Karin Magnusson

Norwegian Institute of Public Health & Lund University · NIPH: Health Services Research & LU: Clinical Epidemiology Unit

Objective: Familial confounding is confounding due to genetics or environmental exposures shared by family members. We aimed to study whether familial confounding explains the association between body mass index (BMI) and severe hip osteoarthritis (OA). Design: We linked data from the Norwegian Arthroplasty Registry with the Norwegian Twin Regis...

Objective To explore factors related to hand pain in persons with radiographic hand osteoarthritis (OA).Methods Persons in the Musculoskeletal Pain in Ullensaker Study with radiographic hand OA (≥1 joint with Kellgren/Lawrence grade ≥2) were included (n = 530). We examined the cross-sectional association between possible explanatory variables and h...

Objective: To explore and quantify the relative strengths of the genetic contribution vs. the contribution of modifiable environmental factors to severe osteoarthritis having progressed to total joint arthroplasty. Design: Incident data from the Norwegian Arthroplasty Registry were linked with the Norwegian Twin Registry on the National ID-numbe...

Objectives: Improved prediction modeling in osteoarthritis (OA) may encourage risk reduction through calculation of individual and population lifetime risks. There are currently no prediction models for hand OA. Thus, we aimed to i) develop a prediction model for hand OA in men and ii) to contrast its discriminative performance to a prediction mod...

Objective: To compare the prevalence of synovitis, pain and radiographic progression in non-erosive and erosive hand osteoarthritis (HOA), and to explore whether the different rate of disease progression is explained by different levels of synovitis and structural damage. Design: We included 31 and 34 participants with non-erosive and erosive HO...

Whereas the nature of the post-COVID condition following mild acute COVID-19 is increasingly well described in the literature, knowledge of its risk factors, and whether it can be predicted, remains limited. This study, conducted in Norway, uses individual-level register data from 214,667 SARS-CoV-2 infected individuals covering a range of demograp...

Aim: To explore whether children in specialist care with COVID-19 have increased post-discharge health care use when compared with children in specialist care with 1) respiratory syncytial virus (RSV) infection, and 2) other respiratory tract infections (RTIs). Methods: In 34,214 children aged 1 month to 5 years who were registered as having one...

Aim: To compare the genetic contribution to osteoarthritis (OA) vs other rheumatic/musculoskeletal diseases (RMDs) in the same population, and 2) to explore the role for any shared genetics between OA and other RMDs. Methods: In 59 970 Swedish twins aged 35 years or older, we estimated the heritability (the variance explained by genetic factors)...

Background Hand osteoarthritis (OA) pain is characterized as heterogeneous and multifactorial. Different pain patterns may be explained by underlying phenotypes, which previously have not been explored. Objectives Using the biopsychosocial framework, we aimed to identify possible hand OA phenotypes and explore the associations with pain intensity...

Objective: To determine whether the comorbidity burden and co-existing comorbidities are cross-sectionally and/or longitudinally associated with pain and pain sensitization in a cohort study of people with hand OA. Design: We examined whether comorbidity burden and individual comorbidities based on the self-administered Comorbidity Index (range:...

Background SARS-CoV-2 mRNA vaccination has been associated with both side effects and a reduction in COVID-related complaints due to the decrease in COVID-19 incidence. We aimed to investigate if individuals who received three doses of SARS-CoV-2 mRNA vaccines had a lower incidence of (a) medical complaints and (b) COVID-19-related medical complain...

Objectives To assess the impact of the COVID-19 pandemic on sick leave among healthcare workers (HCWs) in primary and specialist care and examine its causes. Methods Using individual-level register data, we studied monthly proportions of sick leave (all-cause and not related to SARS-CoV-2 infection) from 2017 to February 2022 for all HCWs in prima...

We studied the prevalence and patterns of typical long COVID complaints in ~ 2.3 million individuals aged 18–70 years with and without confirmed COVID-19 in a Nation-wide population-based prospective cohort study in Norway. Our main outcome measures were the period prevalence of single-occurring or different combinations of complaints based on medi...

Objective: General practitioners (GP) are often the first medical professionals to treat musculoskeletal complaints. Yet the impact of COVID-19 on primary care utilisation for musculoskeletal complaints is largely unknown. This study quantifies the impact of the pandemic on primary care utilisation for musculoskeletal complaints and specifically o...

Background Previous studies have reported an inverse association between educational attainment and different osteoarthritis (OA) outcomes. However, none of the previous studies have accounted for potential confounding by early-life environment and genetics. Thus, we aimed to examine the association between educational attainment and knee and hip O...

Aim To explore whether physiotherapy use is increased after hospitalization with COVID-19 with or without respiratory support vs. other respiratory tract infections (RTI). Methods In all Norwegian residents aged 18–80 years who were hospitalized with COVID-19 (N = 5,344) or other RTI (N = 82,235) between July 1st 2017 and August 1st 2021, we used...

The SARS-CoV-2 Omicron (B.1.1.529) variant has been associated with less severe acute disease, however, concerns remain as to whether long-term complaints persist to a similar extent as for earlier variants. Studying 1 323 145 persons aged 18-70 years living in Norway with and without SARS-CoV-2 infection in a prospective cohort study, we found tha...

Objective To investigate the value of ultrasonographic data in predicting total knee replacement (TKR). Design Data from the Musculoskeletal Pain in Ullensaker study (MUST) was linked to the Norwegian Arthroplasty Register to form a 5–7 year prospective cohort study of 630 persons (69% women, mean (SD) age 64 (8.7) years). We examined the predicti...

Background SARS-CoV-2 infection in children is followed by an immediate increase in primary care utilisation. The difference in utilisation following infection with the delta and omicron virus variants is unknown. Objectives To study whether general practitioner (GP) contacts were different in children infected with the omicron versus delta varian...

Background: A wide range of response strategies have been implemented by different countries to slow the spread of the COVID-19 outbreak. While the effects of these strategies in the general population have been investigated, less is known about the effects of these strategies on those with pre-existing comorbid conditions including rheumatic and m...

Objectives: To study the prevalence and patterns of typical post-covid complaints in ~2.3 million persons with and without confirmed COVID-19. Methods: In a Nation-wide population-based prospective cohort study, we studied all persons aged 18-70 years living in Norway and who tested positive (n=75 979), negative (n=1 167 582) and who were not teste...

Aims To examine whether individuals vaccinated with three doses of mRNA SARS-CoV-2 vaccines have an altered incidence of medical complaints compared to individuals not vaccinated with three doses. Methods Using longitudinal exact 1:1 matching on days since 2nd dose, calendar month and a set of covariates, we obtained a matched sample with 138 581...

Aims: To examine whether individuals vaccinated with three doses of mRNA SARS-CoV-2 vaccines have an altered incidence of medical complaints compared to individuals not vaccinated with three doses. Methods: Using longitudinal exact 1:1 matching on days since 2nd dose, calendar month and a set of covariates, we obtained a matched sample with 138 581...

Objective To estimate the genetic contribution to doctor-diagnosed hand osteoarthritis (OA). Methods Using data from the Swedish Twin Registry and National Patient Register, we conducted a 20-year population-based longitudinal cohort study including 59 970 twins aged 35 years or older. We studied inpatient and outpatient doctor-diagnosed hand OA u...

Background Hand osteoarthritis (OA) pain is heterogeneous and multifactorial, involving biological, psychological and social aspects extending beyond the OA disease process. Different phenotypes may differ in prognosis and treatments requirements, and thus be of clinical importance. The presence of hand OA phenotypes has not previously been examine...

Objective To examine whether persons infected with the SARS-CoV-2 omicron variant have an altered risk of post-covid complaints and healthcare use when compared to 1) persons testing negative, and 2) persons with delta. Design Prospective cohort study with 126 days follow-up and a time-to-event approach. Setting A registry-based study including N...

Objective To examine whether psychological symptoms and cognitive patterns are associated with self-reported pain and pain sensitization in people with hand osteoarthritis (OA). Design In the Nor-Hand study (n = 300), people with hand OA self-reported psychological symptoms (Hospital Anxiety and Depression Scale), cognitive patterns (Pain catastro...

Aim To explore whether the acute 30-day burden of COVID-19 on health care use has changed from February 2020 to February 2022. Methods In all Norwegians (N = 493 520) who tested positive for SARS-CoV-2 in four pandemic waves (February 26 th , 2020 –February 16 th , 2021 (1 st wave dominated by the Wuhan strain), February 17 th –July 10 th , 2021 (...

Objective To investigate whether the first wave of the COVID-19 pandemic impacted healthcare consultations (HCC) and hospitalization among people with and without osteoarthritis (OA). Methods Using register data, we included individuals aged ≥35 years residing in Skåne region, Sweden, during 2009–2019 with (n = 123,523) and without (n = 552,412) a...

Objectives: To explore whether and for how long use of healthcare services is increased among children and adolescents after covid-19. Design: Before and after register based study. Setting: General population of Norway. Participants: Norwegians aged 1-19 years (n=706 885) who were tested for SARS-CoV-2 from 1 August 2020 to 1 February 2021 (n=1...

Aim: To compare hospital admissions across common respiratory tract infections (RTI) in 2017-21, and project possible hospital admissions for the RTIs among children aged 0–12 months and 1-5 years in 2022 and 2023. Methods: In 644 885 children aged 0–12 months and 1–5 years, we plotted the observed monthly number of RTI admissions [upper- and lowe...

Objective To examine associations of pain sensitisation with tender and painful joint counts and presence of widespread pain in people with hand osteoarthritis (OA). Methods Pressure pain thresholds (PPT) at a painful finger joint and the tibialis anterior muscle, and temporal summation (TS) were measured in 291 persons with hand OA. We examined w...

Purpose To investigate the impact of COVID-19 in Sweden on rates of knee and hip surgeries. Methods We used healthcare data for the population of the southernmost region in Sweden (1.4 million inhabitants). We did an interrupted time-series analysis to estimate changes in rates and trends of joint replacements (JR), arthroscopies, and fracture sur...

Background: We aimed to explore whether children in hospital care with COVID-19 have increased post-discharge health care use when compared to children in hospital care with 1) RSV infection, and 2) other RTIs. Methods: In 34,214 children aged 1 month to 5 years who were registered with one or more hospital contacts with COVID-19 (N=128), RSV infec...

Background: To compare hospital admissions across common respiratory tract infections (RTI) in 2017-21, and project possible hospital admissions for the RTIs among children aged 0-12 months and 1-5 years in 2022 and 2023. Methods: In 644 885 children aged 0-12 months and 1-5 years, we plotted the observed monthly number of RTI admissions (upper- an...

Background Survey studies have found that vaccinated persons tend to report more side effects after being given information about side effects rather than benefits. However, the impact of high media attention about vaccine-related side effects on the utilization of health care is unknown. We aimed to assess whether utilization of health care servic...

Aim: To explore the temporal impact of mild COVID-19 on need for primary and specialist health care services. Methods: In all adults (≥20 years) tested for SARS-CoV-2 in Norway March 1st 2020 to February 1st 2021 (N = 1 401 922), we contrasted the monthly all-cause health care use before and up to 6 months after the test (% relative difference),...

Background The occupational risk of COVID-19 may be different in the first versus second epidemic wave. Aim To study whether employees in occupations that typically entail close contact with others were at higher risk of SARS-CoV-2 infection and COVID-19-related hospitalisation during the first and second epidemic wave before and after 18 July 202...

Background: Occupational exposure has been suggested to contribute to a disproportionate burden of COVID-19 among immigrants. We aim to assess this hypothesis in Norway. Methods: In 2729 627 adults born in Norway, Somalia, Pakistan, Iraq, Afghanistan and Turkey, we examined whether persons employed as taxi drivers, bus and tram drivers, child ca...

Objective Pain sensitization is associated with pain severity in persons with hand osteoarthritis (OA). What contributes to pain sensitization is unclear. This study explores whether hand OA pathologies and symptom duration are related to central sensitization. Method Participants with hand OA in the Nor-Hand study underwent bilateral hand radiogr...

Objective To assess how different bans on serving alcohol in Norwegian bars and restaurants were related to the detection of SARS-CoV-2 in bartenders and waiters and in persons in any occupation. Methods In 25 392 bartenders and waiters and 1 496 328 persons with other occupations (mean (SD) age 42.0 (12.9) years and 51.8% men), we examined the we...

Objective To assess whether utilization of health care services for newly vaccinated health care workers changed after media attention about fatal side effects of the AstraZeneca vaccine on March 11 th , 2021, and whether changes differed by age, sex, or occupation. Data sources We utilized individual-level data on health care use, vaccination, em...

Aim: To explore whether the acute 30-day burden of COVID-19 on health care use has changed from the beginning to the end of the pandemic. Methods: In all Norwegians (N=122 699) who tested positive for SARS-CoV-2 in three pandemic waves (March 1st-July 31st 2020 (1st wave), August 1st-December 31st 2020 (2nd wave), and January 1st-May 31st 2021 (3rd...

Objectives: To explore whether, and for how long COVID-19 among children gives an increase in use of health care services, when compared to children with no COVID-19. Methods: Studying all Norwegian residents aged 1-5, 6-15 and 16-19 years from August 1st 2020 to February 1st 2021 (N= 768 560), we contrasted rates of monthly all-cause primary and s...

Background Pain is a hallmark symptom of hand osteoarthritis (OA). A subset of people with hand OA display centrally driven pain characteristics. Pain is driven by person-related factors, but how comorbidities are related to the hand OA pain experience is undetermined. Changes in pain pathophysiology and pain levels by for instants low-grade inflam...

Background Many countries imposed lockdowns in March 2020, in anticipation of the “first wave” of COVID-19 and the massive healthcare resources required to meet its acute medical needs. Sweden adopted a different strategy to contain the epidemic, opting for non-binding recommendations. Nonetheless, elective and acute surgical procedures in health c...

Aim: To explore sick leave after COVID-19, by comparing doctor-certified sick leave for up to 6 months after testing for SARS-CoV-2 across employees who tested positive and negative. Methods: In all persons (20-70 year of age) with an employment contract, who were tested for the SARS-CoV-2 in Norway from March 1st to November 1st 2020 (N=740 182 wi...

Background and purpose — Many countries implemented strict lockdown policies to control the COVID-19 pandemic during March 2020. The impacts of lockdown policies on joint surgeries are unknown. Therefore, we assessed the effects of COVID-19 pandemic lockdown restrictions on the number of emergency and elective hip joint surgeries, and explored whet...

Aim To assess the role of occupation in the spread of COVID-19 among immigrants in Norway. Methods In 2.729.627 residents in Norway aged 20-70 years and born in Norway, Somalia, Pakistan, Iraq, Afghanistan and Turkey (mean [SD] age 44 (14) years and 51% men), we examined whether persons employed as taxi drivers, bus- and tram drivers, child care wo...

Objective To estimate the genetic contribution to traumatic and degenerative meniscus tears for men and women across the lifespan. Methods We linked the Swedish Twin Register with individual-level national healthcare data to form a 30-year, population-wide, longitudinal twin cohort. To study genetic contribution to meniscus tears, we estimated the...

Aim: To explore impacts of mild and severe COVID-19 on acute and long-term utilization of primary care, inpatient- and outpatient specialist health care. Methods: In all persons tested for the SARS-CoV-2 in Norway March 1st to November 1st 2020 (N=1 257 831), we used a difference-in-differences design to contrast the monthly health care use before...

Aim To study how different bans on serving alcohol in Norwegian bars and restaurants were related to the detection of SARS-CoV-2 in bartenders and waiters. Methods In 24,276 bartenders and waiters and 1,287,970 persons with other occupations (mean [SD] age 41.7 [12.8] years and 51.7% men), we examined the weekly rates of workers tested and detected...

Objectives: We aimed to determine the lifetime genetic risk for anterior cruciate ligament (ACL) rupture. Methods: We used a twin study approach, linking the Swedish Twin Register with national healthcare data to form a 30 year, population wide, longitudinal twin cohort. We studied ACL rupture in this cohort of 88 414 identical and fraternal twin p...

Aim To study whether employees in occupations that typically imply close contact with other people are at higher risk of SARS-CoV-2 infection (COVID-19) and related hospitalization, for the 1 st and 2 nd wave of infection in Norway. Methods In 3 553 407 residents of Norway on January 1 st 2020 aged 20-70 (with mean [SD] age 44.1 [14.3] years and 5...

Objective: To assess the effects of Covid-19 pandemic lockdown restrictions on the number of emergency and elective hip joint surgeries, and explore whether these procedures are more/less affected by lockdown restrictions than other hospital care. Methods: In 1.344.355 persons aged ≥35 years in the Norwegian emergency preparedness (BEREDT C19) regi...

Objective To explore whether magnetic resonance imaging (MRI) features suggestive of knee osteoarthritis (OA) are associated with presence of knee pain in possible early‐stage OA development. Methods We included 294 participants from the Osteoarthritis Initiative (mean ± SD age 50 ± 3 years; 50% women) with baseline Kellgren/Lawrence grade of 0 in...

Objectives: (1) To assess prognostic factors for patient-reported outcome measures (PROMs) and physical activity two to ten years after anterior cruciate ligament reconstruction (ACLR) or injury, and (2) to assess differences in prognostic factors between patients treated with ACLR and with rehabilitation alone. Design: Prognosis systematic revi...

Background Overweight and obesity are well-known risk factors for osteoarthritis (OA) in weight-bearing joints. However, the role of increased body mass index (BMI) and waist circumference in OA of the non-weight-bearing joints is more controversial. Few hand OA studies have explored the associations between increased BMI/waist circumference and pa...

Background Pressure pain threshold (PPT) is a measure of pain sensitization; altered pain mechanisms in the peripheral and/or central nervous system causing increased pain sensitivity. PPT testing may be a useful tool to classify pain phenotypes but requires special equipment not available in the clinic. The Doyle index (DI) is a clinical measure o...

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...

Objective Pain sensitization contributes to the complex osteoarthritis (OA) pain experience. The relationship between imaging features of hand OA and clinically assessed pain sensitization is largely unexplored. This study was undertaken to examine the association of structural and inflammatory features of hand OA with local pressure pain threshold...

Objectives: To estimate the risk of clinically diagnosed knee osteoarthritis (OA) after different types of knee injuries in young adults. Methods: In a longitudinal cohort study based on population-based healthcare data from Skåne, Sweden, we included all persons aged 25-34 years in 1998-2007 (n=149 288) with and without diagnoses of knee injuri...

Background Conditioned pain modulation (CPM) assesses adequacy of descending modulatory pathways. Temporal summation (TS) reflects ascending facilitation of nociceptive signals in the central nervous system (central sensitization). Inadequate CPM and enhanced TS of pain are both known to contribute to pain in chronic pain conditions. Different pain...

Background Increased sensitivity to pain in the area around joints with osteoarthritis (OA), i.e., peripheral sensitization, is associated with higher pain severity. The mechanisms underlying peripheral sensitization in hand OA have not been substantially explored in previous studies. Objectives We aimed to explore whether the severity of structur...

Background Despite no current knowledge of lesions or disease of the sensory nervous system in osteoarthritis (OA), subgroups of knee OA patients report neuropathic-like pain. The neuropathic-like pain component has been suggested to reflect central sensitization. Objectives To describe the prevalence of neuropathic-like pain in persons with hand...

Background Pain in osteoarthritis (OA) causes significant physical, psychological and social limitations. Increased understanding of the pain experience is important for improved patient care. Objectives We aimed to assess the pain characteristics of hand OA using the McGill Pain Questionnaire, a multidimensional self-reporting questionnaire that...

Objective It is currently unknown whether osteoarthritis (OA) is inherited mainly from the mother, father, or both. This study was undertaken to explore the effect of maternal and paternal factors on hip, knee, and hand OA in offspring. Methods Participants from the Musculoskeletal Pain in Ullensaker Study (MUST) (69% female; mean ± SD age 64 ± 9...

Objective: (1) To estimate the life-time genetic contribution for knee osteoarthritis (OA) surgery and (2) to explore any differences in the genetic contribution across age, sex and body mass index (BMI). Methods: We studied the sex-specific genetic contribution to knee OA surgery in a prospective cohort study of 62,490 twins aged 35 years or ol...

Objective Pain sensitization, an important osteoarthritis (OA) pain mechanism, has not been substantially investigated in patients with hand OA. It is unknown how peripheral and central sensitization are related to self‐reported hand pain. Methods Individuals with verified hand OA in the Nor‐Hand study underwent quantitative sensory testing of pre...

Aim: To study the development of early knee osteoarthritis (OA) in subjects with and without risk factors for knee OA. Methods: We studied 340 subjects from the Osteoarthritis Initiative, aged 45-55 years (51% women), free of radiographic knee OA at baseline (n=294 with and n=46 without knee pain and other OA risk factors). At baseline, 24, 48,...

Objective To compare the 6‐minute walking distance (6MWD) in a population‐based cohort of patients with osteoarthritis (OA) with that in matched peers from the general population, and to explore the associations between walking ability and risk of cardiovascular disease (CVD) in the OA cohort. Methods This cross‐sectional study included individual...

Objective To simplify the previously published Nottingham 12‐year risk prediction model for knee osteoarthritis (OA) and examine whether it can be used to predict the 40‐year risk of knee OA in young men. Methods Our cohort included 40,118 men who were 18 years of age and had undergone military conscription in Sweden from 1969 to 1970. Diagnostic...

Background Sensitisation, a hyperexcitability of nociceptive pathways, contributes to pain severity in patients with knee osteoarthritis, but this association has not yet been examined in patients with hand osteoarthritis (HOA). Objectives This study explored the occurrence of central and peripheral sensitisation in patients with HOA and the relat...

Background Pain is the most preferred area of improvement for patients with hand osteoarthritis (OA). Whereas only weak associations have been found between radiographic OA severity and pain, few studies have explored whether psychological factors are associated with pain. Objectives To examine whether radiographic severity, depression, anxiety an...

Background Patients with painful hand osteoarthritis (HOA) have enhanced central pain sensitisation (CS). Structural and inflammatory joint tissue damage over time might lead to CS. However, increased pain sensitisation can also represent an ‘a priori trait’ of a subgroup of patients. Objectives This study explored whether structural pathology, in...