research failed to show a clinical significance association between military duty assignment and DDD. However, we were able to identify a significant association between concomitant hip and knee osteoarthritis, obesity, diabetes, and tobacco dependency with the development of DDD.

LEVEL OF EVIDENCE

Level IV.

Annulo-Nucleoplasty Using Disc-Fx in the Management of Degenerative Lumbar Disc Pathology: How Long Can the Effect Last?

STUDY DESIGN

Prospective analysis.

OBJECTIVES

To evaluate 2-year clinical outcomes in patients undergoing Disc-FX for the management of low back pain (LBP) due to degenerate disc (DD) or contained lumbar disc herniation (CLDH). To study salient factors that can potentially influence the clinical outcomes.

METHODS

We analyzed the prospectively collected data of 51 patients who underwent Disc-FX procedure for DD or CLDH, nonresponsive to 6 months of nonoperative treatment. Clinical outcome measures collected were visual analogue scale (VAS), Oswestry Disability Index (ODI), and MacNab scores. These preoperative values were compared with respective values at immediate, 6 months, 1 year, and 2 years postoperation. Minimum clinically important difference values for these outcomes in accordance with previously published data was used to evaluate the effectiveness of Disc-FX intervention.

RESULTS

Of 51 patients, 84% had DD and 16% had CLDH. Significant improvement (P < .01) in VAS and ODI scores was observed at all assessment periods compared to the respective preoperative values. Based on the MacNab scores, there was significant increase (P < .01) in the proportion of patients with excellent/good MacNab outcomes at each time point after the procedure; 78% achieving excellent/good outcomes at 2-year follow-up. Ease of access to the disc space was significantly influencing VAS, ODI, and MacNab scores at 1-year and 2-year follow-ups. VAS and MacNab scores were negatively influenced by high body mass index and smoking status at 6 and 12 months postoperation.

CONCLUSIONS

Our data suggests that Disc-FX may be helpful in selected patients with symptomatic degenerative disc disease providing favorable outcomes lasting up to 2 years or more. The results were more favorable in patients with easier access to disc space.

Drop Body Syndrome: A Distinct Form of Adult Spinal Deformity

STUDY DESIGN

A retrospective observational study.

OBJECTIVE

This study examined the role of skeletal muscles in the spinal alignment of lumbar degenerative kyphosis (LDK).

SUMMARY OF BACKGROUND DATA

Adult spinal deformity (ASD) may present as LDK, which is unusual in that it typically lacks any coronal deformity.

METHODS

This retrospective study included 367 female patients with ASD. Demographic and radiographic data from LDKs were compared with those with other ASD. The LDK multifidus was also subjected to histological analysis. The muscle volume and strength were analyzed using whole-body dual x-ray absorptiometry and pulmonary function tests. Magnetic resonance images were used to determine the cross-sectional area (CSA) and fatty infiltration area (FIA) of the psoas and multifidus.

RESULTS

A total of 52 patients (15%) were classified as LDK. Compared with other ASDs, those with LDK had a significantly larger sagittal vertical axis (16.3 ± 5.0 cm), and pelvic incidence minus lumbar lordosis (52.8° ± 9.2°). The LDK had significantly lower CSA and higher FIA of the multifidus, but not in the psoas (multifidus CSA 223 ± 96 vs. 477 ± 129 mm, P < 0.001; FIA 82% vs. 31%, P < 0.001). Eighty-six percent of LDK had a multifidus CSA of less than 300 mm, and 82% had an FIA of more than 80%. Whole-body dual x-ray absorptiometry showed no significant difference in the other body sections between LDK and other ASDs. The percent-predicted peak expiratory flow was within normal range in 82% of the LDK. LDK multifidus specimens revealed diffuse, nonuniform muscular fibers and growth of the interstitium and adipose tissue, with no muscular inflammation. We redefined LDK as drop body syndrome, a distinct form of ASD.

CONCLUSION

Significantly decreased CSA and increased FIA of the multifidus were observed in LDK, whereas the muscle strength and volume of the other body sections were normal. These findings strongly suggest the presence of isolated lumbar extensor myopathy in LDK.

LEVEL OF EVIDENCE

4.

The Clinical Correlations between Diabetes, Cigarette Smoking and Obesity on Intervertebral Degenerative Disc Disease of the Lumbar Spine

Study Design

Retrospective analysis of a nationwide private insurance database. Chi-square analysis and linear regression models were utilized for outcome measures.

Purpose

The purpose of this study was to investigate any relationship between lumbar degenerative disc disease, diabetes, obesity and smoking tobacco.

Overview of Literature

Diabetes, obesity, and smoking tobacco are comorbid conditions known to individually have effect on degenerative disc disease. Most studies have only been on a small populous scale. No study has yet to investigate the combination of these conditions within a large patient cohort nor have they reviewed the combination of these conditions on degenerative disc disease.

Methods

A retrospective analysis of insurance billing codes within the nationwide Humana insurance database was performed, using PearlDiver software (PearlDiver, Inc., Fort Wayne, IN, USA), to identify trends among patients diagnosed with lumbar disc degenerative disease with and without the associated comorbidities of obesity, diabetes, and/or smoking tobacco. Patients billed for a comorbidity diagnosis on the same patient record as the lumbar disc degenerative disease diagnosis were compared over time to patients billed for lumbar disc degenerative disease without a comorbidity. There were no sources of funding for this manuscript and no conflicts of interest.

Results

The total number and prevalence of patients (per 10,000) within the database diagnosed with lumbar disc degenerative disease increased by 241.4% and 130.3%, respectively. The subsets of patients within this population who were concurrently diagnosed with either obesity, diabetes, tobacco use, or a combination thereof, was significantly higher than patients diagnosed with lumbar disc degenerative disease alone (p <0.05 for all). The number of patients diagnosed with lumbar disc degenerative disease and smoking rose significantly more than patients diagnosed with lumbar disc degenerative disease and either diabetes or obesity (p <0.05). The number of patients diagnosed with lumbar disc degenerative disease, smoking and obesity rose significantly more than the number of patients diagnosed with lumbar disc degenerative disease and any other comorbidity alone or combination of comorbidities (p <0.05).

Conclusions

Diabetes, obesity and cigarette smoking each are significantly associated with an increased diagnosis of lumbar degenerative disc disease. The combination of smoking and obesity had a synergistic effect on increased rates of lumbar degenerative disc disease. Patient education and preventative care is a vital goal in prevention of degenerative disc disease within the general population.

Relationship between cigarette smoking and hyperuricemia in middle-aged and elderly population: a cross-sectional study

The aim of the study was to estimate the cross-sectional association between cigarette smoking and the prevalence of hyperuricemia (HU) in the middle-aged and elderly males and females. A total of 3415 males and 2932 females were included in this study. HU was defined as SUA≥ 416 mmol/L for males and ≥360 mmol/L for females. The smoking status was classified into four categories based on daily smoking habit: (1) 0/day; (2) 1-10/day; (3) 11-20/day; and (4) >20/day. Multivariable logistic regressions were conducted to examine the aforementioned association. The prevalence of HU in the male and female sample was 25.0 and 10.0 %, respectively. In male subjects, the prevalence of HU in smokers (22.8 %) was significantly lower than that in non-smokers (26.5 %) (p = 0.016). Meanwhile, with adjustment for potential confounding factors, the prevalence of HU in smokers was still lower (OR = 0.83, 95 % CI 0.70-0.98, P = 0.033). Furthermore, a significantly inverse association between smoking status and HU was observed in the multivariable model. The multivariable-adjusted OR (95 % CI) for HU in the second, third and fourth category of smoking status was 0.84 (95 % CI 0.66-1.06), 0.90 (95 % CI 0.69-1.18) and 0.76 (95 % CI 0.58-0.99), respectively, compared with that in the first category. A clear trend (P for trend was 0.036) was observed. However, there was no significant association between cigarette smoking and HU in female subjects (P for trend was 0.739). This study indicated an inverse association between cigarette smoking and the prevalence of HU in the middle-aged and elderly male population, independent of some major confounding factors. The findings of this study expect further prospective studies to confirm the causal relationship.

Cigarette Smoking Is Associated with a Lower Concentration of CD105(+) Bone Marrow Progenitor Cells

Cigarette smoking is associated with musculoskeletal degenerative disorders, delayed fracture healing, and nonunion. Bone marrow progenitor cells (BMPCs), known to express CD105, are important in local trophic and immunomodulatory activity and central to musculoskeletal healing/regeneration. We hypothesized that smoking is associated with lower levels of BMPC. Iliac bone marrow samples were collected from individuals aged 18–65 years during the first steps of pelvic surgery, under IRB approval with informed consent. Patients with active infectious or neoplastic disease, a history of cytotoxic or radiation therapy, primary or secondary metabolic bone disease, or bone marrow dysfunction were excluded. Separation process purity and the number of BMPCs recovered were assessed with FACS. BMPC populations in self-reported smokers and nonsmokers were compared using the two-tailed t-test. 13 smokers and 13 nonsmokers of comparable age and gender were included. The average concentration of BMPCs was 3.52 × 10⁵/mL ± 2.45 × 10⁵/mL for nonsmokers versus 1.31 × 10⁵/mL ± 1.61 × 10⁵/mL for smokers (t = 3.2,  P = 0.004). This suggests that cigarette smoking is linked to a significant decrease in the concentration of BMPCs, which may contribute to the reduced regenerative capacity of smokers, with implications for musculoskeletal maintenance and repair.

Associations between cigarette smoking and pain among veterans

Individuals with chronic pain often report using cigarettes to cope, and smoking and chronic pain appear prevalent among US veterans. Pain may be a barrier to cigarette cessation and abstinence in this population. Because of physiological effects, smoking cigarettes may also interfere with pain management. A better understanding of how cigarette use relates to pain may assist in veteran cigarette cessation and pain management efforts. To assist these efforts, we searched the literature using keywords, such as "pain," "smoking," and "veteran," to identify 23 journal articles published from 1993 to 2013 that reported on studies examining pain and smoking variables among military or veteran populations. Studies found that veterans reported using cigarettes to cope with pain, there was greater occurrence of pain and disability among smokers in the military, and smoking increased the odds of veterans receiving an opioid prescription for pain and misusing opioids. Studies also found increased odds of pain and smoking among Veterans Health Administration patients with post-traumatic stress disorder when compared with those without post-traumatic stress disorder. Studies support an interaction between pain and smoking among veterans. However, the mechanisms underlying this relationship remain unclear. Future studies focused on this interaction would benefit veteran populations.

Relationship between cigarette smoking and radiographic knee osteoarthritis in Chinese population: a cross-sectional study

The purpose of this paper was to estimate the cross-sectional association between cigarette smoking and radiographic knee Osteoarthritis (OA) in Chinese population. A total of 3,789 subjects (1,796 females and 1,993 males) participated in this study. A subject was diagnosed with radiographic knee OA if Kellgren-Lawrence (K-L) grade ≥2 in at least one leg. The smoking status was classified into four levels based on the daily smoking habit: (1) 0/day; (2) 1-10/day; (3) 11-20/day; and (4) >20/day. Linear trend and multivariable logistic regression were conducted for statistical analysis. The prevalence of radiographic knee OA was 28.4 % among the subjects of this study. An inverse association was observed between cigarette smoking and radiographic knee OA in the linear trend test. Such association remained valid after adjusting the factors of age, gender, body mass index, betel quilt chewing status, physical activity, alcohol drinking status, mean total energy intake and educational level in the multivariable logistic regression. This study suggested a negative association between cigarette smoking and radiographic knee OA in the Chinese population. The findings of this study need to be confirmed by further prospective research.

Nicotine-induced chondrogenic differentiation of human bone marrow stromal cells in vitro

PURPOSE

Nicotine has been reported that it has a dose-dependent effect on matrix mineralization by human bone marrow cells. However, there is no relevant research concerning on chondrogenic differentiation potential of bone marrow stromal stem cells (BMSCs) treated with nicotine in vitro. The aims of the study were to examine the effects of nicotine (0, 10(-7), 10(-6) and 10(-5) M) on the proliferation and chondrogenic differentiation of BMSCs from three healthy donors in vitro.

METHODS

BMSCs proliferation was analyzed by CCK8 assay and real-time polymerase chain reaction was used to assay the expression of type II collagen, aggrecan, type I collagen and type X collagen. The proteoglycan content was stained by Alcian blue, and the sulfated glycosaminoglycan (sGAG) content of BMSCs was quantified spectrofluorometrically using dimethylmethylene blue.

RESULTS

The cell viability was not significantly impaired until up to a concentration of 10(-5) M nicotine. Nicotine promoted the proliferation and enhanced the expression of type II collagen at the level up to 10(-6) M (P < 0.05). The expression of aggrecan was reduced at the concentration of 10(-5) M nicotine at day 14 (P < 0.05), and there was no significant difference in aggrecan gene expression at 10(-7) and 10(-6) M nicotine levels compared to control group (n.s.). Also the fibroblastic and hypertrophic gene expressions were down-regulated in the chondrogenic medium with 10(-7)-10(-5) M nicotine (P < 0.05).

CONCLUSION

It was implied that local application of nicotine at an appropriate concentration may be a promising approach for enhancing chondrogenic differentiation capacity of BMSCs in cell-based cartilage tissue engineering. Also these results indicate that nicotine maybe a potentially useful drug for the treatment of Osteoarthritis.

Pain, nicotine, and smoking: research findings and mechanistic considerations

Tobacco addiction and chronic pain represent 2 highly prevalent and comorbid conditions that engender substantial burdens upon individuals and systems. Interrelations between pain and smoking have been of clinical and empirical interest for decades, and research in this area has increased dramatically over the past 5 years. We conceptualize the interaction of pain and smoking as a prototypical example of the biopsychosocial model. Accordingly, we extrapolated from behavioral, cognitive, affective, biomedical, and social perspectives to propose causal mechanisms that may contribute to the observed comorbidity between these 2 conditions. The extant literature was 1st dichotomized into investigations of either effects of smoking on pain or effects of pain on smoking. We then integrated these findings to present a reciprocal model of pain and smoking that is hypothesized to interact in the manner of a positive feedback loop, resulting in greater pain and increased smoking. Finally, we proposed directions for future research and discussed clinical implications for smokers with comorbid pain disorders. We observed modest evidence that smoking may be a risk factor in the multifactorial etiology of some chronically painful conditions and that pain may come to serve as a potent motivator of smoking. We also found that whereas animal studies yielded consistent support for direct pain-inhibitory effects of nicotine and tobacco, results from human studies were much less consistent. Future research in the emerging area of pain and smoking has the potential to inform theoretical and clinical applications with respect to tobacco smoking, chronic pain, and their comorbid presentation. (PsycINFO Database Record (c) 2011 APA, all rights reserved).

Smoking cigarettes as a coping strategy for chronic pain is associated with greater pain intensity and poorer pain-related function

Smoking cigarettes is prevalent among individuals with chronic pain. Some studies indicate nicotine reduces pain and others suggest it may cause or exacerbate pain. Participants in this cross-sectional study were 151 chronic pain patients from a large, urban VA medical center. Patients were divided into 3 groups: 1) nonsmokers; 2) smokers who deny using cigarettes to cope with pain; and 3) smokers who report using cigarettes to cope with pain. Patients who reported smoking as a coping strategy for chronic pain scored significantly worse compared with the other 2 groups on the majority of measures of pain-related outcome. Nonsmokers and smokers who denied smoking to cope did not differ on any variable examined. After controlling for the effects of demographic and clinical factors, smoking cigarettes as a coping strategy for pain was significantly and positively associated with pain intensity (P = .04), pain interference (P = .005), and fear of pain (P = .04). In addition to assessing general smoking status, a more specific assessment of the chronic pain patient's reasons for smoking may be an important consideration as part of interdisciplinary pain treatment.

PERSPECTIVE

This paper describes the relationship between smoking cigarettes as a mechanism to cope with chronic pain and pain-related outcome. Understanding this relationship may illuminate the broader relationship between smoking and chronic pain and provide new directions for effective interdisciplinary pain treatment.

Intervertebral disk nutrition: a review of factors influencing concentrations of nutrients and metabolites

The biomechanical behavior of the intervertebral disk ultimately depends on the viability and activity of a small population of resident cells that make and maintain the disk's extracellular matrix. Nutrients that support these cells are supplied by the blood vessels at the disks' margins and diffuse through the matrix of the avascular disk to the cells. This article reviews pathways of nutrient supply to these cells; examines factors that may interrupt these pathways, and discusses consequences for disk cell survival, disk degeneration, and disk repair.

Differential effects of nicotine and tobacco smoke condensate on human annulus fibrosus cell metabolism

Tobacco smoking increases the risk of intervertebral disc degeneration (IDD) and back pain, but the mechanisms underlying the adverse effects of smoking are largely unknown. Current hypotheses predict that smoking contributes to IDD indirectly through nicotine-mediated vasoconstriction which limits the exchange of nutrients between the discs and their surroundings. We alternatively hypothesize that direct contact of disc cells, that is, cells in the outermost annulus and those present along fissures in degenerating discs, with the vascular system containing soluble tobacco smoking constituents could perturb normal metabolic activities resulting in IDD. In this study, we tested our hypothesis by comparing the effects of direct exposure of human disc cells to tobacco smoke condensate and nicotine on cell viability and metabolic activity. We showed that smoke condensate, which contains all of the water-soluble compounds inhaled by smokers, exerts greater detrimental effects on human disc cell viability and metabolism than nicotine. Smoke condensate greatly induced an inflammatory response and gene expression of metalloproteinases while reduced active matrix synthesis and expression of matrix structural genes. Therefore, we have demonstrated that disc cell exposure to the constituents of tobacco smoke has negative consequences which have the potential to alter disc matrix homeostasis.

Nicotine promotes proliferation and collagen synthesis of chondrocytes isolated from normal human and osteoarthritis patients

The aims of the study were to show the direct effect of nicotine with different concentrations (0, 25, 50, and 100 ng/ml) on chondrocytes isolated from normal human and osteoarthritis patients, respectively. Microscopic observation was performed during the culture with an inverted microscope. Methyl thiazolyl tetrazolium (MTT) assay method was adopted to observe the influence of nicotine on the proliferation of chondrocytes, and real-time PCR and ELISA were used to assay the mRNA and protein expression of type II collagen and aggrecan, respectively. We discovered that the OA chondrocytes were similar to fibroblasts in shape and grow slower than normal chondrocytes. The proliferation of the two kinds of chondrocytes was increased in a concentration-dependent manner and in a time-dependent manner (P<0.05). Also, we found that the mRNA level of type II collagen were upregulated under 25-100 ng/ml nicotine doses both in the two kinds of chondrocytes compared with control. The expression of protein levels of type II collagen were synthesized in line with the increase in mRNA. No effect was observed on aggrecan synthesis with any nicotine dose. We concluded that nicotine has the same effect on both chondrocytes, obtained either from osteoarthritis patients or from normal human, and the positive effect of smoking in OA may relate to the alteration in metabolism of chondrocytes.

Outcome following lumbar disc surgery: the role of fibrosis

BACKGROUND

Failed-back surgery syndrome remains a challenge for spinal surgeons. It can be related to several causes, including poor surgical indication, misdiagnosis, surgical technique failure, spondilodiscitis and fibrosis. Fibrosis has been associated with a poorer outcome in lumbar disc surgery, although its role in the generation of symptoms is not yet clear. In this study, the authors have analyzed any possible correlation between the clinical outcome and the degree of fibrosis.

METHOD

Forty consecutive patients were enrolled in a prospective study. All of them had operations in the lower lumbar disc in a single level for the first time. Three months after the operation they were submitted to clinical outcome evaluations and questionnaires, including Numeric Pain Rating scales (NPR) for lumbar and leg pain, the McGill Pain Questionnaire, The Quebec Back Pain Disability scale (QBPD) and Straight Leg Raising test. These data were correlated with the degree of fibrosis as revealed by Magnetic Resonance Imaging (MRI).

FINDINGS

After 3 months, the NPR values for lumbar and leg pain ranged from 0 to 8 (mean 2.32 and 1.67 respectively). The values of the post-operative QBPD scale ranged from 1 to 71 (mean 25.9). Every patient showed a varied degree of fibrosis on MRI. However, statistical analysis depicted no significant correlation between fibrosis and a poorer clinical outcome for pain and disability.

CONCLUSIONS

The authors found no correlation between excessive fibrosis with lumbar and leg pain, disability or straight leg resistance. The role of fibrosis in the generation of symptoms in patients who have had lumbar disc surgery should be reevaluated.

Smoking and chronic back pain: analyses of the German Telephone Health Survey 2003

INTRODUCTION

Smoking represents the greatest avoidable risk for a large number of serious diseases. The goal of the present study was to investigate the connection between tobacco consumption and back pain, as such a link has yet to be clearly established.

METHODS

The analysis was based on the public use file of the German Telephone Health Survey 2003 (n = 8318), carried out by the Robert Koch Institute, Berlin. After exclusion of invalid cases, data on 7271 persons (total model) and 1998 persons (smoker model) were analyzed.

RESULTS

Multivariate data analysis clearly shows that not only daily smokers (OR 1.45, 95% CI 1.13 to 1.85) but also former smokers (OR 1.65, 95% CI 1.32 to 2.07) have a significantly higher chance of suffering from chronic back pain than non-smokers. Number of smoking years is the factor most significantly correlated with chronic back pain, while starting age and amount of tobacco consumed have no impact.

DISCUSSION

Owing to the cross-sectional design of this investigation it is not possible to conclude that smoking causes increased back pain through physical dysfunction. Nevertheless, the correlation should be analyzed in a longitudinal study because clarification of causality always represents potential for prevention.

Is preoperative occupation related to long-term pain in patients operated for lumbar disc herniation?

Lumbar disc herniation (LDH) is a common cause of back and sciatic pain. When clinical treatment fails, surgery may be indicated in selected patients. Although surgery is effective in most cases, some of these patients may have a poor outcome. Different factors may influence these results and poor adaptation at work is one well-known cause of treatment failure. This study examines 350 patients on long-term follow-up after surgery for first-time LDH. The relationship was analyzed between occupation before surgery and outcome (maintenance of lumbar and leg pain, satisfaction with the surgical treatment and return to work). The preoperative occupation (employed in public or private services, autonomous, unemployed, housewife, retired or student) and the exertion at work were analyzed as prognostic factors for different clinical outcomes. Although unemployed people had higher numerical analog scale for lumbar pain and retired patients had a higher leg pain, this difference was not statistically significant. Retired people were significantly less satisfied with the surgical result. Higher exertion at work showed a statistically insignificant higher level of pain and lower degree of satisfaction. The authors conclude that preoperative occupation was not a statistically significant factor in this series of patients.

In situ oxygen utilization in the rat intervertebral disc

Nucleus pulposus cells of the intervertebral disc have no endogenous vasculature and have thus been hypothesized to be hypoxic. This hypothesis was tested using 2-nitroimidazole, EF5, a drug that at low oxygen concentrations forms covalent adducts with cellular proteins. After administrating EF5 to rats, sections of the intervertebral disc were analysed for EF5 adducts. Drug adducts were quantified in tissue sections using a fluorescent monoclonal antibody. Although the level of EF5 fluorescence in all intervertebral disc tissues was low, the transition zone at the periphery of the nucleus pulposus exhibited the highest level of EF5 binding. To substantiate this result, tissue nitroreductase levels and drug pharmacology were evaluated. Nitroreductase levels were measured in whole discs under severe hypoxia. We noted that there was robust EF5 binding to cells in the annulus fibrosus and transition zone with modest binding to cells of the nucleus pulposus and endplate. High-performance liquid chromatography analysis indicated limitations in EF5 access to the nucleus pulposus, most probably related to the lack of vasculature and slow drug distribution through the gel-like interior of the disc. However, despite diffusion problems, the drug dose was determined to be sufficient to report the oxygen status of the nucleus pulposus cells. Based on these findings, we conclude that despite poor vascularization, the disc cells accommodate to the local environment by displaying a limited need for oxygen. Accordingly, the cells of the intervertebral disc are not severely hypoxic.

Variables Associated with Current Smoking Status in Chronic Pain Patients

OBJECTIVES

Smokers may report more pain and may be at greater risk for psychiatric comorbidity. Smoking may be a major problem in chronic pain patients (CPPs). The goal of this study was to determine if pain and psychiatric comorbidity are associated with smoking status in CPPs.

DESIGN

As part of a return-to-work grant study CPPs who could potentially return to work identified themselves as either current smokers (N=81) or nonsmokers (N=140). These two groups were compared on a large number of demographic, function, pain, disability, behavior, and psychiatric diagnoses variables gathered at admission into the grant study. The incidence of smoking was tested with either the student's t-test or chi-square to detect differences in continuous and categorical variables, respectively. Logistic regression was utilized to determine the predictive variables for smoking status by inputting significant independent variables (P<0.01) from the prior analyses.

SETTING

Pain facility.

RESULTS

Five variables were found to explain 38.8% of the variance for smoking status. These were education; race (Caucasian); cups of coffee per day; a diagnosis of current alcohol abuse/dependence; and personality disorder.

CONCLUSIONS

Smoking status in CPPs is associated with some variables that are similar for smoking in the general and psychiatric populations (education, race, alcoholism). However, a number of variables expected to be relevant (e.g., mood disorders) were not associated with smoking status in CPPs. These results may not be generalizable to all CPPs as they are derived from CPPs who are return-to-work candidates.

Cigarette smoking and the risk for cartilage loss and knee pain in men with knee osteoarthritis

OBJECTIVE

To examine the effects of smoking on cartilage loss and pain at the knee in individuals with knee osteoarthritis.

METHODS

159 men with symptomatic knee osteoarthritis who participated in a 30-month, prospective, natural history study of knee osteoarthritis were examined. The more symptomatic knee was imaged using magnetic resonance imaging (MRI) at baseline, and again at 15 and 30 months of follow-up. Cartilage was scored using the Whole-Organ MRI Score semiquantitative method at the medial and lateral tibiofemoral joints and at the patellofemoral joint. At baseline and follow-up visits, the severity of knee pain was assessed using a Visual Analogue Scale pain score (0-100 mm).

RESULTS

Among the 159 men, 19 (12%) were current smokers at baseline. Current smokers were younger (mean (standard deviation (SD)) age 62 (9) v 69 (9) years) and leaner (mean (SD) body mass index (BMI): 28.9 (3.2) v 31.3 (4.8) kg/m(2)) than men who were not current smokers. When adjusted for age, BMI and baseline cartilage scores, men who were current smokers were found to have an increased risk for cartilage loss at the medial tibiofemoral joint (odds ratio (OR) 2.3, 95% confidence interval (CI) 1.0 to 5.4) and the patellofemoral joint (OR 2.5, 95% CI 1.1 to 5.7). Current smokers also had higher adjusted pain scores at baseline (60.5 v 45.0, p<0.05) and at follow-up (59.4 v 44.3, p<0.05) than men who were not current smokers.

CONCLUSIONS

Men with knee osteoarthritis who smoke sustain greater cartilage loss and have more severe knee pain than men who do not smoke.

Low back problems and possible improvements in nursing jobs

AIM

This paper reports a study that aimed to evaluate the workload, to identify problems leading to the higher incidence rate of work-related low back injury among nurses in the orthopaedic and intensive care unit departments of the hospital, and to gather information about improvements that the nurses would like in the workplace.

BACKGROUND

The literature shows that low back injuries are common among nurses, and intervention programmes are needed to address this problem.

METHOD

The hospital injury records were examined in a retrospective study. In addition, a validated questionnaire was administered between January and May 2005 to 47 nurses (23 orthopaedic and 24 intensive care nurses). The questionnaire contained questions on workload, history of back injuries, problems, possible solutions and psychophysical measures of exertion.

FINDINGS

The life-time incidence and point prevalence of low back pain were 65% and 30%, respectively, in orthopaedic nurses, and 58% and 25%, respectively, in the intensive care nurses. The mean weight handled was reported to be 47 +/- 30 kg by the orthopaedic nurses and 26 +/- 10 kg by the intensive care nurses. The low back scored highest for body-part discomfort - 4.6 and 4.0, respectively, on a 10-point scale. The rate of perceived job exertion was 6.7 +/- 1.8 (very strong), and 5.8 +/- 1.9 (strong) on Borg's 10-point scale. The total effort required by the job, rated on Visual Analogue Scales, was 67 +/- 14% and 68 +/- 15% of the maximum, respectively. The Borg scores and the total effort according to the Visual Analogue Scale, and the Borg scores and force effort on the Visual Analogue Scale were moderately correlated (r = 0.53, P < 0.01 for both comparisons).

CONCLUSION

The methodology proposed here is practical for job evaluation and to design a participatory ergonomic intervention aiming at reducing low back injuries in nursing jobs. There are workload differences between nursing jobs. Lifting devices, biomechanical training, bigger rooms, adequate set-up and additional staff are suggested improvements.

A randomized clinical trial comparing two physiotherapy interventions for chronic low back pain

STUDY DESIGN

A randomized clinical trial with blinded assessment.

OBJECTIVES

To investigate the clinical efficacy of 2 active interventions for patients with chronic low back pain.

SUMMARY OF BACKGROUND DATA

Manual therapy and exercise prescription are treatments frequently prescribed for patients with chronic low back pain. The evidence for the relative benefit of these treatments is limited, and questions concerning the most appropriate type of intervention remain unanswered.

METHODS

Eighty patients with chronic low back pain (>3 months) were randomized to one of the following treatments, involving 8 treatments over 8 weeks; 1) one-to-one treatment involving 30 minutes of manual therapy (mobilizations to the spine) and spinal stabilization exercises, and 2) a 10 station exercise class involving aerobic exercises, spinal stabilization exercises, and manual therapy. Three physiotherapists led the hour long group with a maximum of 10 patients. Questionnaires were completed, and physical measurements were taken by a blinded observer before randomization, at the completion of treatment, and at 6 months and 12 months after the completion of treatment. The intention-to-treat principle was used in data analysis.

RESULTS

Eleven patients dropped out of the individual treatment sessions and 7 dropped out of the exercise group. There was a significant reduction (reduced disability) in the questionnaire score in both groups, and there were significant increases in range for all the physical movements tested in both groups. The exercise group was 40% more cost effective than the individual treatments.

CONCLUSION

Both forms of intervention were associated with significant improvement. On-going clinical research is necessary to provide guidance as to the clinical efficacy of various forms of intervention.

The effect of blocking a nutritional pathway to the intervertebral disc in the dog model

BACKGROUND

The hypothesis that injecting bone cement adjacent to one or both endplates would bring about degeneration in the intervening disc was tested.

METHODS

In 11 dogs, bone cement was injected just below the superior endplates of L1, L2, and L3 to block the nutritional supply through these endplates to the three intervertebral discs T13-L1, L1-L2, and L2-L3. In one other dog, both the superior and the inferior endplates of the same discs (T13-L1, L1-L2, and L2-L3) were blocked with bone cement. All 12 dogs were euthanized between 31 and 70 weeks after the surgery. The three experimental discs (T13-L1, L1-L2, and L2-L3) and two control discs (T12-T13 and L4-L5) were excised and assessed using enzyme-linked immunosorbent assay (ELISA) and histology.

RESULTS

Radiographs of the lumbar spine at the time of death did not show any signs of disc bulging, disc space narrowing, or peripheral osteophyte formation in any of the 12 dogs. The experimental discs as well as the control discs appeared normal in every dog. After the discs were bisected, they were carefully inspected for any visible signs of degeneration. The experimental discs showed no clear signs of disc degeneration and were not distinguishable from the control discs on a gross level. The numerical results from the ELISA showed that in the experimental discs as opposed to the control discs, there were significant increases in proteoglycan content in both the nucleus (P = 0.033) and annulus (P = 0.01) and clear histologic changes in some of the discs.

CONCLUSION

The results show that injecting bone cement adjacent to one or both endplates for up to 70 weeks does not produce degeneration in any visible form in the intervening disc. There were no disc bulging, no apparent annular fissures, and no disc spacing narrowing. There were, however, increases in protoglycan content in both the nucleus and the annulus and clear histologic changes in some of the discs.

[Association of working postures and some lifestyles with low back pain in a manufactory]

The aim of this study was to determine the relationship between work and low back pain (LBP) by examining both working postures and the workers' everyday lifestyle. Subjects were 118 male workers in a small-to-medium-sized factory having three kinds of workplaces: the slit line, the packing line, and the crane unit. Working posture analysis with OWAS and interviews were carried out. The result of posture analysis showed that the standing posture with both legs straight and back bent appeared most frequently in all three workplaces. Meanwhile, the prevalence of LBP was almost equal among these groups, with 70% of workers having experienced LBP in each group. But the main cause of LBP differed among the three groups. On the slit line, the result of regression analysis and interview suggested that exercises in the past affected the prevalence of LBP, and that aging and work made LBP worse. On the packing line, many workers were transferred to other positions after a few years, and thus might affect the prevalence of LBP in other workplaces. For the crane unit, it appeared that work in previous positions might affect the occurrence of LBP. Moreover, it seemed that activities in the workplace, rather than lifestyles, contribute to the occurrence of LBP in this factory.

Smoking and overweight as predictors of hospitalization for back disorders

STUDY DESIGN

A prospective cohort study.

OBJECTIVE

To study the relationship of smoking and overweight with severe back disorders leading to hospitalization.

SUMMARY OF BACKGROUND DATA

Many epidemiological studies have shown an association between smoking or overweight and back pain, but the results are still equivocal. Longitudinal studies are few.

METHODS

A cohort of metal industry employees (n = 902) was studied for lifestyle, work history, and health in 1973 by questionnaire and interview. The weight of the subjects was measured and body mass index (kg/m2) was calculated. Based on intensity and duration, smoking was categorized as: never smoked (reference), stopped smoking, smoked <or=9 or >9 pack-years. Information on hospital admissions from 1973 to 2000 from the Finnish Hospital Discharge Register was linked to the data. Seventy-five individuals had been admitted to hospital because of back disorders. Intervertebral disc disorders and other common back disorders were analyzed separately. Cox proportional hazards regression was used to estimate the time between the assessment of potential risk factors and the first hospitalization for a back disorder.

RESULTS

The rate ratio of heavy smokers (>9 pack-years) for hospitalization because of intervertebral disc disorders was 3.4 (95% confidence interval 1.3-9.0) as compared with never-smokers, allowing for other risk factors. Accordingly, the rate ratio of body mass index >27.5 kg/m2 was 2.7 (1.1-6.45) as compared with people with normal weight. The results retained when patients with chronic back disease at baseline were excluded from the analyses. Other back-related diagnoses of hospitalization were not consistently associated with smoking or overweight.

CONCLUSION

Heavy smoking and overweight predicted hospitalization for intervertebral disc disorders.

The three-dimensional architecture of the notochordal nucleus pulposus: novel observations on cell structures in the canine intervertebral disc

Cells from the nucleus pulposus of young (< 2 years) and old (> 5 years) non-chondrodystrophoid dogs were studied using routine histology, confocal laser scanning microscopy and transmission electron microscopy. The architecture of cell structures--from the tissue scale down to subcellular scale--was reported. Clusters of notochordal cells were observed in young nuclei pulposi, ranging from 10 to 426 cells each. These clusters resisted mechanical disruption and showed evidence of cell-cell signalling via gap junctions. Cells (30-40 microm in diameter) within the clusters had a physaliferous appearance, containing numerous large inclusions which ranged from 1 to 20 microm in diameter. The inclusions were surrounded by a dense actin cortex but were not contained by a lipid bilayer. The contents of the inclusions were determined not to be predominantly carbohydrate or neutral lipid as assessed by histochemical staining, but the exact composition of the contents remained uncertain. There were striking differences in the cell architecture of young vs. old nuclei pulposi, with a loss of both cell clusters and physaliferous cells during ageing. These observations demonstrate unique cell structures, which may influence our understanding of the differences between notochordal and chondrocytic cells in the nucleus pulposus. Such differences could have substantial impact upon how we think about development, degeneration and repair of the intervertebral disc.

Individual factors, occupational loading, and physical exercise as predictors of sciatic pain

STUDY DESIGN

In this prospective study, a cohort of 2077 workers free of sciatic pain and another cohort of 327 workers with severe sciatic pain were followed up for 1 year.

OBJECTIVE

To evaluate the effects of different risk factors on the incidence and persistence of sciatic pain.

SUMMARY OF BACKGROUND DATA

Sciatic pain seems to differ from other types of low back pain in terms of etiology, occurrence, and prognosis. Yet only a few studies of sciatic pain exist. The role of individual characteristics, occupational loading, and participation in different sports has rarely been assessed in a study with a prospective design among a working population.

METHODS

The subjects of this study, Finnish forest industry workers, replied to a modified version of the Nordic Questionnaire at the baseline of this study and after 1 year. The effects of the predictors on the 1-year incidence and persistence of sciatic pain were studied with multivariable logistic regression modeling.

RESULTS

Greater age, mental stress, smoking of long duration, and work-related twisting of the trunk increased the risk of incidental sciatic pain. Joggers had a lower risk for incidental sciatic pain, but a higher risk for persistent symptoms. Walking was positively associated with the risk of incidental pain. Greater age, mental stress, former smoking, jogging, and poor job satisfaction increased the risk for persistent severe sciatic pain.

CONCLUSIONS

The findings from this study suggest that mental stress and smoking are independent risk factors for incidental sciatic pain. Overall physical exercise and most of the sports activities, except jogging and walking, had no effect on sciatic pain. Physical workload factors seemed to be more involved in the onset of sciatic pain, whereas psychosocial factors were related to the persistence of symptoms.