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.

Dyslipidemia Is Positively Associated with Chronic Low Back Pain in Korean Women: Korean National Health and Nutrition Examination Survey 2010-2012

BACKGROUND

This study aimed to evaluate the association between chronic low back pain (CLBP) and chronic diseases, such as hypertension, diabetes, and dyslipidemia.

METHODS

This study was a retrospective analysis using data from the Korea National Health and Nutrition Examination Survey (KNHANES) between 2010-2012 and included women who answered a questionnaire in the KNHANES asking whether they had low back pain for ≥3 months. Participants were divided into non-CLBP and CLBP groups. For statistical analysis, the Student's t-test, chi-square test, Fisher's exact test, and logistic regression analysis were performed using SPSS.

RESULTS

Of 5961 participants, the non-CLBP group comprised 4098 women and the CLBP group comprised 1863. Adjusted logistic regression model revealed that dyslipidemia was positively associated with CLBP (odds ratio, 1.32; 95% confidence interval, 1.140, 1.530; p < 0.001). However, hypertension and diabetes were not associated with CLBP.

CONCLUSIONS

Our results suggest that proper treatment of dyslipidemia may contribute to lowering the risk of CLBP later in life.

The Impact of Diabetes Mellitus on Patient-Reported Outcomes of Chronic Low Back Pain with Modic Changes at One Year: A Prospective Cohort Study

STUDY DESIGN

Prospective cohort study.

OBJECTIVES

Diabetes mellitus (DM) is associated with unfavourable patient-reported outcomes after spine surgery. Chronic low back pain (CLBP) with Modic Changes (MCs) in the lumbar vertebrae, as observed on MRI, forms a specific subgroup. This study aims to investigate the potential influence of DM on CLBP with MCs.

METHODS

This study involved 259 patients with CLBP accompanied MCs. We recorded the patient-reported outcomes (visual analogue scale (VAS), Oswestry Disability Index (ODI), and Roland-Morris Disability Questionnaire (RMDQ)) at baseline, 3, 6, and 12 months. Multivariable linear regression analyses were performed to determine predictors of patient-reported outcomes.

RESULTS

103 patients had DM. Patients with DM exhibited higher VAS (P < .05), ODI (P < .001), and RMDQ (P < .001) scores at 3, 6, and 12 months, while patients without DM experienced more significant improvements in the scores over time (P < .001). Patients with DM reported longer durations of physical exercise (P = .007). Additionally, patients without DM had a significantly higher patient satisfaction index (P < .001) and a lower prevalence of hypertension (P < .001). Notably, significant differences were observed in the distribution of MCs of lumbar vertebrae (P = .034) and Pfirrmann grades of intervertebral disc degeneration between two groups (P < .001).

CONCLUSION

Patients with DM demonstrated poorer patient-reported outcomes compared to those without DM in 1-year. DM emerged as an independent predictor of adverse patient-reported outcomes. It can be utilized to enhance the management and treatment of CLBP in patients with MCs.

Symptoms in Hypertensive Patients Presented to the Emergency Medical Service: A Comprehensive Retrospective Analysis in Clinical Settings

BACKGROUND

Hypertension is a prevalent condition with a variety of accompanying symptoms. Gender differences, specific blood pressure readings, and early signs of organ complications present intricate interplays in hypertensive individuals.

OBJECTIVE

This study aimed to investigate the relationship between hypertension and its accompanying symptoms, emphasizing gender-specific differences and potential indicators of organ complications.

METHODS

Data from 2002 participants were analyzed from a retrospective study, focusing on the presentation of symptoms, blood pressure values, and potential organ complications associated with these symptoms.

RESULTS

Of the participants, 68.8% were women with an average age of 69. Women were, on average, 8 years older than men. The average systolic blood pressure (SBP) was 188 mmHg. High-blood pressure was accompanied by symptoms in 84.9% of participants. Among those with an SBP > 180 mmHg, headaches were reported by 24.7%, and dizziness by 15.7%. Interestingly, as SBP increased, heart palpitations reports diminished with a mere 4.8% of those with SBP > 180 mmHg noting this symptom. Younger men exhibited increased chest pain and heart palpitations, while younger women more commonly reported headaches and nausea/vomiting. A significant relationship was identified between pulse pressure (PP) and symptoms, with dizziness in women and chest pain/discomfort in men being most pronounced.

CONCLUSIONS

The study underlines the importance of in-depth research on hypertensive individuals for improved symptom recognition and management. The data highlight the gender and age-specific symptom presentations and their correlation with blood pressure metrics, suggesting a need for patient-specific intervention strategies.

Evidence of causal effects of blood pressure on back pain and back pain on type II diabetes provided by a bidirectional Mendelian randomization study

BACKGROUND CONTEXT

Cardiovascular risk factors (hypertension, dyslipidemia, and type II diabetes) have been proposed as risk factors for back pain. However, few longitudinal studies have found significant associations between cardiovascular risk factors and back pain, and these may be explained by confounding or reverse causation.

PURPOSE

To examine potential causal effects of cardiovascular risk factors on back pain, and vice versa.

STUDY DESIGN

Bidirectional Mendelian randomization (MR) study.

PATIENT SAMPLES

Genome-wide association studies (GWAS) with sample sizes between 173,082 and 1,028,947 participants.

OUTCOME MEASURES

Outcomes included (1) back pain associated with health care use (BP-HC) in the forward MR; and (2) seven cardiovascular phenotypes in the reverse MR, including 2 measurements used for the evaluation of hypertension (diastolic blood pressure and systolic blood pressure), 4 phenotypes related to dyslipidemia (LDL cholesterol, HDL cholesterol, total cholesterol, and triglycerides), and type II diabetes.

METHODS

We used summary statistics from large, publicly available GWAS for BP-HC and the 7 cardiovascular phenotypes to obtain genetic instrumental variables. We examined MR evidence for causal associations using inverse-variance weighted (IVW) analysis, Causal Analysis Using Summary Effect (CAUSE), and sensitivity analyses.

RESULTS

In forward MR analyses of seven cardiovascular phenotypes, diastolic blood pressure was associated with BP-HC across all analyses (IVW estimate: OR = 1.10 per 10.5 mm Hg increase [1.04-1.17], p-value = .001), and significant associations of systolic blood pressure with BP-HC were also found (IVW estimate: OR = 1.09 per 19.3 mm Hg increase [1.04-1.15], p-value = .0006). In reverse MR analyses, only type II diabetes was associated with BP-HC across all analyses (IVW estimate: OR = 1.40 [1.13-1.73], p-value = .002).

CONCLUSIONS

These findings from analyses of large, population-based samples indicate that higher blood pressure increases the risk of BP-HC, and BP-HC itself increases the risk of type II diabetes.

A bidirectional study of the association between insomnia, high-sensitivity C-reactive protein, and comorbid low back pain and lower limb pain

OBJECTIVES

To examine the possible bidirectional association between insomnia and comorbid chronic low back pain (LBP) and lower limb pain and to explore whether high-sensitivity C-reactive protein (hsCRP) amplifies these associations.

METHODS

We calculated adjusted risk ratios (RR) with 95% confidence intervals (CI) for the development of insomnia and mild-to-severe chronic LBP and lower limb pain at 11 years follow-up in participants aged ≥32 years and with hsCRP ≤10 mg/L at baseline in 2007-2008: 3,714 without chronic LBP or lower limb pain (sample 1) and 7,892 without insomnia (sample 2).

RESULTS

Compared to participants without chronic pain, participants with comorbid chronic LBP and lower limb pain had a RR of insomnia of 1.37 (95% CI 1.12-1.66). Compared with participants without insomnia, participants with insomnia did not have an increased risk of comorbid chronic LBP and lower limb pain (RR: 1.06, 95% CI 0.76-1.46); however, participants with insomnia had a RR of chronic LBP of 1.20 (95% CI 1.02-1.42). There was no strong amplifying effect of elevated hsCRP (3.00-10.0 mg/L) on these associations.

CONCLUSIONS

These findings suggest that elevated hsCRP does not amplify the associations between insomnia and mild-to-severe chronic LBP and lower limb pain. Further research using data on the temporal relation between insomnia, chronic pain, and inflammatory responses are required to fully understand the causal pathways.

EFFECT OF HYPERTENSION ON PAIN THRESHOLD IN PATIENTS WITH CHRONIC PAIN

Introduction: Little is known about the relationship between pain and hypertension (HT). This study aimed to analyze the effect of HT on pain sensitivity in patients with chronic musculoskeletal pain complaints. Methods: This analytical, cross-sectional study included 45 patients aged 29–75 years with HT. The control group comprised 44 normo/hypotensive patients aged 19–66 (P = 0.107). Education status, age, gender, height, weight, smoking, presence of diabetes mellitus, physical activity level, blood pressure measurement, anti-HT drug use, vital parameters, including heart rate, respiratory rate, and body temperature, were recorded for all participants. Results: The pain score was significantly higher in the HT group, with a mean of 72.1 ± 30.2 points (P = 0.008). Also, the HT group’s systolic blood pressure and pain score were significantly positively correlated (rho = 0.245, P = 0.02). The pulse rate was found to be significantly related to the pain score and pain threshold (P < 0.001); it was negatively correlated with algometer values (rho = –0.286, P = 0.015). Systolic pressure (P = 0.033) and BMI ( P < 0.001) were significantly different among the groups according to physical activity level. The Spearman correlation analysis showed a positive correlation of diastolic blood pressure with the body mass index (rho = 0.224, P = 0.036) and pain score (rho = 0.456, P < 0.001).  Conclusion: The present study showed that the pain complaint increases as the blood pressure and weight increase. Also, the pain threshold decreases as the heart rate increases. The pain threshold was lower in women than in men, independent of tension.

The Effects of Ambient Temperature on Lumbar Disc Herniation: A Retrospective Study

Purpose

This article was designed to provide critical evidence into the relationship between ambient temperature and intensity of back pain in people with lumbar disc herniation (LDH).

Methods

Data concerning patient's age, gender, diagnostic logout, admission time, discharge time, residence area, and work area (residence area and work area were used to ensure research area) from 2017 to 2019 were obtained from the Neck-Shoulder and Lumbocrural Pain Hospital in Jinan, China. A total of 1,450 hospitalization records were collected in total. The distributed lag non-linear model (DLNM) was used to evaluate the relationship between lag–response and exposure to ambient temperature. Stratification was based on age and gender. Days 1, 5, 20, and 28 prior to admission were denoted as lags 0, 5, 20, and 28, respectively.

Results

An average daily temperature of 15–23°C reduced the risk of hospitalization the most in men. Conversely, temperatures <10°C drastically increased hospitalization in men, particularly in lags 0–5 and lags 20–28. Men aged between 40 and 50 years old showed less effect in pain sensation during ambient temperature.

Conclusion

High or low ambient temperature can increase the hospitalization risk of LDH, and sometimes, the temperature effect is delayed.

Prevalence of pain in community-dwelling older adults with hypertension in the United States

Hypertension and pain are both prevalent conditions in the older adult population. We aimed to report the prevalence of pain discomforts and investigated the association between hypertension and pain discomforts among older adults in the United States. Data from the 2011 National Health and Aging Trends Study were analyzed. In-person interviews were conducted in 7601 adults ages ≥ 65 years. Prevalence of bothersome pain, activity-limiting pain, locations of pain and usage of pain medicine were evaluated. Demographics, comorbidities, and other covariates were compared between older adults with hypertension and those without. Multivariate regression was further performed to yield adjusted odd ratios. Among 6825 older adults, 4533 of them had a history of hypertension while 2272 of them had not. Prevalence of bothersome pain (57.12% versus 44.81%, p < 0.001) and activity-limiting pain (56.21% versus 46.12%, p < 0.001) were significantly higher in the hypertension group. After adjusting for all covariates, hypertension demonstrated a significant association with activity-limiting pain (OR 1.63, 95% CI 1.06 to 2.52, p = 0.02). In conclusion, pain was more prevalent in older Americans with hypertension. The positive association between hypertension and pain suggested that routine pain assessment and proper treatment would be required to improve the function and quality of life among older adults especially with hypertension.

Effects of body weight and fat mass on back pain - direct mechanical or indirect through inflammatory and metabolic parameters?

BACKGROUND

While reports indicate the association between obesity and back pain, its mechanism is still unclear. Thus, we aimed to investigate the effects of weight and its components on back pain in middle-aged women while considering direct mechanical and indirect effects via inflammatory and metabolic parameters.

METHODS

We used data from the Chingford 1000 Women Study, two follow-ups seven years apart. We assessed effects of weight, body mass index (BMI), total fat mass (TFM), total lean mass (TLM) and total bone mineral density (TBMD), measured by dual-energy X-ray absorptiometry, on back pain episode. We used inflammatory (C-reactive protein, interleukin-6, and tumour necrosis factor-alpha) and metabolic parameters (systolic and diastolic blood pressure, triglyceride, high-density lipoprotein cholesterol, and fasting blood glucose) as mediators of indirect effects. We investigated associations of interest cross-sectionally and longitudinally using binary logistic regression and parallel mediation model.

RESULTS

We included 826 Chingford middle-aged women (mean age=60.7, SD=5.9) from the first used follow-up in cross-sectional and mediation analyses and 645 women that attended the follow-up seven years later, in longitudinal analyses. We found that increased weight was directly associated with increased odds of having back pain episode (OR=1.02; 95% CI 1.01-1.03), similarly as BMI (OR=1.05; 95% CI 1.02-1.08) and TFM (OR=1.03; 95% CI 1.01-1.04) consistently across the cross-sectional and longitudinal models, but not TLM or TBMD. However, we did not find consistent indirect effects of weight or its components through measured inflammatory or metabolic parameters on back pain.

CONCLUSIONS

Our results show that in middle-aged women, weight, BMI and TFM are directly related to back pain, indicating prominence of mechanical loading effect.

Tissue Renin-Angiotensin System (tRAS) Induce Intervertebral Disc Degeneration by Activating Oxidative Stress and Inflammatory Reaction

Lumbar intervertebral disc degeneration (IDD) has been the major contributor to low back pain (LBP). IDD is an chronic inflammation process, with the activation of plentiful inflammation-related cytokines and ECM degradation-related enzymes. In the past few years, hypertension has been reported to correlate with LBP. In addition, the local tissue renin-angiotensin system (tRAS) has been identified in multiple tissues, including the spinal cord, skin, kidney, heart, and bone. Recently, tRAS has also been established in both bovine and human intervertebral disc tissues, especially in the degenerated disc tissue. However, the exact of tRAS and IDD remains unknown. In this present study, proteomic analysis, molecular biology analysis, and animal model were all used. Firstly, we revealed that tRAS was excessively activated in the human degenerated intervertebral disc tissue via proteomic analysis and molecular biology analysis. Then, in vitro experiment suggested that Ang II could decrease the cell viability of human NP cells and promote NP cell apoptosis, senescence, oxidative stress, and NLRP3 activation in human NP cells. In addition, Ang II could also trigger degeneration and fibrosis phenotype in human NP cells. Finally, the animal model demonstrated that the local activated ACE/Ang II axis in the NP tissue could accelerate IDD in aging spontaneously hypertensive rats (SHR). Collectively, the degenerated intervertebral disc tissue showed excessively activated tRAS, and local activated tRAS could induce NP cell senescence, apoptosis, oxidative stress, and inflammatory reaction to promote IDD. These biological effects of Ang II on human NP cells may provide novel insight into further treatment of IDD.

Prognostic factors for pain chronicity in low back pain: a systematic review

Supplemental Digital Content is Available in the Text.

Several prognostic factors are related to low back pain chronicity, and these should be taken into account when planning more comprehensive models in its prevention.

Low back pain is the leading cause for years lived in disability. Most people with acute low back pain improve rapidly, but 4% to 25% of patients become chronic. Since the previous systematic reviews on the subject, a large number of new studies have been conducted. The objective of this article was to review the evidence of the prognostic factors behind nonspecific chronic low back pain. A systematic literature search was performed without date limitation from the MEDLINE, Cochrane library, and Medic databases. Specific inclusion criteria were used, and risk factors before the onset of chronic symptoms were searched. Study quality was assessed by 2 independent reviewers. One hundred eleven full articles were read for potential inclusion, and 25 articles met all the inclusion criteria. One study was rated as good quality, 19 studies were rated as fair quality, and 5 articles were rated as poor quality. Higher pain intensity, higher body weight, carrying heavy loads at work, difficult working positions, and depression were the most frequently observed risk factors for chronic low back pain. Maladaptive behavior strategies, general anxiety, functional limitation during the episode, smoking, and particularly physical work were also explicitly predictive of chronicity. According to this systematic review, several prognostic factors from the biomechanical, psychological and psychosocial point of view are significant for chronicity in low back pain.

Impact of antihypertensive treatment on resiliency to clinical pain

OBJECTIVES

Although progress has been made in the regulation of hypertension over the past decades, the USA and some other countries have faced a significant rise in incidence of chronic pain management cases during the same period. Studies of the relationship between pain and blood pressure (BP) regulations propose that these two processes may be interconnected. Studies of effects of antihypertensive treatment on pain in general and its chronification have never been reviewed.

METHODS

A narrative review of respective studies with analysis of credibility of the findings was conducted.

RESULTS

Some studies have suggested that aggressive reduction of high BP may contribute to a return in pain symptoms and may require more aggressive, long-term pain management. Other studies propose that long-term antihypertensive medication could also increase the risk for new cases of chronic pain. Pain initiates a central neuroplastic resetting of the baroreceptor activation accounting for sustained increase of BP with an adaptive 'pain-killing' or maladaptive 'pain-complication' effect associated with pain chronification, and these mechanisms may be moderated by antihypertensive medications. However, different antihypertensive drugs and nondrug treatments may diversely affect pain mechanisms at different stages of treatments.

CONCLUSION

Uncontrollable reduction of high BP in some patients with hypertension could increase the risk for chronic pain incidence and its severity. Practical recommendations in BP control should be reconsidered to take into account patients' chronic pain. Further research is needed of moderation effects of different antihypertensive manipulations on pain to improve pain management in these patients.

The effect of indirect vision skills on head and shoulder posture amongst Korean dental hygienists

OBJECTIVES

This study aimed to investigate the effects of indirect vision skills on head and shoulder posture in dental hygienists.

MATERIALS AND METHODS

This cross-sectional study included a total of 100 female clinical dental hygienists. It evaluated musculoskeletal symptoms of the neck, shoulders and back, head and shoulder posture (craniovertebral angle [CVA] and sagittal shoulder posture angle [SSPA]). Indirect vision skills were assessed using the O'Connor tweezer test under indirect vision with a mirror. To analyse factors associated with the CVA and SSPA, an independent t test, one-way ANOVA, and multiple linear regression analysis were conducted, respectively.

RESULTS

The body region in which the greatest number of symptoms of work-related musculoskeletal disorders was recognised was the neck (89.0%). In the multiple linear regression model, which adjusted for other factors associated with musculoskeletal disorders, dental hygienists with poor indirect vision skills showed relatively small SSPA value (P < .05). However, indirect vision skills were not associated with the CVA value.

CONCLUSIONS

Good indirect vision skills contribute to the prevention of rounded shoulders in dental hygienists. Therefore, where possible, dental hygienists should perform clinical procedures using indirect vision with a dental mirror to maintain a balanced posture and reduce flexion of the back or the neck. A dental hygiene curriculum should include training to improve clinical skills, as well as education regarding dental ergonomics and a monitoring system to determine whether ergonomic principles are well observed.

Chronic pain-related changes in cardiovascular regulation and impact on comorbid hypertension in a general population: the Tromsø study

Heart rate variability (HRV) and baroreflex sensitivity (BRS) are indexes reflecting the ability to maintain cardiovascular homeostasis amidst changing conditions. Evidence primarily from small studies suggests that both HRV and BRS may be reduced in individuals with chronic pain (CP), with potential implications for cardiovascular risk. We compared HRV and BRS between individuals with CP (broadly defined) and pain-free controls in a large unselected population sample. Participants were 1143 individuals reporting clinically meaningful CP and 5640 pain-free controls who completed a 106-second cold pressor test (CPT). Participants self-reported hypertension status. Resting HRV and BRS were derived from continuous beat-to-beat blood pressure recordings obtained before and after the CPT. Hierarchical regressions for the pre-CPT period indicated that beyond effects of age, sex, and body mass index, the CP group displayed significantly lower HRV in both the time domain (SDNN and rMSSD) and frequency domain (high-frequency HRV power), as well as lower BRS. Results were somewhat weaker for the post-CPT period. Mediation analyses indicated that for 6 of 7 HRV and BRS measures tested, there were significant indirect (mediated) effects of CP status on the presence of comorbid hypertension via reduced HRV or BRS. Results confirm in the largest and broadest sample tested to date that the presence of CP is linked to impaired cardiovascular regulation and for the first time provide support for the hypothesis that links between CP and comorbid hypertension reported in previous population studies may be due in part to CP-related decrements in cardiovascular regulation.

Acupuncture and Neural Mechanism in the Management of Low Back Pain-An Update

Within the last 10 years, the percentage of low back pain (LBP) prevalence increased by 18%. The management and high cost of LBP put a tremendous burden on the healthcare system. Many risk factors have been identified, such as lifestyle, trauma, degeneration, postural impairment, and occupational related factors; however, as high as 95% of the cases of LBP are non-specific. Currently, LBP is treated pharmacologically. Approximately 25 to 30% of the patients develop serious side effects, such as drowsiness and drug addiction. Spinal surgery often does not result in a massive improvement of pain relief. Therefore, complementary approaches are being integrated into the rehabilitation programs. These include chiropractic therapy, physiotherapy, massage, exercise, herbal medicine and acupuncture. Acupuncture for LBP is one of the most commonly used non-pharmacological pain-relieving techniques. This is due to its low adverse effects and cost-effectiveness. Currently, many randomized controlled trials and clinical research studies have produced promising results. In this article, the causes and incidence of LBP on global health care are reviewed. The importance of treatment by acupuncture is considered. The efforts to reveal the link between acupuncture points and anatomical features and the neurological mechanisms that lead to acupuncture-induced analgesic effect are reviewed.

[Baroreflex sensitivity and chronic pain : Pathogenetic significance and clinical implications]

The interaction of cardiovascular dynamics and pain perception is an important component of intrinsic pain regulation. In healthy subjects acute pain stimuli cause increased sympathetic arousal and increased mean arterial pressure. Arterial baroreceptors sense phasic blood pressure changes and relay the information to the lower brainstem via the dorsomedial nucleus tractus solitarius (dmNTS). Projections in the brainstem and also higher cortical areas result in elevation of blood pressure as part of the autonomic nervous system as well as modulation of sleep, anxiety and pain. In healthy subjects there is an inverse relationship between blood pressure and pain sensitivity but this relationship is impaired in chronic pain patients. Persistent stress, pain behavior and classical and operant conditioning mechanisms reduce baroreflex sensitivity (BRS) and dmNTS activity in a subgroup of patients. This leads to a decrease of autonomic regulatory function as well as reduced pain inhibition. Importantly, baroreflex function can be modulated by cognitive and affective processes. This article reviews the role of the baroreflex arc as a possible crucial factor in the development and maintenance of chronic pain. The importance of learning mechanisms is described. Mechanism-based individualized treatment approaches for patients with hypertensive stress reactivity are also critically discussed.

Resting blood pressure differentially predicts time course in a tonic pain experiment

Resting blood pressure (BP) shows a negative relationship with pain sensitivity (BP-related hypoalgesia). In chronic pain conditions, this relationship is inverted. The precise mechanisms responsible for the inversion are unknown. Using a tonic pain protocol, we report findings closely resembling this inversion in healthy participants. Resting BP and state measures of anxiety and mood were assessed from 33 participants (21 female). Participants then immersed their dominant hand in painfully hot water (47 °C) for five trials of 1-min duration, with 30-s intertrial intervals. Throughout the trials, participants continually registered their pain. After a 35-min intermission, the trial sequence was repeated. A disassociation of the negative relationship of resting systolic BP (as per Trial 1) was found using hierarchical linear modeling (p < .001, R(2)  = .07). The disassociation unfolds over each consecutive trial, with an increasingly positive relationship. In Sequence 2, the initially negative relationship is almost completely absent. Furthermore, the association of BP and pain was found to be moderated by anxiety, such that only persons with low anxiety exhibited BP hypoalgesia. Our findings expand the existing literature by incorporating anxiety as a moderator of BP hypoalgesia. Furthermore, the protocol emulates the changing relationship between BP and pain observed in chronic pain patients. The protocol has potential as a model for chronic pain; however, future research should determine if similar physiological systems are involved. The finding holds potential diagnostic or prognostic relevance for certain clinical pain conditions, especially those involving dysfunction of the descending modulation of pain.

Is there a U-shaped relationship between physical activity in leisure time and risk of chronic low back pain? A follow-up in the HUNT Study

Background

Physical activity in leisure time is often considered to have favourable effects on the risk of low back pain (LBP), but demonstrating a definite association in epidemiological studies has proven difficult. The purpose of the present study was to explore associations between physical activity and risk of chronic LBP in an adult population and to investigate whether relationships are limited to certain age groups or to females or males. A particular objective was to determine whether support could be found for a U-shaped relationship, with both low and high activity levels carrying greater risk.

Methods

The relationship between physical activity and risk of chronic LBP was examined in a Norwegian prospective study using data from the community-based HUNT2 and HUNT3 surveys. Participants were 9616 women and 8452 men without LBP at baseline, who reported after 11 years whether they suffered from LBP. Associations between baseline physical activity in leisure time and risk of chronic LBP at end of follow-up were evaluated by generalized linear modelling with adjustment for potential confounders.

Results

Significant associations between leisure time physical activity and risk were observed in both sexes after age adjustment, mainly suggesting inverse relationships. Women participating in hard physical activity 1–2 h per week had a relative risk (RR) of chronic LBP of 0.81 (95 % CI 0.71–0.93) compared to those with only light physical activity less than 1 h per week. The corresponding RR in men was 0.71 (95 % CI 0.60–0.85). After adjustment for education, employment, occupational activity, body mass index (BMI) and smoking, significant relationships could only be demonstrated in those aged 50 years or more at baseline. The associations differed between female educational groups, with more U-shaped relationships being observed among women with basic education only.

Conclusion

No strong support was found overall for U-shaped relationships. However, no further general decrease in risk was seen among those with 3 h or more of hard physical activity per week. The contrasts observed between female educational groups may reflect different preferences regarding specific strenuous activities. Men aged 50 years or more seem in particular to benefit from hard physical activities.

Joint Mobilization Enhances Mechanisms of Conditioned Pain Modulation in Individuals With Osteoarthritis of the Knee

STUDY DESIGN

An experimental laboratory study with a repeated-measures crossover design.

BACKGROUND

Treatment effects of joint mobilization may occur in part by decreasing excitability of central nociceptive pathways. Impaired conditioned pain modulation (CPM) has been found experimentally in persons with knee and hip osteoarthritis, indicating impaired inhibition of central nociceptive pathways. We hypothesized increased effectiveness of CPM following application of joint mobilization, determined via measures of deep tissue hyperalgesia.

OBJECTIVE

To examine the effect of joint mobilization on impaired CPM.

METHODS

An examination of 40 individuals with moderate/severe knee osteoarthritis identified 29 (73%) with impaired CPM. The subjects were randomized to receive 6 minutes of knee joint mobilization (intervention) or manual cutaneous input only, 1 week apart. Deep tissue hyperalgesia was examined via pressure pain thresholds bilaterally at the knee medial joint line and the hand at baseline, postintervention, and post-CPM testing. Further, vibration perception threshold was measured at the medial knee epicondyle at baseline and post-CPM testing.

RESULTS

Joint mobilization, but not cutaneous input intervention, resulted in a global increase in pressure pain threshold, indicated by diminished hyperalgesic responses to pressure stimulus. Further, CPM was significantly enhanced following joint mobilization. Diminished baseline vibration perception threshold acuity was enhanced following joint mobilization at the knee that received intervention, but not at the contralateral knee. Resting pain was also significantly lower following the joint intervention.

CONCLUSION

Conditioned pain modulation was enhanced following joint mobilization, demonstrated by a global decrease in deep tissue pressure sensitivity. Joint mobilization may act via enhancement of descending pain mechanisms in patients with painful knee osteoarthritis.

Association between Hypertension and the Prevalence of Low Back Pain and Osteoarthritis in Koreans: A Cross-Sectional Study

BACKGROUND

Hypertension and musculoskeletal disorders are highly prevalent in adult populations. The objective of this study was to investigate the association between hypertension and prevalence of low back pain (LBP) and osteoarthritis in Koreans.

METHODS

A total 17,128 participants (age ≥20 years) who answered low back pain and osteoarthritis items in the 4th Korean National Health and Nutrition Examination Survey (2007-2009) were analyzed. Odds ratios were calculated using logistic regression and were adjusted for age, sex, income level, education, occupation, BMI, smoking status, alcohol consumption, and physical activity.

RESULTS

Lifetime prevalence of LBP in hypertensive subjects was 34.4%, and that of osteoarthritis 26.2%. LBP prevalence was significantly lower in hypertensives (fully adjusted OR 0.79; 95% CI 0.70-0.90), and both LBP and osteoarthritis prevalence was significantly lower in participants with systolic blood pressure ≥140mmHg than those with <120mmHg (fully adjusted OR 0.81; 95% CI 0.70-0.94, and 0.81; 95% CI 0.68-0.96, respectively). Prevalence of LBP in subjects with diastolic blood pressure ≥90mmHg was also significantly lower than those with <80mmHg (fully adjusted OR 0.73; 95% CI 0.63-0.85). LBP and osteoarthritis prevalence did not differ by systolic or diastolic blood pressure interval in respondents taking antihypertensive medication. LBP and osteoarthritis prevalence increased with longer hypertension duration (fully adjusted p for trend 0.028, and 0.0008, respectively).

CONCLUSIONS

Hypertension showed an inverse relationship with LBP and osteoarthritis prevalence, which may be ascribed to hypertension-associated hypalgesia, and antihypertensive medication intake and longer hypertension duration attenuated this association.

Do abnormal serum lipid levels increase the risk of chronic low back pain? The Nord-Trøndelag Health Study

Background

Cross-sectional studies suggest associations between abnormal lipid levels and prevalence of low back pain (LBP), but it is not known if there is any causal relationship.

Objective

The objective was to determine, in a population-based prospective cohort study, whether there is any relation between levels of total cholesterol, high density lipoprotein (HDL) cholesterol and triglycerides and the probability of experiencing subsequent chronic (LBP), both among individuals with and without LBP at baseline.

Methods

Information was collected in the community-based HUNT 2 (1995–1997) and HUNT 3 (2006–2008) surveys of an entire Norwegian county. Participants were 10,151 women and 8731 men aged 30–69 years, not affected by chronic LBP at baseline, and 3902 women and 2666 men with LBP at baseline. Eleven years later the participants indicated whether they currently suffered from chronic LBP.

Results

Among women without LBP at baseline, HDL cholesterol levels were inversely associated and triglyceride levels positively associated with the risk of chronic LBP at end of follow-up in analyses adjusted for age only. Adjustment for the baseline factors education, work status, physical activity, smoking, blood pressure and in particular BMI largely removed these associations (RR: 0.96, 95% CI: 0.85–1.07 per mmol/l of HDL cholesterol; RR: 1.16, 95% CI: 0.94–1.42 per unit of lg(triglycerides)). Total cholesterol levels showed no associations. In women with LBP at baseline and men without LBP at baseline weaker relationships were observed. In men with LBP at baseline, an inverse association with HDL cholesterol remained after complete adjustment (RR: 0.83, 95% CI: 0.72–0.95 per mmol/l).

Conclusion

Crude associations between lipid levels and risk of subsequent LBP in individuals without current LBP are mainly caused by confounding with body mass. However, an association with low HDL levels may still remain in men who are already affected and possibly experience a higher pain intensity.