Maximal respiratory pressure after COVID-19 compared with reference material in healthy adults: A prospective cohort study (The SECURe study).

After COVID-19 long term respiratory symptoms and reduced lung function including maximal inspiratory pressure (MIP) and maximal expiratory pressure (MEP) have been reported. However, no studies have looked at MIP and MEP in all disease groups and the reference materials collection methods differ substantially. We aimed to determine MIP and MEP in individuals after COVID-19 infection with different disease severity using reference material of healthy control group obtained using the same standardized method. Patients with COVID-19 were included March 2020-March 2021 at Rigshospitalet, Denmark. MIP and MEP were measured using microRPM. Predicted MIP and MEP were calculated using reference material obtained from 298 healthy adults aged 18-97 years using the same method. In SECURe, 145 participants were measured median 5 months after COVID-19 diagnosis and of these 16% had reduced MIP and/or MEP. There was reduced spirometry and total lung capacity, but not reduced diffusion capacity in those with abnormal MIP and/or MEP compared with normal MIP and MEP. Of those with reduced MIP and/or MEP at 5 months, 80% still had reduced MIP and/or MEP at 12 months follow-up. In conclusion, few have reduced MIP and/or MEP 5 months after COVID-19 and little improvement was seen over time.

The indication for total hip arthroplasty and its durability.

The most frequent indication for total hip arthroplasty (THA) is hip osteoarthritis. THA is inserted to improve function, reduce pain, and improve quality of life. Results are generally good, and 90-95% of the patients are satisfied. However, there are risks associated with THA, and patients must be well informed. Before THA is considered, non-surgical treatment must be completed, as the need for surgery often is postponed. Patients can expect rapid mobilisation and a return to a near-habitual level of physical activity within a year. In Denmark, 95% have their THA after five years and 76% after 25 years.

Implementation of health-promoting retail initiatives in the Healthier Choices in Supermarkets Study-qualitative perspectives from a feasibility study.

BACKGROUND: Improving food environments like supermarkets has the potential to affect customers' health positively. Scholars suggest researchers and retailers collaborate closely on implementing and testing such health-promoting interventions, but knowledge of the implementation of such interventions is limited. We explore the implementation of four health-promoting food retail initiatives selected and developed by a partnership between a research institution, a large retail group, and a non-governmental organisation. METHODS: The four initiatives included downsizing of bags for pick'n' mix sweets and soda bottles at the check-out registers, shelf tags promoting healthier breakfast cereal options, and replacing a complimentary bun with a banana offered to children. The initiatives were implemented for 6 weeks (or longer if the store manager allowed it) in one store in Copenhagen, Denmark. Data were collected through observations, informal interviews with customers, and semi-structured interviews with retailers. We conducted a thematic analysis of transcripts and field notes inspired by process evaluation concepts and included quantitative summaries of selected data. RESULTS: Two out of four initiatives were not implemented as intended. The implementation was delayed due to delivery issues, which also resulted in soda bottles not being downsized as intended. The maintenance of the shelf tags decreased over time. Retailers expressed different levels of acceptability towards the initiatives, with a preference for the complimentary banana for children. This was also the only initiative noticed by customers with both positive and negative responses. Barriers and facilitators of implementation fell into three themes: Health is not the number one priority, general capacity of retailers, and influence of customers and other stakeholders on store operation. CONCLUSIONS: The retailers' interests, priorities, and general capacity influenced the initiative implementation. Retailers' acceptability of the initiatives was mixed despite their involvement in the pre-intervention phase. Our study also suggests that customer responses towards health-promoting initiatives, as well as cooperation with suppliers and manufacturers in the development phase, may be determining to successful implementation. Future studies should explore strategies to facilitate implementation, which can be applied prior to and during the intervention.

Long term exposure to road traffic noise and air pollution and risk of infertility in men and women: nationwide Danish cohort study.

OBJECTIVE: To investigate associations between long term residential exposure to road traffic noise and particulate matter with a diameter <2.5 µm (PM2.5) and infertility in men and women. DESIGN: Nationwide prospective cohort study. SETTING: Denmark. PARTICIPANTS: 526 056 men and 377 850 women aged 30-45 years, with fewer than two children, cohabiting or married, and residing in Denmark between 2000 and 2017. MAIN OUTCOME MEASURE: Incident infertility in men and women during follow-up in the Danish National Patient Register. RESULTS: Infertility was diagnosed in 16 172 men and 22 672 women during a mean follow-up of 4.3 years and 4.2 years, respectively. Mean exposure to PM2.5 over five years was strongly associated with risk of infertility in men, with hazard ratios of 1.24 (95% confidence interval 1.18 to 1.30) among men aged 30-36.9 years and 1.24 (1.15 to 1.33) among men aged 37-45 years for each interquartile (2.9 µg/m3) higher PM2.5 after adjustment for sociodemographic variables and road traffic noise. PM2.5 was not associated with infertility in women. Road traffic noise (Lden, most exposed facade of residence) was associated with a higher risk of infertility among women aged 35-45 years, with a hazard ratio of 1.14 (1.10 to 1.18) for each interquartile (10.2 dB) higher five year mean exposure. Noise was not associated with infertility among younger women (30-34.9 years). In men, road traffic noise was associated with higher risk of infertility in the 37-45 age group (1.06, 1.02 to 1.11), but not among those aged 30-36.9 years (0.93, 0.91 to 0.96). CONCLUSIONS: PM2.5 was associated with a higher risk of an infertility diagnosis in men, whereas road traffic noise was associated with a higher risk of an infertility diagnosis in women older than 35 years, and potentially in men older than 37 years. If these results are confirmed in future studies, higher fertility could be added to the list of health benefits from regulating noise and air pollution.

Occupational and Health-Related Risk Factors for Incident and Recurrent Back Disorders in Danish Fishers-A Register-Based Study.

BACKGROUND: Fishers are at risk of back disorders due to their physically demanding work. The aim was to investigate risk factors for back disorders in fishers in Denmark. METHODS: All male Danish registered fishers between 1994 and 2017 were included. ICD-10 codes classified back disorders (M40-M54* and DM99.1-4*). A multistate model on a cause-specific cox regression model was conducted. RESULTS: Of 13,165 fishers included, 16% had a hospital contact with an incident back disorder, and 52% at least had 1 recurrent episode. Having worked in another occupation (HR 1.14; 95% CI: 1.02, 1.27) and another musculoskeletal disorder (HR 1.84; 95% CI: 1.69, 2.01) were significant risk factors for the incident back disorder. No risk factors were seen for recurrent episodes. CONCLUSIONS: Risk factors for incident and recurrent back disorders were different; thus, episode-specific initiatives are needed to reduce back disorders among fishers.

Cost-effectiveness analysis of app-delivered self-management support (selfBACK) in addition to usual care for people with low back pain in Denmark.

OBJECTIVES: This study aims to investigate the cost-effectiveness of individually tailored self-management support, delivered via the artificial intelligence-based selfBACK app, as an add-on to usual care for people with low back pain (LBP). DESIGN: Secondary health-economic analysis of the selfBACK randomised controlled trial (RCT) with a 9-month follow-up conducted from a Danish national healthcare perspective (primary scenario) and a societal perspective limited to long-term productivity in the form of long-term absenteeism (secondary scenario). SETTING: Primary care and an outpatient spine clinic in Denmark. PARTICIPANTS: A subset of Danish participants in the selfBACK RCT, including 297 adults with LBP randomised to the intervention (n=148) or the control group (n=149). INTERVENTIONS: App-delivered evidence-based, individually tailored self-management support as an add-on to usual care compared with usual care alone among people with LBP. OUTCOME MEASURES: Costs of healthcare usage and productivity loss, quality-adjusted life-years (QALYs) based on the EuroQol-5L Dimension Questionnaire, meaningful changes in LBP-related disability measured by the Roland-Morris Disability Questionnaire (RMDQ) and the Pain Self-Efficacy Questionnaire (PSEQ), costs (healthcare and productivity loss measured in Euro) and incremental cost-effectiveness ratios (ICERs). RESULTS: The incremental costs were higher for the selfBACK intervention (mean difference €230 (95% CI -136 to 595)), where ICERs showed an increase in costs of €7336 per QALY gained in the intervention group, and €1302 and €1634 for an additional person with minimal important change on the PSEQ and RMDQ score, respectively. At a cost-effectiveness threshold value of €23250, the selfBACK intervention has a 98% probability of being cost-effective. Analysis of productivity loss was very sensitive, which creates uncertainty about the results from a societal perspective limited to long-term productivity. CONCLUSIONS: From a healthcare perspective, the selfBACK intervention is likely to represent a cost-effective treatment for people with LBP. However, including productivity loss introduces uncertainty to the results. TRIAL REGISTRATION NUMBER: NCT03798288.

Identifying microbiome-based changes and biomarkers prior to disease development in mother and child, with a focus on gestational diabetes mellitus: protocol for the DANish Maternal and Offspring Microbiome (DANMOM) cohort study.

INTRODUCTION: The human gut microbiota is associated with gestational diabetes mellitus (GDM), which imposes a risk of developing long-term health problems for mother and child. Most studies on GDM and microbiota have been cross-sectional, which makes it difficult to make any conclusions on causality. Furthermore, it is important to assess if a dysbiotic microbiota is passed from the mother to the child, and then being at risk of developing metabolic health problems later in life. The DANish Maternal and Offspring Microbiome study aims to identify gut microbiota-related factors involved in metabolic dysfunction in women with GDM and their offspring. Importantly, the study design allows for early detection of biological changes associated with later development of metabolic disease. This could provide us with unique tools to support early diagnosis or implement preventative measures. METHODS AND ANALYSIS: Pregnant women are included in the study after the 11-14 weeks' prenatal ultrasound scan and followed throughout pregnancy with enrolment of the offspring at birth. 202 women and 112 children have been included from North Denmark Regional Hospital and Aalborg University Hospital in Denmark. Mother and child are followed until the children reach the age of 5 years. From the mother, we collect faeces, urine, blood, saliva, vaginal fluid and breast milk samples, in addition to faeces and a blood sample from the child. Microbiota composition in biological samples will be analysed using 16S rRNA gene sequencing and compared with demographic and clinical data from medical charts, registers and questionnaires. Sample and data collection will continue until July 2028. ETHICS AND DISSEMINATION: The study protocol has been approved by the North Denmark Region Committee on Health Research Ethics (N20190007). Written informed consent is obtained from all participants prior to study participation. Study results will be published in international peer-reviewed journals and presented at international conferences. The results will also be presented to the funders of the study and study participants.

Maternal age and body mass index and risk of labor dystocia after spontaneous labor onset among nulliparous women: A clinical prediction model.

INTRODUCTION: Obstetrics research has predominantly focused on the management and identification of factors associated with labor dystocia. Despite these efforts, clinicians currently lack the necessary tools to effectively predict a woman's risk of experiencing labor dystocia. Therefore, the objective of this study was to create a predictive model for labor dystocia. MATERIAL AND METHODS: The study population included nulliparous women with a single baby in the cephalic presentation in spontaneous labor at term. With a cohort-based registry design utilizing data from the Copenhagen Pregnancy Cohort and the Danish Medical Birth Registry, we included women who had given birth from 2014 to 2020 at Copenhagen University Hospital-Rigshospitalet, Denmark. Logistic regression analysis, augmented by a super learner algorithm, was employed to construct the prediction model with candidate predictors pre-selected based on clinical reasoning and existing evidence. These predictors included maternal age, pre-pregnancy body mass index, height, gestational age, physical activity, self-reported medical condition, WHO-5 score, and fertility treatment. Model performance was evaluated using the area under the receiver operating characteristics curve (AUC) for discriminative capacity and Brier score for model calibration. RESULTS: A total of 12,445 women involving 5,525 events of labor dystocia (44%) were included. All candidate predictors were retained in the final model, which demonstrated discriminative ability with an AUC of 62.3% (95% CI:60.7-64.0) and Brier score of 0.24. CONCLUSIONS: Our model represents an initial advancement in the prediction of labor dystocia utilizing readily available information obtainable upon admission in active labor. As a next step further model development and external testing across other populations is warranted. With time a well-performing model may be a step towards facilitating risk stratification and the development of a user-friendly online tool for clinicians.

Is something rotten in the state of Denmark? Cross-national evidence for widespread involvement but not systematic use of questionable research practices across all fields of research.

Questionable research practices (QRP) are believed to be widespread, but empirical assessments are generally restricted to a few types of practices. Furthermore, conceptual confusion is rife with use and prevalence of QRPs often being confused as the same quantity. We present the hitherto most comprehensive study examining QRPs across scholarly fields and knowledge production modes. We survey perception, use, prevalence and predictors of QRPs among 3,402 researchers in Denmark and 1,307 in the UK, USA, Croatia and Austria. Results reveal remarkably similar response patterns among Danish and international respondents (τ = 0.85). Self-reported use indicates whether respondents have used a QRP in recent publications. 9 out of 10 respondents admitted using at least one QRP. Median use is three out of nine QRP items. Self-reported prevalence reflects the frequency of use. On average, prevalence rates were roughly three times lower compared to self-reported use. Findings indicated that the perceived social acceptability of QRPs influenced self-report patterns. Results suggest that most researchers use different types of QRPs within a restricted time period. The prevalence estimates, however, do not suggest outright systematic use of specific QRPs. Perceived pressure was the strongest systemic predictor for prevalence. Conversely, more local attention to research cultures and academic age was negatively related to prevalence. Finally, the personality traits conscientiousness and, to a lesser degree, agreeableness were also inversely associated with self-reported prevalence. Findings suggest that explanations for engagement with QRPs are not only attributable to systemic factors, as hitherto suggested, but a complicated mixture of experience, systemic and individual factors, and motivated reasoning.

The intensive care population profile in Denmark before and during the first wave of the SARS-CoV-2 pandemic; a national register-based study.

OBJECTIVE: To describe the change in admission rate and demographic profile of patients admitted to ICUs throughout Denmark before and during first wave of the SARS-CoV-2 pandemic. METHODS: A register-based national observational study of all patients admitted to ICU from December 2019 until April 2020, comparing ICU admission before and after lockdown. RESULTS: The number of admissions declined, especially in the age groups below 18 and above 70. The sex distribution and the comorbidity-level remained unchanged. The length of hospital stay prior to ICU admission increased. Overall fewer patients were admitted electively. CONCLUSION: Fewer patients were admitted to ICU and waited longer for admission during the first wave of the COVID-19 pandemic.

Guest Editorial - Shifting Dynamics: ICU Admissions in Denmark during the First Wave of the COVID-19 Pandemic.

The advent of the SARS-CoV-2 pandemic brought unprecedented challenges to healthcare systems worldwide. As the virus spread across continents, hospitals faced a surge in patient admissions, particularly to intensive care units (ICUs). Understanding the impact of the pandemic on the sickest patients admitted to hospital is crucial for enhancing preparedness for future outbreaks. In this edition of the journal, authors from Denmark report on a register-based national observational study that sheds light on the changes in ICU admission rates and demographic profiles of patients during the initial phase of the pandemic.

Predicting Patient No-Shows: Situated Machine Learning with Imperfect Data.

Patients who do not show up for scheduled appointments are a considerable cost and concern in healthcare. In this study, we predict patient no-shows for outpatient surgery at the endoscopy ward of a hospital in Denmark. The predictions are made by training machine leaning (ML) models on available data, which have been recorded for purposes other than ML, and by doing situated work in the hospital setting to understand local data practices and fine-tune the models. The best performing model (XGBoost with oversampling) predicts no-shows at sensitivity = 0.97, specificity = 0.66, and accuracy = 0.95. Importantly, the situated work engaged local hospital staff in the design process and led to substantial quantitative improvements in the performance of the models. We consider the results promising but acknowledge that they are from a single ward. To transfer the no-show models to other wards and hospitals, the situated work must be redone.

Evaluating the Usability of a Telehealth System for People with COPD: A Cross Sectional Study.

Pulmonary Disease (COPD) exacerbations. However, the effect of telehealth for COPD remains uncertain, which may be due to a lack of attention to usability during the development of telehealth solutions. The aim was to evaluate the usability of a telehealth system for COPD using the Danish Telehealth Usability Questionnaire. A total of 96 people with COPD, who were already using a telehealth system consisting of weekly measurements of physiological parameters and symptom-related questionnaires, were included. The D-TUQ was used to assess the usability of the telehealth system. The overall experience with the usability of the telehealth system was mainly positive, but there was room for improvement.

New taxa of quill mites (Acariformes: Syringophilidae) parasitising aquatic birds of the Faroe Islands.

The paper presents descriptions of new taxa and new records of quill mites of the family Syringophilidae Lavoipierre, 1953 (Acari: Prostigmata: Cheyletoidea) parasitising aquatic birds in the Faroe Islands, Denmark. Sulisyringophilus jenskjeldi n. gen., n. sp., is described from the northern gannet, Morus bassanus (Linnaeus) (Suliformes: Sulidae). The new genus, Sulisyringophilus, is new genus differs from the morphologically similar genus Procellariisyringophilus Schmidt and Skoracki, 2007 by the presence of lateral hypostomal teeth and leg setae vsII in females, the features which are absent in the latter. A new species Charadriphilus lymnocryptes n. sp. is described from the jack snipe, Lymnocryptes minimus (Brünnich) (Charadriiformes: Scolopacidae). Additionally, two rarely recorded species, Niglarobia ereuneti Kethley, 1970, and Creagonycha lara Kethley, 1970, are reported from two charadriiform hosts: the semipalmated sandpiper, Calidris pusilla (Linnaeus) and the black-legged kittiwake, Rissa tridactyla (Linnaeus), respectively.

Prevalence of online sexual harassment and online bullying: a nationwide survey among high school students in Denmark.

Background: Using data from a nationwide survey among high school students in Denmark, the aim of the current study is to measure the prevalence of online bullying and online sexual harassment and assess gender and age differences in exposure. Methods: We used data from the Danish National Youth Study 2019, which is a nationwide web survey among high school students, including general, commercial, preparatory and technical high schools. Data were collected from January to April 2019 through a self-administered questionnaire in the classroom. A total of 29,086 students participated (response rate: 66%). The survey included questions about online sexual harassment (victimization and perpetration) and online bullying. Results: Approximately 11% of students reported receiving sexually offensive inquiries online, and about 10% received a sexual image/video of others without the subjects' consent. Additionally, 4% experienced that other people shared a sexual image/video of them without their consent within the last 12 months. The most common type of online bullying was feeling ignored by others online (25%), followed by someone spreading rumors or writing nasty things about them (13%), and receiving threats/unpleasant messages (12%). Gender results were mixed.

Risk of prolonged postoperative opioid use after elective shoulder replacement: a nationwide cohort study of 5,660 patients from the Danish Shoulder Arthroplasty Registry.

BACKGROUND AND PURPOSE: Several studies from the United States report an increased risk of prolonged opioid use after shoulder replacement. We aimed to determine the incidence and risk factors of prolonged opioid use after elective shoulder replacement in a nationwide Danish population. METHODS: All primary elective shoulder arthroplasties reported to the Danish Shoulder Arthroplasty Registry (DSR) from 2004 to 2020 were screened for eligibility. Data on potential risk factors was retrieved from the DSR and the National Danish Patient Registry while data on medication was retrieved from the Danish National Health Service Prescription Database. Prolonged opioid use was defined as 1 or more dispensed prescriptions on and 90 days after date of surgery (Q1) and subsequently 1 or more dispensed prescriptions 91-180 days after surgery (Q2). Preoperative opioid use was defined as 1 or more dispensed prescriptions 90 days before surgery. Logistic regression models were used to estimate risk factors for prolonged opioid use. RESULTS: We included 5,660 patients. Postoperatively 1,584 (28%) patients were dispensed 1 or more prescriptions in Q1 and Q2 and were classified as prolonged opioid users. Among the 2,037 preoperative opioid users and the 3,623 non-opioid users, 1,201 (59%) and 383 (11%) respectively were classified as prolonged users. Preoperative opioid use, female sex, alcohol abuse, previous surgery, high Charlson Comorbidity index, and preoperative use of either antidepressants, antipsychotics, or benzodiazepines were associated with increased risk of prolonged opioid use. CONCLUSION: The incidence of prolonged opioid use was 28%. Preoperative use of opioids was the strongest risk factor for prolonged opioid use, but several other risk factors were identified for prolonged opioid use.

High-resolution epidemiological landscape from ~290,000 SARS-CoV-2 genomes from Denmark.

Vast amounts of pathogen genomic, demographic and spatial data are transforming our understanding of SARS-CoV-2 emergence and spread. We examined the drivers of molecular evolution and spread of 291,791 SARS-CoV-2 genomes from Denmark in 2021. With a sequencing rate consistently exceeding 60%, and up to 80% of PCR-positive samples between March and November, the viral genome set is broadly whole-epidemic representative. We identify a consistent rise in viral diversity over time, with notable spikes upon the importation of novel variants (e.g., Delta and Omicron). By linking genomic data with rich individual-level demographic data from national registers, we find that individuals aged  < 15 and  > 75 years had a lower contribution to molecular change (i.e., branch lengths) compared to other age groups, but similar molecular evolutionary rates, suggesting a lower likelihood of introducing novel variants. Similarly, we find greater molecular change among vaccinated individuals, suggestive of immune evasion. We also observe evidence of transmission in rural areas to follow predictable diffusion processes. Conversely, urban areas are expectedly more complex due to their high mobility, emphasising the role of population structure in driving virus spread. Our analyses highlight the added value of integrating genomic data with detailed demographic and spatial information, particularly in the absence of structured infection surveys.

Incidence and survival of multiply revised knee arthroplasties in Denmark 1998-2021: a nationwide register-based study.

PURPOSE: The primary aim of our study was to identify the absolute incidence and implant survival of multiply revised knee arthroplasties based on nationwide register data. The secondary aim was to determine the change in the absolute incidence and implant survival of multiply revised knee arthroplasties Methods: We performed a retrospective observational study of primary knee arthroplasties using several nationwide Danish registers. All primary knee arthroplasties performed in Denmark from 1998 to 2021 were identified. From these primary arthroplasties, revision procedures were identified. Kaplan-Meier plots were used in survival analysis to estimate the likelihood of implant survival. RESULTS: 161,384 primary knee arthroplasties and their revisions performed between 1998 and 2021 were identified; of 13,786 (8.5%) revisions there were 10,638 1st revisions, 2,148 2nd revisions, 624 3rd revisions, 223 4th revisions, and 153 procedures that had been revised more than 4 times. The 10-year revision-free survival of primary arthroplasties was 92.3% (95% confidence interval [CI] 92.2-92.5). First-time revisions had a 10-year revision-free survival of 75.9% (CI 74.9-76.9). The 10-year survival of second- and third-time revisions was 65.1% (CI 62.6-67.6) and 57.8% (CI 53.4-62.5), respectively. The 10-year implant survival probabilities of primary knee arthroplasties were 91.4% in 1998-2009 and 93.3% in 2010-2021 (difference 2.2%). The 10-year implant survival probabilities of 1st revisions were 77% in 1998-2009 and 75% in 2010-2021 (difference -2.4%). CONCLUSION: We found that 0.3% of all primary knee arthroplasties resulted in 3 or more revisions. The implant survival decreased for each consecutive revision, with almost half of the 3rd revisions being re-revised within 10 years. The 10-survival of the primary implant was higher in 2010-2021, and the 10-year survival of the 1st revision was higher in 1998-2009.

Risk of serious adverse events after primary shoulder replacement: development and external validation of a prediction model using linked national data from England and Denmark.

BACKGROUND: Despite a rising rate of serious medical complications after shoulder replacement surgery, there are no prediction models in widespread use to guide surgeons in identifying patients at high risk and to provide patients with personalised risk estimates to support shared decision making. Our aim was to develop and externally validate a prediction model for serious adverse events within 90 days of primary shoulder replacement surgery. METHODS: Linked data from the National Joint Registry, National Health Service Hospital Episode Statistics Admitted Patient Care of England, and Civil Registration Mortality databases and Danish Shoulder Arthroplasty Registry and National Patient Register were used for our modelling study. Patients aged 18-100 years who had a primary shoulder replacement between April 1, 2012, and Oct 2, 2020, in England, and April 1, 2012, and Oct 2, 2018, in Denmark, were included. We developed a multivariable logistic regression model using the English dataset to predict the risk of 90-day serious adverse events, which were defined as medical complications requiring admission to hospital and all-cause death. We undertook internal validation using bootstrapping, and internal-external cross-validation across different geographical regions of England. The English model was externally validated on the Danish dataset. FINDINGS: Data for 40 631 patients undergoing primary shoulder replacement (mean age 72·5 years [SD 9·9]; 28 709 [70·7%] women and 11 922 [29·3%] men) were used for model development, of whom 2270 (5·6%) had a 90-day serious adverse event. On internal validation, the model had a C-statistic of 0·717 (95% CI 0·707-0·728) and was well calibrated. Internal-external cross-validation showed consistent model performance across all regions in England. Upon external validation on the Danish dataset (n=6653; mean age 70·5 years [SD 10·3]; 4503 [67·7%] women and 2150 [32·3%] men), the model had a C-statistic of 0·750 (95% CI 0·723-0·776). Decision curve analysis showed clinical utility, with net benefit across all risk thresholds. INTERPRETATION: This externally validated prediction model uses commonly available clinical variables to accurately predict the risk of serious medical complications after primary shoulder replacement surgery. The model is generalisable and applicable to most patients in need of a shoulder replacement. Its use offers support to clinicians and could inform and empower patients in the shared decision-making process. FUNDING: National Institute for Health and Care Research and the Department of Orthopaedic Surgery, Herlev and Gentofte Hospital, Denmark.