Menopausal hormone therapy, oral contraceptives and risk of chronic low back pain: the HUNT Study.

BACKGROUND: There are indications that use of menopausal hormone therapy (MHT) and oral contraceptives (OC) increases the risk of low back pain (LBP), with higher oestrogen levels involved in the underlying mechanisms. The purpose of the present study was to investigate associations between use of systemic MHT or OC and risk of chronic LBP in a large population-based data set. METHODS: Data were obtained from two surveys in the Trøndelag Health Study in Norway, HUNT2 (1995-1997) and HUNT3 (2006-2008). A cross-sectional study of association between use of systemic MHT and prevalence of chronic LBP comprised 12,974 women aged 40-69 years in HUNT2, with 4007 women reporting chronic LBP. A cohort study involving MHT comprised 6007 women without chronic LBP at baseline in HUNT2, and after 11 years 1245 women reported chronic LBP at follow-up in HUNT3. The cross-sectional study of association with use of OC included 23,593 women aged 20-69 years in HUNT2, with 6085 women reporting chronic LBP. The corresponding cohort study included 10,586 women without chronic LBP at baseline in HUNT2, of whom 2084 women reported chronic LBP in HUNT3. Risk of chronic LBP was examined in both study designs in generalised linear models with adjustment for potential confounders. RESULTS: In the cohort study, current users of systemic MHT at baseline showed a greater risk of chronic LBP (relative risk (RR) 1.30; 95% CI: 1.14-1.49; compared with never users). The risk increased according to duration of MHT use (P for linear trend = 0.003). Known users of systemic MHT based exclusively on oestrogen experienced the highest risk (RR 1.49; 95% CI: 1.16-1.91), but an increased risk was also seen among known users of oestrogen-progestin combination MHT (RR 1.35; 95% CI: 1.16-1.57). A slight increase in risk of chronic LBP was found in the cohort study among former users of OC (RR 1.17; 95% CI: 1.06-1.30; compared with never users). CONCLUSIONS: Long-lasting use of systemic MHT, in particular therapy based on oestrogen only, is associated with greater risk of chronic LBP. Having been a user of OC most likely entails a minor increase in risk.

Associations between the number of children, age at childbirths and prevalence of chronic low back pain: the Nord-Trøndelag Health Study.

BACKGROUND: Associations between childbirths and subsequent risk of low back pain (LBP) have not been clarified. Changes in sex hormone levels or lumbar posture during pregnancy may have an impact on LBP later in life. The purpose of this study was to explore associations between the number of childbirths, age at childbirths and prevalence of chronic LBP in a general population of women. METHODS: Data were obtained from the Norwegian community-based Nord-Trøndelag Health Study, HUNT2 (1995-1997). Women aged 20-69 years indicated whether they suffered from chronic LBP, defined as LBP persisting at least 3 months continuously during last year. Information about LBP was collected from 3936 women who had experienced no childbirths, 3143 women who had delivered one child only and 20,584 women who had delivered 2 or more children. Of these, 7339 women reported chronic LBP. The 595 women who were pregnant when information was collected were considered separately, regardless of previous births, with 80 women reporting chronic LBP. Associations with prevalence of chronic LBP were examined by generalised linear modelling with adjustment for potential confounders in a cross-sectional design. RESULTS: Women who had delivered one child only showed a higher prevalence of chronic LBP than women with no childbirths (prevalence ratio (PR) 1.11; 95% CI: 1.01-1.22). Among women with one or more childbirths, no overall change in prevalence could be demonstrated with an increasing number of children in analyses adjusted for age at first delivery. In women with at least two childbirths, an age less than 20 years at first childbirth was associated with an increased prevalence of chronic LBP (PR 1.36; 95% CI: 1.25-1.49; compared with age 25-29 years). No association was observed between age at last delivery and chronic LBP. The lowest prevalence of chronic LBP was found among women who were currently pregnant (PR 0.80; 95% CI: 0.63-1.00; compared with women with no childbirths). CONCLUSIONS: Having experienced at least one childbirth seems to be associated with a higher prevalence of chronic LBP later in life. A young age at first childbirth is also associated with a long-lasting increased prevalence.

Lifestyle factors and risk of migraine and tension-type headache. Follow-up data from the Nord-Trøndelag Health Surveys 1995-1997 and 2006-2008.

AIMS: The aim of this population-based historical cohort study was to investigate the influence of lifestyle factors on the risk of developing migraine or tension-type headache (TTH). METHODS: Data from the Nord-Trøndelag Health Study performed in 1995-1997 and 2006-2008 was used. A total of 15,276 participants without headache at baseline were included. A Poisson regression was used to evaluate the associations between lifestyle factors and risk ratios (RRs) of migraine and TTH 11 years later. Precision of the estimates was assessed by 95% confidence interval (CIs). RESULTS: Increased risk of migraine (RR 1.30, 95% CI 1.11-1.52) was found in smokers (past or current) compared to those who had never smoked. Hard physical exercise 1-2 hours per week reduced the risk of migraine (OR 0.71, 95% CI 0.54-0.94) compared to inactivity, and the risk of migraine was also lower among those who consumed alcohol (RR 0.73, 95% CI 0.57-0.94) compared to abstainers. No association was found between smoking, physical activity, alcohol use and risk of TTH. CONCLUSIONS: The main finding was that current and previous smoking was associated with increased risk of migraine, but not of TTH.

Migraine as a predictor of mortality: The HUNT study.

BACKGROUND: There is conflicting evidence for the association between migraine and increased mortality risk. The aim of this study was to investigate the relationship between migraine and non-migrainous headache, and all-cause mortality and cardiovascular mortality. METHODS: In this prospective population-based cohort study from Norway, we used baseline data from the second Nord-Trøndelag Health Survey (HUNT2), performed between 1995 and 1997 in the County of Nord-Trøndelag. These data were linked with a comprehensive mortality database with follow-up through the year 2011. A total of 51,853 (56% of invited) people were categorized based on their answers to the headache questions in HUNT2 (headache free, migraine or non-migrainous headache). Hazard ratios (HRs) of mortality during a mean of 14.1 years of follow-up were estimated using Cox regression. RESULTS: During the follow-up period 9408 died, 4321 of these from cardiovascular causes. There was no difference in all-cause mortality between individuals with migraine and non-migrainous headache compared to those without headache or between headache status and mortality by cardiovascular disease. There was, however, among men with migraine without aura a reduced risk of death by cardiovascular diseases (HR 0.72, 95% confidence interval 0.56-0.93). This relationship was not evident in women. CONCLUSION: In this large, prospective cohort study there was no evidence for a higher all-cause mortality or cardiovascular mortality among individuals with migraine.

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.

Does the risk of chronic low back pain depend on age at menarche or menopause? A population-based cross-sectional and cohort study: the Trøndelag Health Study.

OBJECTIVE: In most population-based studies of low back pain (LBP), women have a higher risk than men, possibly reflecting hormonal influences. The aim of this study was to explore associations between age at menarche and menopause and risk of chronic LBP. DESIGN: Population-based cross-sectional and cohort study designs. SETTING: The HUNT2 and HUNT3 medical surveys of the entire population of Nord-Trøndelag County in Norway. MAIN OUTCOME MEASURE: Prevalence or risk of chronic LBP, defined as LBP persisting at least 3 months continuously during last year. PARTICIPANTS: Associations between age at menarche and prevalence of chronic LBP were examined in cross-sectional data from HUNT2, comprising 27 697 women aged 20-69 years, with 7300 women reporting LBP. The corresponding cohort data included 11 659 women without LBP at baseline in HUNT2, with 2353 women reporting LBP at follow-up 11 years later in HUNT3. Cross-sectional data on age at menopause or premenopausal status included 11 332 women aged 40-69 years, with 3439 women reporting chronic LBP. Corresponding cohort data included 7893 women without LBP at baseline, of whom 1100 developed LBP. METHODS: Associations between age at menarche or menopause and risk of chronic LBP were examined by generalised linear modelling. RESULTS: A U-shaped association was indicated between age at menarche and risk of chronic LBP, both in the cross-sectional and cohort studies. Age at menarche ≤11 years was associated with an increased risk of chronic LBP, with a relative risk of 1.32 (95% CI 1.15 to 1.52), compared with age 14 years at menarche, after relevant adjustments. Corresponding cross-sectional crude absolute risks were 32% and 25%, respectively. No association was established between age at menopause and risk of LBP. Being premenopausal had no influence on risk. CONCLUSIONS: In contrast to results for age at menopause, the association with age at menarche suggests that hormonal factors affect the risk of LBP.

Brain-specific genes contribute to chronic but not to acute back pain.

Introduction: Back pain is the leading cause of disability worldwide. Although most back pain cases are acute, 20% of acute pain patients experience chronic back pain symptoms. It is unclear whether acute pain and chronic pain have similar or distinct underlying genetic mechanisms. Objectives: To characterize the molecular and cellular pathways contributing to acute and chronic pain states. Methods: Cross-sectional observational genome-wide association study. Results: A total of 375,158 individuals from the UK Biobank cohort were included in the discovery of genome-wide association study. Of those, 70,633 (19%) and 32,209 (9%) individuals met the definition of chronic and acute back pain, respectively. A total of 355 single nucleotide polymorphism grouped into 13 loci reached the genome-wide significance threshold (5x10-8) for chronic back pain, but none for acute. Of these, 7 loci were replicated in the Nord-Trøndelag Health Study (HUNT) cohort (19,760 chronic low back pain cases and 28,674 pain-free controls). Single nucleotide polymorphism heritability was 4.6% (P=1.4x10-78) for chronic back pain and 0.81% (P=1.4x10-8) for acute back pain. Similar differences in heritability estimates between acute and chronic back pain were found in the HUNT cohort: 3.4% (P=0.0011) and 0.6% (P=0.851), respectively. Pathway analyses, tissue-specific heritability enrichment analyses, and epigenetic characterization suggest a substantial genetic contribution to chronic but not acute back pain from the loci predominantly expressed in the central nervous system. Conclusion: Chronic back pain is substantially more heritable than acute back pain. This heritability is mostly attributed to genes expressed in the brain.

Increasing prevalence of chronic musculoskeletal complaints. A large 11-year follow-up in the general population (HUNT 2 and 3).

OBJECTIVES: To assess the prevalence of chronic musculoskeletal complaints (MSCs) in a large adult population, and to determine any changes in prevalence during an 11-year period. METHODS: This study involved two large cross-sectional surveys (Helseundersøkelsen i Nord-Trøndelag [HUNT] 2 and 3) of inhabitants in Nord-Trøndelag county aged ≥20 years performed in 1995-97 (N = 92,936) and 2006-08 (N = 94,194). Attendance rates were 70 and 42%, respectively. Respondents with chronic MSCs were identified through the screening question "Have you during the last year continuously for at least 3 months had pain and/or stiffness in muscles and joints?" The reliability of the screening question was evaluated in a random sample of participants (N = 563). RESULTS: The reliability of the screening question was good (kappa value 0.63, 95% confidence interval [CI] 0.53-0.73). In HUNT 3, 48% had chronic MSCs and 20% had chronic widespread MSCs. The age-adjusted prevalence of chronic MSCs was higher (P < 0.001) in HUNT 3 (47.9%, 95% CI 47.6-48.2) compared with HUNT 2 (44.8%, 95% CI 44.5-45.2), evident for both genders, and most prominent in the age group 20-29 years. Chronic widespread MSCs were more common in HUNT 3 than in HUNT 2 among women (28.2 vs 26.0%, P < 0.001). Increased prevalence during the 11-year period was also found in supplementary analyses evaluating the influence of differences in participation rate. CONCLUSIONS: The prevalence of chronic MSCs and chronic widespread MSCs is high. The prevalence of chronic MSCs increased during the 11-year period. A nonresponse bias interfering with the comparisons over time could not completely be ruled out.

The association between selected genetic variants and individual differences in experimental pain.

OBJECTIVES: The underlying mechanisms for individual differences in experimental pain are not fully understood, but genetic susceptibility is hypothesized to explain some of these differences. In the present study we focus on three genetic variants important for modulating experimental pain related to serotonin (SLC6A4 5-HTTLPR/rs25531 A>G), catecholamine (COMT rs4680 Val158Met) and opioid (OPRM1 rs1799971 A118G) signaling. We aimed to investigate associations between each of the selected genetic variants and individual differences in experimental pain. METHODS: In total 356 subjects (232 low back pain patients and 124 healthy volunteers) were genotyped and assessed with tests of heat pain threshold, pressure pain thresholds, heat pain tolerance, conditioned pain modulation (CPM), offset analgesia, temporal summation and secondary hyperalgesia. Low back pain patients and healthy volunteers did not differ in regards to experimental test results or allelic frequencies, and were therefore analyzed as one group. The associations were tested using analysis of variance and the Kruskal-Wallis test. RESULTS: No significant associations were observed between the genetic variants (SLC6A4 5-HTTLPR/rs25531 A>G, COMT rs4680 Val158Met and OPRM1 rs1799971 A118G) and individual differences in experimental pain (heat pain threshold, pressure pain threshold, heat pain tolerance, CPM, offset analgesia, temporal summation and secondary hyperalgesia). CONCLUSIONS: The selected pain-associated genetic variants were not associated with individual differences in experimental pain. Genetic variants well known for playing central roles in pain perception failed to explain individual differences in experimental pain in 356 subjects. The finding is an important contribution to the literature, which often consists of studies with lower sample size and one or few experimental pain assessments.

Low Back Pain With Persistent Radiculopathy; the Clinical Role of Genetic Variants in the Genes SOX5, CCDC26/GSDMC and DCC.

In a recently published genome-wide association study (GWAS) chronic back pain was associated with three loci; SOX5, CCDC26/GSDMC and DCC. This GWAS was based on a heterogeneous sample of back pain disorders, and it is unknown whether these loci are of clinical relevance for low back pain (LBP) with persistent radiculopathy. Thus, we examine if LBP with radiculopathy 12 months after an acute episode of LBP with radiculopathy is associated with the selected single nucleotide polymorphisms (SNPs); SOX5 rs34616559, CCDC26/GSDMC rs7833174 and DCC rs4384683. In this prospective cohort study, subjects admitted to a secondary health care institution due to an acute episode of LBP with radiculopathy, reported back pain, leg pain, and Oswestry Disability Index (ODI), were genotyped and followed up at 12 months (n = 338). Kruskal-Wallis H test showed no association between the SNPs and back pain, leg pain or ODI. In conclusion, LBP with radiculopathy 12 months after an acute episode of LBP with radiculopathy, is not associated with the selected SNPs; SOX5 rs34616559, CCDC26/GSDMC rs7833174 and DCC rs4384683. This absent or weak association suggests that the SNPs previously associated with chronic back pain are not useful as prognostic biomarkers for LBP with persistent radiculopathy.

Associations between serum lipid levels and chronic low back pain.

BACKGROUND: Low back pain may be related to abnormal lipid levels because of atherosclerosis in arteries supplying the lumbar region. METHODS: In the cross-sectional HUNT 2 study in the Norwegian county of Nord-Trøndelag, lipid levels were measured in 33,962 women and 30,031 men. A total of 8954 women (26%) and 6273 men (21%) reported suffering from low back pain continuously for at least 3 months in the past year. RESULTS: In age-adjusted analyses, the prevalence of low back pain was inversely associated with HDL cholesterol and positively associated with triglycerides, with stronger associations in women than in men. Relatively weak associations remained in women after adjustment for smoking, physical activity, education, work status, blood pressure, and body mass, but no associations remained among men. Total cholesterol levels were unrelated to low back pain in either sex after age adjustment. CONCLUSIONS: The results are partly consistent with the atherosclerosis hypothesis.

Obesity in Young Adulthood: The Role of Physical Activity Level, Musculoskeletal Pain, and Psychological Distress in Adolescence (The HUNT-Study).

The global obesity epidemic raises long-term health concerns which underline the importance of preventive efforts. We aimed to investigate individual and combined effects of common health problems in adolescence on the probability of obesity in young adulthood. This prospective population-based study included data from participants in the Nord-Trøndelag Health Study in Norway (Young-HUNT1 (1995-1997), age 13-19, baseline) who participated in HUNT3 as young adults 11 years later (age 23-31). Exposure variables at baseline included self-reported physical activity, musculoskeletal pain, and psychological distress. We examined associations between exposure variables and the main outcome of obesity in young adulthood (BMI ≥ 30 kg/m2) using univariate and multiple logistic regression, stratified by sex. Probabilities of obesity for given combinations of the exposure variables were visualized in risk matrixes. The study sample consisted of 1859 participants (43.6% boys). Higher probabilities of obesity in young adulthood were found across combinations of lower physical activity levels and presence of musculoskeletal pain in adolescence. Additional adverse effects of psychological distress were low. Proactive intervention strategies to promote physical activity and facilitate sports participation for all adolescents, whilst addressing musculoskeletal pain and its potential individual causes, could prove helpful to prevent development of obesity in young adulthood.

Does diabetes influence the probability of experiencing chronic low back pain? A population-based cohort study: the Nord-Trøndelag Health Study.

OBJECTIVE: Low back pain (LBP) is a major problem in modern society and it is important to study possible risk factors for this disorder. People with diabetes are often affected by LBP, but whether diabetes represents a risk factor for LBP has not been studied in detail. The aim of this study was to explore the association between diabetes and subsequent risk of chronic LBP. DESIGN: An 11-year follow-up study. SETTING: The Nord-Trøndelag Health Study (HUNT2; 1995-1997) and HUNT3 (2006-2008) surveys of Nord-Trøndelag County in Norway. MAIN OUTCOME MEASURE: Chronic LBP, defined as LBP persisting at least 3 months continuously during the last year. PARTICIPANTS: A total of 18 972 persons without chronic LBP at baseline in HUNT2, and 6802 persons who reported chronic LBP at baseline in HUNT2. METHODS: Associations between diabetes and risk of chronic LBP among individuals aged 30-69 years were examined by generalised linear modelling. RESULTS: Men without chronic LBP at baseline showed a significant association between diabetes and risk of chronic LBP (relative risk (RR) 1.43, 95% CI 1.04 to 1.96, p=0.043). In women, no association was found (RR 1.01, 95% CI 0.69 to 1.48, p=0.98). No association could be established between diabetes and recurrence or persistence of chronic LBP after 11 years in either sex. CONCLUSIONS: Men with a diagnosis of diabetes may have a higher risk of subsequently experiencing chronic LBP.

Predicting the outcome of persistent sciatica using conditioned pain modulation: 1-year results from a prospective cohort study.

Background and aims Recovery in patients hospitalised with severe sciatica is unpredictable. Prognostic tools to aid clinicians in the early identification of patients at risk of developing chronic sciatic pain are warranted. Conditioned pain modulation (CPM) is a psychophysical measure of the endogenous pain modulatory pathways. Several studies have suggested CPM as a potentially important predictive biomarker for the development of chronic pain. The aim of the study was to determine whether CPM effect in patients still suffering from leg pain 6 weeks after hospital discharge for severe sciatica is associated with persistent leg pain at 12 months. A potential association would suggest that measuring CPM effect could be a valuable prognostic tool in the hospital management of sciatica. Methods A prospective cohort study in which CPM effect was measured 6 weeks after hospital discharge following an acute admission with sciatica as the main complaint. The impact of CPM effect on the outcome was analysed using logistic regression. The outcome measured was self-reported leg pain score of ≥1 in the past week on a 0-10 numeric rating scale (NRS) at 12 months post discharge. Results A total of 111 patients completed the entire study, 51 of whom received non-randomised surgical treatment. Crude and confounder adjusted analyses showed no significant association between CPM effect and leg-pain measured at 12 months, crude Odds Ratio 0.87, 95% CI 0.7-1.1, p = 0.23. Conclusions Our results suggest that CPM assessment has limited prognostic value for the long-term outcome in severe sciatica when measured 6 weeks after hospital discharge. Implications The present study adds important knowledge concerning the limited clinical use of late CPM testing in sciatica patients. The heterogeneity in patients, the wide range of treatments received and a generally favourable outcome are factors that may affect CPM's clinical value as a prognostic factor for severe sciatica.

The association between insomnia, c-reactive protein, and chronic low back pain: cross-sectional analysis of the HUNT study, Norway.

BACKGROUND AND AIMS: Chronic low back pain (chronic LBP) is the number one cause for years lived with disability among 301 diseases and injuries analyzed by The Global Burden of Disease study 2013. Insomnia is highly prevalent among people with chronic LBP. To explain the sleep-pain relationship, theoretical models propose that insomnia symptoms may be associated with increased basal inflammation, operationalized as c-reactive protein (CRP) and lead to further pain and disrupted sleep. We aimed to determine the associations between insomnia, chronic LBP, and inflammation (operationalized as CRP), whilst controlling for age, body mass index, smoking, physical activity, depression, anxiety and osteoarthritis. METHODS: A cross-sectional analysis of the third Nord-Trøndelag Health Study (2006-2008), a rural population survey of 50,666 participants in Norway aged 20-96 years. Insomnia (dichotomous) was defined according to the Diagnostic and Statistical Manual of Mental Disorders 5th Edition, and chronic LBP (dichotomous) as low back pain or stiffness lasting at least 3 months. Data for CRP were obtained from non-fasting serum samples and assessed via latex immunoassay methodology. We excluded participants with the following self-reported chronic somatic diseases: chronic heart failure, chronic obstructive pulmonary disease, rheumatoid arthritis, fibromyalgia or ankylosing spondylosis. Possible associations between presence of insomnia and presence of chronic LBP (dependent), and the level of CRP and presence of chronic LBP (dependent), were assessed using logistic regression models. The possible association between insomnia and CRP (dependent) was assessed using linear regression. Multivariable analyses were conducted adjusting for confounders stated in our aim that achieved p ≤ 0.2 in univariate regressions. We performed stratified analyses for participants with "Normal" (<3 mg/L) "Elevated" (3-10 mg/L) and "Very High" (>10 mg/L) levels of CRP. RESULTS: In our total included sample (n = 30,669, median age 52.6, 54% female), 6.1% had insomnia (n = 1,871), 21.4% had chronic LBP (n = 6,559), and 2.4% had both (n = 719). Twenty four thousand two hundred eighty-eight (79%) participants had "Normal" CRP, 5,275 (17%) had "Elevated" CRP, and 1,136 (4%) had "Very High" CRP. For participants with "Normal" levels of CRP, insomnia was associated with higher levels of CRP (adjusted B = 0.04, 95%CI [0.00-0.08], p = 0.046), but not for people with "Elevated" or "Very High" levels of CRP. There was an association between CRP and presence of chronic LBP in the total sample (adjusted OR = 1.01, [1.00-1.01], p = 0.013) and for people with "Normal" CRP (1.05, [1.00-1.10, p = 0.034]. Insomnia was associated with the presence of chronic LBP in the total sample (adjusted OR = 1.99, 95%CI [1.79-2.21], <0.001) and for people with "Normal", "Elevated" and "Very High". CONCLUSIONS: Individuals with insomnia have twice the odds of reporting chronic LBP. Insomnia, CRP and chronic LBP appear to be linked but the role of CRP appears to be limited. Longitudinal studies may help further explore the causal inference between insomnia chronic LBP, and inflammation. IMPLICATIONS: Given the strong relationship between insomnia and chronic LBP, screening and management of comorbid insomnia and chronic LBP should be considered in clinical practice. Further longitudinal studies are required to explore whether the presence of insomnia and increased inflammation affects the development of chronic LBP.

Is chronic low back pain a risk factor for diabetes? The Nord-Trøndelag Health Study.

OBJECTIVE: The purpose of this study was to examine the risk of diabetes associated with the presence or absence of chronic low back pain, considering both cross-sectional and cohort data. RESEARCH DESIGN AND METHODS: Analyses were based on the Norwegian HUNT2 and HUNT3 surveys of Nord-Trøndelag County. The prevalence of diabetes was compared in groups with and without chronic low back pain among 45 157 participants aged 30-69 years. Associations between low back pain at baseline and risk of diabetes were examined in an 11-year follow-up of 30 380 individuals with no baseline diagnosis of diabetes. The comorbidity between diabetes and low back pain was assessed at the end of follow-up. All analyses were carried out considering generalized linear models incorporating adjustment for other relevant risk factors. RESULTS: Cross-sectional analyses did not reveal any association between low back pain and diabetes. With adjustment for age, body mass index, physical activity and smoking, the cohort study of women showed a significant association between low back pain at baseline and risk of diabetes (RR 1.30; 95% CI 1.09 to 1.54, p=0.003). The association differed between age groups (p=0.015), with a stronger association in relatively young women. In men, no association was found in the whole age range (RR 1.02; 95% CI 0.86 to 1.21, p=0.82). No association was observed between diabetes and chronic low back pain at the end of follow-up. CONCLUSION: Among younger women, those with chronic low back pain may have an increased risk of diabetes.

Do incident musculoskeletal complaints influence mortality? The Nord-Trøndelag Health study.

BACKGROUND: Musculoskeletal complaints (MSC) are common in the general population, causing a major disease burden to the individual and society. The association between MSC and mortality is still unclear. To our knowledge, no study has hitherto evaluated the association between MSC onset within the last month (incident MSC) on the one hand, and all-cause and cause-specific mortality on the other. METHODS: This prospective population-based cohort study was done using data from the second Nord-Trøndelag Health Study (HUNT2) linked with data from a comprehensive national registry of cause of death. A total of 25,931 participants at risk for incident MSC were included. Hazard ratios (HR) of mortality were estimated for participants with incident MSC using Cox regression based on a mean of 14.1 years of follow-up. RESULTS: Participants who reported incident MSC did not have an excess mortality compared to those with no MSC in the analyses of all-cause mortality (HR 0.99, 95% CI 0.89-1.10) and cause specific mortality. This was true also after adjustment for several potential confounding factors. No clear association between the number of MSC body sites and mortality was found. CONCLUSION: Incident MSC were not associated with an increased mortality, neither for all-cause mortality, nor cause-specific mortality.

The Mortality Associated With Chronic Widespread Musculoskeletal Complaints: A Systematic Review of the Literature.

BACKGROUND: Chronic widespread musculoskeletal complaints (CWMSC) are a prevalent condition with a large impact on quality of life and with a large burden on society. Studies investigating the relationship between CWMSC and mortality have yielded inconsistent results. The present study aimed to clarify this relationship through a systematic review of the existing literature, including meta-analyses, to estimate pooled results and heterogeneity. METHODS: The MEDLINE, EMBASE and Science Citation Index Expanded databases were searched in February 2016. Broad search terms were used to identify as many observational studies as possible that investigated the association between CWMSC and mortality. The identified studies were evaluated according to predetermined inclusion criteria. RESULTS: Six studies fulfilled the inclusion criteria. In pooled unadjusted analyses of three studies evaluating CWMSC, a non-significant tendency of increased overall mortality was found [mortality risk ratio (MRR) 1.69, 95% confidence interval (CI) 0.91-3.14]. However, in pooled analyses of all six studies reporting adjusted results, the non-significant tendency for higher mortality rates in those with CWMSC was nearly eliminated (MRR 1.13, 95% CI 0.95-1.34). Heterogeneity between studies was moderate to high, particularly regarding the use of confounding factors. CONCLUSIONS: In this systematic review, based on a limited number of studies, pooled data gave no evidence of a higher mortality rate among individuals with CWMSC. The non-significant tendency for a higher mortality rate in unadjusted pooled analyses was nearly eliminated in the adjusted pooled analyses, considering lifestyle factors such as physical activity smoking. In population-based studies evaluating the relationship between CWMSC and mortality rates, we recommend that both unadjusted and adjusted analyses should be presented. Copyright © 2016 John Wiley & Sons, Ltd.

Physical activity level at work and risk of chronic low back pain: A follow-up in the Nord-Trøndelag Health Study.

BACKGROUND: Physical activity in leisure time seems to reduce the risk of low back pain, but it is not known whether occupational activity, as recorded in a representative working population, produces a higher or lower risk. OBJECTIVE: To study associations between physical activity level at work and risk of chronic low back pain. METHODS: Associations were examined in a Norwegian prospective study using data from the HUNT2 and HUNT3 surveys carried out in the whole county of Nord-Trøndelag. Participants were 7580 women and 7335 men who supplied information about physical activity level at work. Levels considered were sedentary work, work involving walking but no heavy lifting, work involving walking and heavy lifting, and particularly strenuous physical work. Nobody in the cohort was affected by chronic low back pain at baseline. After 11 years, participants reported whether they suffered from chronic low back pain. Generalized linear modelling with adjustment for potential confounders was applied to assess associations with risk factors. RESULTS: In age-adjusted analyses both women and men showed statistically significant associations between physical activity at work and risk of chronic low back pain, suggesting positive relationships. For particularly strenuous physical work the relative risk of chronic low back pain was 1.30 (95% CI: 1.00-1.71) in women and 1.36 (95% CI 1.17-1.59) in men, compared to sedentary work. Women still showed a general association with activity level after adjustment for education, leisure time physical activity, BMI, smoking and occupational category. In men, the higher risk was only maintained for particularly strenuous work. CONCLUSION: In this cohort, women had a higher risk of chronic low back pain with work involving walking and heavy lifting or particularly strenuous work, compared to sedentary work. Men participating in particularly strenuous work also experienced a higher risk of chronic low back pain.

Is there an association between vitamin D status and risk of chronic low back pain? A nested case-control analysis in the Nord-Trøndelag Health Study.

OBJECTIVES: To explore potential associations between vitamin D status and risk of chronic low back pain (LBP) in a Norwegian cohort, and to investigate whether relationships depend on the season of blood sample collection. DESIGN: A nested case-control study in a prospective data set. SETTING: The Norwegian community-based Nord-Trøndelag Health Study (HUNT). Data were collected in the HUNT2 (1995-1997) and HUNT3 (2006-2008) surveys. MAIN OUTCOME MEASURE: Chronic LBP, defined as LBP persisting at least 3 months continuously during the past year. PARTICIPANTS: Among individuals aged 19-55 years without LBP in HUNT2, a data set was generated including 1685 cases with LBP in HUNT3 and 3137 controls without LBP. METHODS: Blood samples from the participants collected in HUNT2 were analysed for serum 25-hydroxyvitamin D (25(OH)D) level. Associations with LBP in HUNT3 were evaluated by unconditional logistic regression analysis with adjustment for age, sex, work status, physical activity at work and in leisure time, education, smoking, and body mass index. RESULTS: No association between vitamin D status and risk of chronic LBP was found in the total data set (OR per 10 nmol/L 25(OH)D=1.01, 95% CI 0.97 to 1.06) or in individuals with blood samples collected in summer/autumn (OR per 10 nmol/L 25(OH)D=0.99, 95% CI 0.93 to 1.06). For blood samples drawn in winter/spring, associations differed significantly between women and men (p=0.004). Among women a positive association was seen (OR per 10 nmol/L 25(OH)D=1.11, 95% CI 1.02 to 1.20), but among men no significant association was observed (OR per 10 nmol/L 25(OH)D=0.90, 95% CI 0.81 to 1.01). CONCLUSIONS: Overall, no association between vitamin D status and risk of LBP was demonstrated. The association suggested in women for the winter/spring season cannot be regarded as established.