Longitudinal changes of serum cytokines in patients with chronic low back pain and Modic changes.

OBJECTIVES: To explore serum cytokine levels over time in patients with chronic low back pain (cLBP) and Modic changes (MCs), difference in change between treatment groups in the Antibiotics in Modic Changes (AIM) study and associations between change in cytokines and low back pain. METHODS: Serum concentrations of 39 cytokines were measured at baseline and 1 year from 73 participants in the AIM study; 30 randomized to placebo, 43 to Amoxicillin. Low back pain intensity was measured by numeric rating scale. Change in cytokine levels over time were assessed by paired t-tests. Difference in change in cytokine levels between treatment groups and associations between changes in LBP and cytokine levels were assessed by linear regression models. Networks of cytokine changes in each treatment groups were explored by Pearson's correlations. RESULTS: Five cytokines changed from baseline to 1 year, (mean change, log transformed values with CI) C-X-C motif chemokine ligand (CXCL) 10 (IP-10) (0.11 (0.01-0.20)), CXCL13 (0.61 (0.00-0.12)), C-C motif chemokine ligand (CCL)26 (0.05 (0.01-0.1)), granulocyte macrophage-colony stimulating factor (GM-CSF) (-0.12 (-0.23 to 0.00)) and CXCL11 (0.12 (0.03-0.22)). Treatment group only influenced change in CCL21 (ß 0.07 (0.01-0.12)), and IL-6 (ß -0.17 (-0.30 to -0.03)). Change in CXCL13 (ß 2.43 (0.49-4.38)), CCL27 (ß 3.07 (0.46-5.69)), IL-8 (ß 1.83 (0.08-3.58)) and CCL19 (ß 3.10 (0.86-5.43)) were associated with change in LBP. The correlation networks of cytokine changes demonstrate small differences between treatment groups. CONCLUSIONS: Cytokine levels are relatively stable over time in our sample, with little difference between treatment groups. Some cytokines may be associated with LBP intensity. The differences between the correlation networks suggest that long-term Amoxicillin-treatment may have longstanding effects to be further explored.

Influence of ergonomic factors on peripheral neuropathy under HAV exposure.

BACKGROUND: Hand-arm vibration (HAV) is a risk factor for carpal tunnel syndrome (CTS) and ulnar neuropathy at the elbow (UNE). It is unclear how ergonomic factors influence the relationship between HAV exposure and CTS and UNE. AIMS: We aimed to assess the relationship between cumulative HAV exposure and CTS and UNE in workers exposed to HAV from two tools with different ergonomic profiles. METHODS: We performed nerve conduction studies (NCSs) of the sensory and motor median and ulnar nerves and recorded symptoms indicating CTS and UNE in workers exposed to HAV from impact wrenches or from rock drills. Exposure was measured as cumulative lifetime exposure. We used linear regression adjusted for age and body mass index to assess linear relationships. RESULTS: Sixty-five workers participated (33 rock drill and 32 impact wrench operators). We found inverse linear associations between cumulative HAV exposure and median nerve sensory conduction velocity in impact wrench operators and ulnar nerve motor conduction velocity in rock drill operators (beta of 0.63 and 0.75). Based on NCS findings and symptoms, seven impact wrench operators had CTS and one UNE, and four rock drill operators had CTS and six UNE. CONCLUSIONS: Our findings indicate that ergonomic factors influence the development of CTS and UNE under HAV exposure. The ergonomic profile seems to influence which type of neuropathy workers exposed to HAV will develop. Design of occupational exposure guidelines and future studies should be based on ergonomic profile and exposure characteristics for different tools and not merely HAV.

Development and validation of a prediction model for incident hand osteoarthritis in the HUNT study.

OBJECTIVE: To develop and externally validate prediction models for incident hand osteoarthritis (OA) in a large population-based cohort of middle aged and older men and women. DESIGN: We included 17,153 men and 18,682 women from a population-based cohort, aged 35-70 years at baseline (1995-1997). Incident hand OA were obtained from diagnostic codes in the Norwegian National Patient Register (1995-2018). We studied whether a range of self-reported and clinically measured predictors could predict hand OA, using the Area Under the receiver-operating Curve (AUC) from logistic regression. External validation of an existing prediction model for male hand OA was tested on discrimination in a sample of men. Bootstrapping was used to avoid overfitting. RESULTS: The model for men showed modest discriminatory ability (AUC = 0.67, 95% CI 0.62-0.71). Adding a genetic risk score did not improve prediction. Similar discrimination was observed in the model for women (AUC = 0.62, 95% CI 0.59-0.64). Prediction was not improved by adding a genetic risk score or hormonal and reproductive factors. Applying external validation, similar results were observed among men in HUNT (The Nord-Trøndelag Health Study) as in the developmental sample (AUC = 0.62, 95% CI 0.57-0.65). CONCLUSION: We developed prediction models for incident hand OA in men and women. For women, the model included body mass index (BMI), heavy physical work, high physical activity and perceived poor health. The model showed moderate discrimination. For men, we have shown that a prediction model including BMI, education and information on sleep can predict incident hand OA in several populations with moderate discriminative ability.

The causal role of smoking on the risk of headache. A Mendelian randomization analysis in the HUNT study.

BACKGROUND AND PURPOSE: Headache has been associated with various lifestyle and psychosocial factors, one of which is smoking. The aim of the present study was to investigate whether the association between smoking intensity and headache is likely to be causal. METHOD: A total of 58 316 participants from the Nord-Trøndelag Health (HUNT) study with information on headache status were genotyped for the rs1051730 C>T single-nucleotide polymorphism (SNP). The SNP was used as an instrument for smoking intensity in a Mendelian randomization analysis. The association between rs1051730 T alleles and headache was estimated by odds ratios with 95% confidence intervals. Additionally, the association between the SNP and migraine or non-migrainous headache versus no headache was investigated. All analyses were adjusted for age and sex. RESULTS: There was no strong evidence that the rs1051730 T allele was associated with headache in ever smokers (odds ratio 0.99, 95% confidence interval 0.95-1.02). Similarly, there was no association between the rs1051730 T allele and migraine or non-migrainous headache versus no headache. CONCLUSION: The findings from this study do not support that there is a strong causal relationship between smoking intensity and any type of headache. Larger Mendelian randomization studies are required to examine whether higher smoking quantity can lead to a moderate increase in the risk of headache subtypes.

Effects of spatial fMRI resolution on the classification of naturalistic movies.

Studies involving multivariate pattern analysis (MVPA) of BOLD fMRI data generally attribute the success of the information-theoretic approach to BOLD signal contrast on the fine spatial scale of millimeters facilitating the classification or decoding of perceptual stimuli. However, to date MVPA studies that have actually explored fMRI resolutions at less than 2 mm voxel size are rare and limited to small sets of unnatural stimuli (like visual gratings) as well as specific sub-regions of the brain, notably the primary somatosensory cortices. To investigate what spatial scale best supports high information extraction under more general conditions this study combined naturalistic movie stimuli with high-resolution fMRI at 7 T and linear discriminant analysis (LDA) of global and local BOLD signal patterns. Contrary to predictions, LDA and similar classifiers reached a maximum in classification accuracy (CA) at a smoothed resolution close to 3 mm, well above the 1.2 mm voxel size of the fMRI acquisition. Maximal CAs around 90% were contingent upon global fMRI signal patterns comprising 4 k-16 k of the most reactive voxels distributed sparsely throughout the occipital and ventro-temporal cortices. A Searchlight analysis of local fMRI patterns largely confirmed the global results, but also revealed a small subset of brain regions in early visual cortex showing limited increases in CA with higher resolution. Principal component analysis of the global and local fMRI signal patterns suggested that reproducible neuronal contributions were spatially auto-correlated and smooth, while other components of higher spatial frequency were likely related to physiological noise and responsible for the reduced CA at higher resolution. Systematic differences between experiments and subjects suggested that higher CA was significantly correlated with more consistent behavior revealed by eye tracking. Thus, the optimal resolution of fMRI data for MVPA was mainly limited by physiological noise of high spatial frequency as well as behavioral (in-)consistency.

Age of menarche is associated with knee joint replacement due to primary osteoarthritis (The HUNT Study and the Norwegian Arthroplasty Register).

OBJECTIVE: To investigate whether parity, age at menarche, menopausal status, age at menopause, use of oral contraceptives (OC) or use of hormone replacement therapy (HRT) were associated with total knee replacement (TKR) or total hip replacement (THR) due to primary osteoarthritis. METHOD: In a prospective cohort study of 30,289 women from the second and third surveys of the Nord-Trøndelag Health Study, data were linked to the Norwegian Arthroplasty Register (NAR) in order to identify TKR or THR due to primary osteoarthritis. Cox proportional hazards models were used to estimate the hazard ratios (HRs). RESULTS: We observed 430 TKRs and 675 THRs during a mean follow-up time of 8.3 years. Increasing age at menarche was inversely associated with the risk of TKR (P-trend < 0.001). Past users and users of systemic HRT were at higher risk of TKR compared to never users (HR 1.42 (95% confidence interval (CI) 1.06-1.90) and HR 1.40 (95% CI 1.03-1.90), respectively). No association was found between parity, age at menarche, menopausal status, age at menopause, oral contraceptive use or HRT use and THR. CONCLUSION: We found that increasing age at menarche reduced the risk of TKR. Past users and users of systemic HRT were at higher risk of TKR compared to never users. Parity did not increase the risk of THR or TKR.

The causal role of smoking on the risk of hip or knee replacement due to primary osteoarthritis: a Mendelian randomisation analysis of the HUNT study.

OBJECTIVE: Smoking has been associated with a reduced risk of hip and knee osteoarthritis (OA) and subsequent joint replacement. The aim of the present study was to assess whether the observed association is likely to be causal. METHOD: 55,745 participants of a population-based cohort were genotyped for the rs1051730 C > T single-nucleotide polymorphism (SNP), a proxy for smoking quantity among smokers. A Mendelian randomization analysis was performed using rs1051730 as an instrument to evaluate the causal role of smoking on the risk of hip or knee replacement (combined as total joint replacement (TJR)). Association between rs1051730 T alleles and TJR was estimated by hazard ratios (HRs) and 95% confidence intervals (CIs). All analyses were adjusted for age and sex. RESULTS: Smoking quantity (no. of cigarettes) was inversely associated with TJR (HR 0.97, 95% CI 0.97-0.98). In the Mendelian randomization analysis, rs1051730 T alleles were associated with reduced risk of TJR among current smokers (HR 0.84, 95% CI 0.76-0.98, per T allele), however we found no evidence of association among former (HR 0.97, 95% CI 0.88-1.07) and never smokers (HR 0.97, 95% CI 0.89-1.06). Neither adjusting for body mass index (BMI), cardiovascular disease (CVD) nor accounting for the competing risk of mortality substantially changed the results. CONCLUSION: This study suggests that smoking may be causally associated with the reduced risk of TJR. Our findings add support to the inverse association found in previous observational studies. More research is needed to further elucidate the underlying mechanisms of this causal association.

Candidate-gene association study searching for genetic factors involved in migraine chronification.

INTRODUCTION: Chronic migraine (CM) is at the severe end of the clinical migraine spectrum, but its genetic background is unknown. Our study searched for evidence that genetic factors are involved in the chronification process. METHODS: We initially selected 144 single-nucleotide polymorphisms (SNPs) from 48 candidate genes, which we tested for association in two stages: The first stage encompassed 262 CM patients, the second investigated 226 patients with high-frequency migraine (HFM). Subsequently, SNPs with p values < 0.05 were forwarded to the replication stage containing 531 patients with CM or HFM. RESULTS: Eight SNPs were significantly associated with CM and HFM in the two-stage phase. None survived replication in the third stage. DISCUSSION: We present the first comprehensive genetic association study for migraine chronification. There were no significant findings. Future studies may benefit from larger, genome-wide data sets or should use other genetic approaches to identify genetic factors involved in migraine chronification.

Blood pressure as a risk factor for headache and migraine: a prospective population-based study.

BACKGROUND AND PURPOSE: During the past decade, several population-based studies have found an inverse association between blood pressure (BP) and headache. However, most of them have a cross-sectional design or lack a validated definition of a headache-free population at baseline. Therefore, additional population-based studies using a clearly defined headache-free population and a prospective design are warranted. METHODS: Data from two large epidemiological studies, the Nord-Trondelag Health Survey 1995-1997 (HUNT 2) and 2006-2008 (HUNT 3), were used to evaluate the association between BP (systolic, diastolic and pulse pressure) at baseline and headache (migraine and tension type headache) at follow-up. RESULTS: An inverse relationship was found between all three BP measures at baseline in HUNT 2 and any headache in HUNT 3, more evident for systolic BP [odds ratio (OR) 0.90 per 10 mmHg increase in systolic BP, 95% confidence interval (CI) 0.87-0.93, P < 0.001] and pulse pressure (OR 0.84 per 10 mmHg increase in pulse pressure, 95% CI 0.80-0.89, P < 0.001) than for diastolic BP (OR 0.92 per 10 mmHg increase in diastolic BP, 95% CI 0.87-1.00, P = 0.036). The most robust finding, evident for both sexes, was that increased pulse pressure was linked to decreased prevalence of both migraine and tension type headache. CONCLUSION: An inverse relationship between BP and subsequent development of headache was confirmed in this large-scale population-based cohort study. Nevertheless, further research is needed to investigate the underlying mechanisms explaining these findings.

The Neck Disability Index (NDI) and its correlation with quality of life and mental health measures among patients with single-level cervical disc disease scheduled for surgery.

BACKGROUND: The Neck Disability Index (NDI) is widely used as a self-rated disability score in patients with cervical radiculopathy. The purpose of this study was to evaluate whether the NDI score correlated with other assessments of quality of life and mental health in a specific group of patients with single-level cervical disc disease and corresponding radiculopathy. METHODS: One hundred thirty-six patients were included in a prospective, randomized controlled clinical multicenter study on one-level anterior cervical discectomy with arthroplasty (ACDA) versus one-level anterior cervical discectomy with fusion (ACDF). The preoperative data were obtained at hospital admission 1 to 3 days prior to surgery. The NDI score was used as the dependent variable and correlation as well as regression analyses were conducted to assess the relationship with the short form-36, EuroQol-5Dimension-3 level and Hospital Anxiety and Depression Scale. RESULTS: The mean age at inclusion was 44.1 years (SD ±7.0, range 26-59 years), of which 46.3 % were male. Mean NDI score was 48.6 (SD = 12.3, minimum 30 and maximum 88). Simple linear regression analysis demonstrated a significant correlation between NDI and the EuroQol-5Dimension-3 level [R = -0.64, 95 % confidence interval (CI) -30.1- -19.8, p < 0.001] and to a lesser extent between NDI and the short form-36 physical component summary [R = -0.49, 95 % CI (-1.10- -0.58), p < 0.001] and the short form-36 mental component summary [R = -0.25, 95 % CI (-0.47- -0-09), p = 0.004]. Regarding NDI and the Hospital Anxiety and Depression Scale, a significant correlation for depression was found [R = 0.26, 95 % CI (0.21-1.73), p = 0.01]. Multiple linear regression analysis showed a statistically significant and the strongest correlation between NDI and the independent variables in the following order: EuroQol-5Dimension-3 level [R = -0.64, 95 % CI (-23.5- -7.9), p <0.001], short form-36 physical component summary [R = -0.41, 95 % CI (-0.93- -0.23), p = 0.001] and short form-36 mental component summary [R = -0.36, 95 % CI (-0.53- -0.15), p = 0.001]. CONCLUSION: The results from the present study show that the NDI correlated significantly with a different quality of life and mental health measures among patients with single-level cervical disc disease and corresponding radiculopathy.

Body mass index and the risk of meningioma, glioma and schwannoma in a large prospective cohort study (The HUNT Study).

BACKGROUND: Obesity increases the risk for a number of solid malignant tumours. However, it is not clear whether body mass index (BMI) and height are associated with the risk of primary tumours of the central nervous system (CNS). METHODS: In a large population study (The Nord-Trøndelag Health Study (HUNT Study)) of 74 242 participants in Norway, weight and height were measured. During follow-up, incident CNS tumours were identified by individual linkage to the Norwegian Cancer Registry. Sex- and age-adjusted and multivariable Cox regression analyses were used to evaluate BMI and height in relation to the risk of meningioma, glioma and schwannoma. RESULTS: A total of 138 meningiomas, 148 gliomas and 39 schwannomas occurred during 23.5 years (median, range 0-25) of follow-up. In obese women (BMI ≥ 30 kg m(-2)), meningioma risk was 67% higher (hazard ratio (HR)=1.68, 95% confidence interval (CI): 0.97-2.92, P-trend=0.05) than in the reference group (BMI 20-24.9 kg m(-2)), whereas no association with obesity was observed in males. There was no association of BMI with glioma risk, but there was a negative association of overweight/obesity (BMI ≥ 25 kg m(-2)) with the risk of schwannoma (HR=0.48, 95% CI: 0.23-0.99). However, the schwannoma analysis was based on small numbers. Height was not associated with the risk for any tumour subgroup. CONCLUSION: These results suggest that BMI is positively associated with meningioma risk in women, and possibly, inversely associated with schwannoma risk.

The bidirectional relationship between headache and chronic musculoskeletal complaints: an 11-year follow-up in the Nord-Trøndelag Health Study (HUNT).

BACKGROUND AND PURPOSE: Chronic daily headache (CDH) and chronic musculoskeletal complaints (CMSCs) are associated disorders, but whether there is a causal relationship between them is unclear. OBJECTIVE: To determine whether CMSCs are associated with the subsequent development of CDH and vice versa. METHODS: This longitudinal population-based cohort study used data from two consecutive surveys in the Nord-Trøndelag Health Study (HUNT 2 and 3) performed in 1995-1997 and 2006-2008. Amongst the 51 383 participants aged ≥ 20 years at baseline, 41 766 were eligible approximately 11 years later. Of these, 26 197 (63%) completed the questions regarding headache and CMSCs in HUNT 3. RESULTS: A bidirectional relationship was found between headache and CMSCs. In the multivariate analyses adjusting for known potential confounders, a nearly two fold risk (OR 1.8; 95% CI 1.5-2.3) for developing CDH was found for those with CMSCs at baseline. Vice versa, a similarly elevated risk of CMSCs (OR 1.8; 95% CI 1.2-2.6), and even higher risk of chronic widespread MSCs (OR 2.7; 95% CI 1.6-4.7), was found at follow-up amongst those with CDH at baseline. CONCLUSION: CMSCs predispose to CDH and CDH predisposes to CMSCs 11 years later. This may have relevance to understanding the pathophysiology of these disorders. CMSCs should be treated not only to relieve them but also to prevent the development of CDH, and vice versa.

Migrainous infarction: a Nordic multicenter study.

BACKGROUND AND PURPOSE: Migrainous infarction (MI), i.e., an ischemic stroke developing during an attack of migraine with aura is rare and the knowledge of its clinical characteristics is limited. Previous case series using the International Classification of Headache Disorders (ICHD) included <10 cases which make conclusions less valid. This study aimed to describe characteristics and outcome of MI in a larger sample. METHODS: We analyzed demographic data, risk factors, migraine medication, stroke localization, symptoms, and outcome in a sample of 33 patients with MI according to second edition of the ICHD criteria collected from seven Nordic headache clinics. RESULTS: Amongst 33 patients with MI, there were 20 (61%) women and 13 (39%) men with the median age for stroke of 39 (range 19-76) years. Traditional risk factors for stroke were rare compared with Scandinavian young ischemic stroke populations. During the acute phase, 12 (36%) patients used ergotamines or triptans. Stroke was located in the posterior circulation in 27 (82%) patients and cerebellum was involved in 7 (21%). Except in two patients with brainstem infarctions, the outcome was favorable with total recovery or limited residual symptoms. CONCLUSIONS: The prevalence of traditional risk factors was low and the infarctions were predominantly located in posterior circulation territory, supporting theories of migraine specific mechanisms. The outcome was in general favorable.

Increased headache prevalence in female adolescents and adult women with early menarche. The Head-HUNT Studies.

BACKGROUND: Age at menarche is associated with cardiovascular events and lifestyle factors such as body mass index (BMI), certain women's diseases like breast cancer and endometriosis and with occurrence of certain physical symptoms during puberty. It is unclear whether age at menarche is an independent determinant of headache. OBJECTIVES: The aim of the study was to explore age of menarche in relation to headache prevalence in a large population-based study of both adolescents and adult women (HUNT). METHODS: In the Nord-Trøndelag Health Study in Norway 1995-97 (HUNT 2), a total of 26,636 (57%) of 46,506 invited women responded to questions regarding menarche and headache (Head-HUNT). In the youth part of HUNT 2, 3196 female students were interviewed about their headache complaints and 2766 (87%) responded to questions regarding menarche. All the final analyses were adjusted for age, use of oral contraceptives and BMI, and for adults also for educational level. RESULTS: Headache was more prevalent amongst females with menarche ≤ 12 years, both amongst adolescents (OR=1.3, 95% CI=1.1-1.5) and adults (OR=1.1, 95% CI=1.1-1.2), evident for migraine and non-migrainous headache. CONCLUSION: Headache, both migraine and non-migrainous headache, was more prevalent amongst both adolescents and adult females with early menarche. Early menarche may increase headache susceptibility, or be a consequence of a common pathogenetic factor, e.g., sensitivity to estrogens.

Headache, migraine and cardiovascular risk factors: the HUNT study.

BACKGROUND: Migraine with aura (MA) has been found to be a risk factor for cardiovascular disease including ischaemic stroke and myocardial infarction. Studies have also reported a higher prevalence of unfavourable cardiovascular risk factors amongst migraineurs, but results have been conflicting as to whether this is restricted to MA or also holds true for migraine without aura (MO). This study aims to examine the relation between headache and cardiovascular risk factors in a large cross-sectional population-based study. METHODS: A total of 48,713 subjects (age ≥ 20 years) completed a headache questionnaire and were classified according to the headache status in the Nord-Trøndelag Health Study in Norway 1995-1997 (HUNT 2). Framingham 10-year risk for myocardial infarction and coronary death could be calculated for 44,098 (90.5%) of these. Parameters measured were blood pressure, body mass index, serum total and high-density lipoprotein cholesterol. RESULTS: Compared to controls, Framingham risk score was elevated in non-migraine headache sufferers (OR 1.17, 95% CI 1.10-1.26), migraineurs without aura (OR 1.17, 95% CI 1.04-1.32) and most pronounced amongst migraineurs with aura (OR 1.54, 95% CI 1.21-1.95). Framingham risk score consistently increased with headache frequency. For non-migrainous headache and MO, the increased risk was accounted for by the lifestyle factors smoking, high BMI and low physical activity, whilst such factors did not explain the elevated risk associated with MA. CONCLUSIONS: Both MA, MO and non-migrainous headache are associated with an unfavourable cardiovascular risk profile, but different mechanisms seem to underlie the elevated risk in MA than in the other headache types.

Management of medication overuse headache: 1-year randomized multicentre open-label trial.

It is a general belief that patients with medication overuse headache (MOH) need withdrawal of acute headache medication before they respond to prophylactic medication. In this 1-year open-labelled, multicentre study intention-to-treat analyses were performed on 56 patients with MOH. These were randomly assigned to receive prophylactic treatment from the start without detoxification, undergo a standard out-patient detoxification programme without prophylactic treatment from the start, or no specific treatment (5-month follow-up). The primary outcome measure, change in headache days per month, did not differ significantly between groups. However, the prophylaxis group had the greatest decrease in headache days compared with baseline, and also a significantly more pronounced reduction in total headache index (headache days/month x headache intensity x headache hours) at months 3 (P = 0.003) and 12 (P = 0.017) compared with the withdrawal group. At month 12, 53% of patients in the prophylaxis group had > or = 50% reduction in monthly headache days compared with 25% in the withdrawal group (P = 0.081). Early introduction of preventive treatment without a previous detoxification programme reduced total headache suffering more effectively compared with abrupt withdrawal. (ClinicalTrials.gov number, NCT00159588).

Complications, reoperations, readmissions, and length of hospital stay in 34 639 surgical cases of lumbar disc herniation.

AIMS: The aims of this study were to determine the rates of surgical complications, reoperations, and readmissions following herniated lumbar disc surgery, and to investigate the impact of sociodemographic factors and comorbidity on the rate of such unfavourable events. PATIENTS AND METHODS: This was a longitudinal observation study. Data from herniated lumbar disc operations were retrieved from a large medical database using a combination of procedure and diagnosis codes from all public hospitals in Norway from 1999 to 2013. The impact of age, gender, geographical affiliation, education, civil status, income, and comorbidity on unfavourable events were analyzed by logistic regression. RESULTS: Of 34 639 operations, 2.7% (95% confidence interval (CI) 2.6 to 2.9) had a surgical complication, 2.1% (95% CI 2.0 to 2.3) had repeat surgery within 90 days, 2.4% (95% CI 2.2 to 2.5) had a non-surgical readmission within 90 days, and 6.7% (95% CI 6.4 to 6.9) experienced at least one of these unfavourable events. Unfavourable events were found to be associated with advanced age and comorbidity. CONCLUSION: The results suggest that surgical complications are less frequent than previously suggested. There are limited associations between sociodemographic patient characteristics and unfavourable events. Cite this article: Bone Joint J 2019;101-B:470-477.

Physical activity and headache: results from the Nord-Trøndelag Health Study (HUNT).

The aim of this study was to evaluate, using a prospective and a cross-sectional design, the relationship between level of physical activity and migraine and non-migraine headache. In the prospective part, 22,397 participants, not likely to have headache, answered questions about physical activity at baseline (1984-1986) and responded to a headache questionnaire at follow-up. In the cross-sectional part (1995-1997), 46,648 participants answered questions about headache and physical activity. Physically inactive individuals at baseline were more likely than active individuals to have non-migraine headache 11 years later (odds ratio 1.14, 95% confidence interval 1.02, 1.28). In the cross-sectional analyses, low physical activity was associated with higher prevalence of migraine and non-migraine headache. In both headache groups, there was a strong linear trend (P < 0.001) of higher prevalence of 'low physical activity' with increasing headache frequency. The result may indicate that physical inactivity among headache-free individuals is a risk factor for non-migraine headache and that individuals with headache are less physically active than those without headache.