Predicting work disability and the outcome of vocational rehabilitation : the role of persistent physical symptoms and mental health

Abstract In this Thesis, the relationship between Persistent Physical Symptoms (PPS), mental health, work disability and vocational rehabilitation outcome was examined in two samples. First, we looked at a sample of 324 people seeking vocational rehabilitation services and then at a subsample of 285 Non-Cardiac Chest Pain (NCCP) patients taken from a larger study on 504 chest pain patients that attended an Icelandic cardiac emergency department (CED). The participants in the vocational rehabilitation sample were between 18 and 65 years old, their mean age was 39.34 years and the majority of them were female (78.1%). Participants in NCCP study were between 18 and 66 years old, their mean age was 49.84 years and about half of them were female (54.0%) and a half of them male (46.0%). In both samples, participants filled out questionnaires measuring PPS and mental health problems. Information regarding the rehabilitation of the vocational rehabilitation service seekers and medical diagnoses of the chest pain patients was retrieved from the service providers. In the vocational rehabilitation sample, we firstly estimated the prevalence of PPS, examined how the extent of PPS related to mental health problems, and estimated how many rehabilitation seekers might benefit from psychological treatment for PPS. Secondly, we investigated whether the outcome of vocational rehabilitation and functional impairment at its beginning could be predicted by the presence of PPS, specific PPS types or symptoms of psychological distress using logistic- and hierarchical linear regression. In the CED sample, we examined the relationship between PPS, mental health and work disability from another angle by looking at patients diagnosed with NCCP. NCCP patients whose symptoms were severe enough to meet PPS criteria (n=85) were compared to other NCCP (n=200) patients in terms of work status, psychological symptoms, and total number of PPS. In our vocational rehabilitation sample, the prevalence of PPS was 80.9%, and the modal number of symptoms was three. Participants with PPS more commonly had depression, anxiety and health anxiety symptoms in the clinical range, and these symptoms were positively correlated with the number of PPS. Between 46.2% and 64.6% of our participants were identified as being likely to benefit from a specialised PPS treatment. Functional impairment at the beginning of service was predicted by depressive symptoms, PPS and social anxiety symptoms. Only persistent pain and depressive symptoms independently predicted not returning to work, and the rehabilitation duration was not related to the severity or number of psychological symptoms nor the presence or number of PPS. In the CED sample, NCCP patients whose symptoms met PPS criteria reported more symptoms of depression, anxiety and health anxiety than other NCCP patients. They also ruminated more, had a higher number of other PPS and were more likely to be inactive or unable to work. Within Icelandic vocational rehabilitation, special attention should be given to PPS and depressive symptoms as they are common, positively associated with functional impairment at the beginning of service and a specific combination of these symptoms was associated with a lower return to work rate. Overall, the results suggest a clear need for routine evaluation and specialised treatment for PPS within vocational rehabilitation and that such treatments should preferably be both transdiagnostic and work focussed. Furthermore, the results indicate that there might be value in identifying and treating PPS at earlier stages, such as through the CED.VIRK - Vocational Rehabilitation Fund RU Research Fun

Seismic imaging in the Krafla high-temperature geothermal field, NE Iceland, using zero- and far-offset vertical seismic profiling (VSP) data

The research leading to these results has received funding from the European Community's Seventh Framework Program under grant agreement No. 608553 (Project IMAGE). We thank Landsvirkjun, the operator of the Krafla geothermal field, for technical and logistical support during the survey. We also thank the Operational Support Group of the International Continental Scientific Drilling Program (ICDP) for their technical support. We further acknowledge the support from the Research Council of Norway through its Centres of Excellence funding scheme, project 22372 (SP).Peer reviewedPostprin

Tomographic image of the Mid-Atlantic Plate Boundary in southwestern Iceland

Publisher's version (útgefin grein)The 170 km South Iceland Seismic Tomography (SIST) profile extends from the west and across the Mid‐Atlantic Ridge spreading center in the Western Volcanic Zone and continues obliquely through the transform zone (the South Iceland Seismic Zone) to the western edge of the Eastern Volcanic Zone. A total of 11 shot points and 210 receiver points were used, allowing precise travel times to be determined for 1050 crustal P wave rays and 180 wide‐angle reflections. The large amplitudes of the wide‐angle reflections and an apparent refractor velocity of 7.7 km/s are interpreted to be from a relatively sharp Moho at a depth of 20–24 km. This interpretation differs from the earlier models (based on data gathered in the 1960s and 1970s), of a 10–15 km thick crust underlain by a upper mantle with very slow velocity of 7.0–7.4 km/s. Nevertheless, these older data do not contradict our new interpretation. Implication of the new interpretation is that the lower crust and the crust‐mantle boundary are colder than previously assumed. A two‐dimensional tomographic inversion of the compressional travel times reveals the following structures in the crust: (1) a sharp increase in thickness of the upper crust (“layer 2A”) from northwest to southeast and (2) broad updoming of high velocity in the lower crust in the Western Volcanic Zone, (3) depth to the lower crust (“layer 3”) increases gradually from 3 km at the northwestern end of the profile to 7 km at the southeastern end of the profile, (4) a low‐velocity perturbation extends throughout the upper crust and midcrust into the lower crust in the area of the transform in south Iceland (South Iceland Seismic Zone), and (5) an upper crustal high‐velocity anomaly is associated with extinct central volcanos northwest of the Western Volcanic Zone. The travel time data do not support the existence of a large (> 0.5 km thick) crustal magma chamber in this part of the Western Volcanic Zone but do not exclude the possibility of a smaller one.This research was supported by the U.S. National Science Foundation, the Iceland National Science Foundation, the National Energy Authority of Iceland, the Incorporated Research Institutions for Seismology, IcelandAir, and the Lamont-Doherty Geological Observatory of Columbia University.Peer Reviewe

Non-Cardiac Chest Pain as a Persistent Physical Symptom : Psychological Distress and Workability

Funding Information: The authors thank the Graduate Program in Agricultural Engineering of the Federal University of Campina Grande, the National Council for Scientific and Technological Development (CNPq), and the Coordination for the Improvement of Higher Education Personnel (CAPES) for the financial support in carrying out this research. Funding Information: The larger study, which this study is part of, was supported by Icelandic Research Fund under Grant 152207-051 and the University Hospital Science Fund under Grant A-2019-023, A-2018-047 and A-2017-051. Publisher Copyright: © 2023 by the authors.Non-Cardiac Chest Pain (NCCP) is persistent chest pain in the absence of identifiable cardiac pathology. Some NCCP cases meet criteria for Persistent Physical Symptoms (PPS), where the symptoms are both persistent and distressing/disabling. This study aimed to identify patients that might need specialist treatment for PPS by examining cases of NCCP that meet PPS criteria. We analysed data from 285 chest pain patients that had received an NCCP diagnosis after attending an emergency cardiac department. We compared NCCP patients who did and did not meet the additional criteria for heart-related PPS and hypothesised that the groups would differ in terms of psychological variables and workability. We determined that NCCP patients who meet PPS criteria were more likely than other NCCP patients to be inactive or unable to work, reported more general anxiety and anxiety about their health, were more depressed, ruminated more, and, importantly, had a higher number of other PPS. A high proportion of NCCP patients meet PPS criteria, and they are similar to other PPS patients in terms of comorbidity and disability. This highlights the importance of focusing psychological interventions for this subgroup on the interplay between the range of physical and psychological symptoms present.Peer reviewe

Crustal Formation on a Spreading Ridge Above a Mantle Plume: Receiver Function Imaging of the Icelandic Crust

Iceland sits astride a mid-ocean ridge underlain by a {mantle} hotspot. The interplay of these two geological processes has the potential to generate a complex and laterally variable crustal structure. The thickness of the Icelandic crust is a long running and controversial debate, with estimates ranging from a "thin'' 20 km crust to a "thick'' 40 km crust. We present new images of the first order seismic discontinuity structure of the Icelandic crust based on a joint inversion of receiver function and ambient noise derived surface wave dispersion data. Inversion results are validated through comparison to receiver functions multi-phase common conversion point stacks across the densely instrumented Northern Volcanic Zone. We find a multi-layered crustal structure consisting of a 6-10 km deep upper crust underlain by either one or two discontinuities. The shallower discontinuity is found at depths of ~20 km throughout Iceland. The deeper discontinuity is only present in some regions, defining the base of a lens-like lower layer with maximum depths of 44 km above the center of the mantle plume. Either of these two discontinuities could be interpreted as the seismic Moho, providing an explanation why previous estimates of crustal thickness have diverged. Such structure may form via underplating of a pre-existing oceanic crust as has been hypothesized in other ocean island plume settings. However we demonstrate with a simple petrological model that variability in seismic discontinuity structure can also be understood as a consequence of compositional variation in melts generated with distance from the plume center

Sub-surface geology and velocity structure of the Krafla high temperature geothermal field, Iceland : Integrated ditch cuttings, wireline and zero offset vertical seismic profile analysis

The research leading to these results has received funding from the European Community's Seventh Framework Programme under grant agreement No. 608553 (Project IMAGE). The VMAPP project run by VBPR, DougalEARTH Ltd. and TGS also contributed funding to the borehole characterization of the K-18 borehole. Landsvirkun is acknowledged for their effort and assistance in this work and in particular for allowing the use of the data from well K-18. We further acknowledge the support from the Research Council of Norway through its Centres of Excellence funding scheme, project 22372 (SP and DAJ).Peer reviewedPostprin

Cyclical geothermal unrest as a precursor to Iceland’s 2021 Fagradalsfjall eruption

Understanding and constraining the source of geodetic deformation in volcanic areas is an important component of hazard assessment. Here, we analyse deformation and seismicity for one year before the March 2021 Fagradalsfjall eruption in Iceland. We generate a high-resolution catalogue of 39,500 earthquakes using optical cable recordings and develop a poroelastic model to describe three pre-eruptional uplift and subsidence cycles at the Svartsengi geothermal field, 8 km west of the eruption site. We find the observed deformation is best explained by cyclic intrusions into a permeable aquifer by a fluid injected at 4 km depth below the geothermal field, with a total volume of 0.11 ± 0.05 km3 and a density of 850 ± 350 kg m–3. We therefore suggest that ingression of magmatic CO2 can explain the geodetic, gravity and seismic data, although some contribution of magma cannot be excluded

The lithosphere and asthenosphere of the Iceland hotspot from surface waves

1-D models were calculated for the velocity of shear waves, polarized vertically (SV) and horizontally (SH) from dispersed Rayleigh and Love surface waves. These had been recorded in Iceland by the ICEMELT broad-band seismic network, with about half of the waves coming from near-distance earthquakes (≤1000 km). The analysis included unusually short periods, as brief as 5.0 s, and periods ranging up to 93 s. The Icelandic crust was revealed to have two basic layers: first, the upper and middle crust, which were largely detected as one layer, and second the layer of the lower crust. The half of Iceland surveyed had a weighted average crustal thickness of 25–26 km, less than previously estimated. It is under East and East Central Iceland that the crust is thickest, averaging 29–32 ± 3 km, and under the western margin of the West Fjords, 29 ± 2 km. The thinnest parts of the crust lie in West Central Iceland, 19 ± 1 km, and in the West Volcanic (or Rift) Zone, 19[+6/−1] km. This study examined how thicker crust away from the rift zone can be fitted with dynamic crust formation models. Possible explanations for different thicknesses include both crustal squeezing flow and imbalances between widths of the volcanic accretion and extensional stretching zones. The crust has highly anisotropic zones, with differences of up to 20 per cent between SV and SH velocities. Under rift zones, the lower crust is characterized by low velocities and, at depths of 8–18 km, by a channel with yet lower velocities. The lowest shear velocity in this channel is 5–9 per cent less than in the standard Icelandic velocity model. The thinnest lithosphere, 20 ± 2 km, lies under the East Central and North Volcanic Zones, where it extends up into the crust, while the thickest lithosphere is under East Iceland and the east shelf, nowhere less than 100 ± 20 km. This substantial contrast in lithosphere thickness of some 80 km occurs within a lateral distance of 100–150 km, implying an age unconformity at depth of several tens of millions of years. The thick East Iceland lithosphere may reduce or obstruct any eastward flow of the plume head. On the opposite side of the plume head, in Northwest Iceland and the West Fjords, the lithosphere is estimated to be 60 ± 10 km thick. Excepting the West Fjords and East Iceland, shear wave velocities are low in the island's subcrustal mantle, up to 7–9 per cent below the world average according to the PREM model. This indicates a warm, partially molten mantle under much of Central Iceland and the active rift zones. There is a lateral difference of 10–12 per cent in shear velocity between the shallowest mantle asthenosphere under Central Iceland and under the mantle lid to each side, that is, under the West Fjords and East Iceland. In the shallowest Central Iceland mantle, Vp/Vs-ratios suggest near solidus temperatures and a partial melt of 2–3 per cent. This paper describes structural variations in the asthenosphere down to 75–200 km. The low-velocity zone found 100–125 km below Central Iceland and the major part of western Iceland is interpreted as the onset of mantle plume melting. Mantle anisotropy is pronounced beneath Iceland, with SH and SV velocities differing by up to 10 per cent. The anisotropy structure is 3-D and normally reaches higher values in the asthenosphere than in the mantle lid. The main factor determining the asthenosphere's generally azimuthal anisotropy may be the lattice-preferred orientation (LPO) induced by flow. Based on this interpretation and the observed anisotropy, it follows that the plume head is flowing westwards at a depth of 60–110 km. The deeper, more pervasive North Atlantic flow is towards the northwest, leading to differential shearing. However, LPO anisotropy alone would perhaps remain under 8per cent, without the contributing factor of systematic melt distribution.Financial support by National Science Foundation (USA) (grants EAR-9316137, OCE-9402991) the Icelandic Research Center (RANNIS), the University of Iceland research fund and the German Academic Exchange Service (DAAD) is acknowledged.Peer Reviewe