| 1. |
- Aslam, Tayyba N., et al.
(författare)
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A survey of preferences for respiratory support in the intensive care unit for patients with acute hypoxaemic respiratory failure
- 2023
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Ingår i: Acta Anaesthesiologica Scandinavica. - : WILEY. - 0001-5172 .- 1399-6576. ; 67:10, s. 1383-1394
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Tidskriftsartikel (refereegranskat)abstract
- BackgroundWhen caring for mechanically ventilated adults with acute hypoxaemic respiratory failure (AHRF), clinicians are faced with an uncertain choice between ventilator modes allowing for spontaneous breaths or ventilation fully controlled by the ventilator. The preferences of clinicians managing such patients, and what motivates their choice of ventilator mode, are largely unknown. To better understand how clinicians preferences may impact the choice of ventilatory support for patients with AHRF, we issued a survey to an international network of intensive care unit (ICU) researchers.MethodsWe distributed an online survey with 32 broadly similar and interlinked questions on how clinicians prioritise spontaneous or controlled ventilation in invasively ventilated patients with AHRF of different severity, and which factors determine their choice.ResultsThe survey was distributed to 1337 recipients in 12 countries. Of these, 415 (31%) completed the survey either fully (52%) or partially (48%). Most respondents were identified as medical specialists (87%) or physicians in training (11%). Modes allowing for spontaneous ventilation were considered preferable in mild AHRF, with controlled ventilation considered as progressively more important in moderate and severe AHRF. Among respondents there was strong support (90%) for a randomised clinical trial comparing spontaneous with controlled ventilation in patients with moderate AHRF.ConclusionsThe responses from this international survey suggest that there is clinical equipoise for the preferred ventilator mode in patients with AHRF of moderate severity. We found strong support for a randomised trial comparing modes of ventilation in patients with moderate AHRF.
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| 2. |
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| 3. |
- Denby, Bruce, et al.
(författare)
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ESTIMATING DOMESTIC WOOD BURNING EMISSIONS OF PARTICULATE MATTER IN TWO NORDIC CITIES BY COMBINING AMBIENT AIR OBSERVATIONS WITH RECEPTOR AND DISPERSION MODELS
- 2010
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Ingår i: Chemical Industry and Chemical Engineering Quarterly. - 1451-9372. ; 16:3, s. 237-241
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Tidskriftsartikel (refereegranskat)abstract
- The major emission source of primary PM2 (5) in many Nordic countries is wood burning for domestic heating Though direct measurements of wood burning emissions are possible under controlled conditions, emission inventories for urban scale domestic heating are difficult to calculate and remain uncertain As an alternative method for estimating these emissions, this paper makes use of ambient air measurements chemical analysis of filter samples receptor models, dispersion models, and simple inverse modelling methods to infer the emission strengths A comparison of dispersion models with receptor models indicates that the dispersion models tend to overestimate the contribution from wood burning The inverse modelling results are found to agree with those from the receptor modelling Though both the receptor and inverse modelling point to an overestimation of the wood burning emissions of PM2 (5), it is not possible to assign this solely to errors in the emissions inventory as a dispersion model error can be significant It is recommended to improve plume rise and urban canopy meteorological descriptions in the dispersion models before these models are of sufficient quality to allow quantitative assessments of emission inventories
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| 4. |
- Enqvist, Monika, et al.
(författare)
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Systemic and Intra-Nodal Activation of NK Cells After Rituximab Monotherapy for Follicular Lymphoma.
- 2019
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Ingår i: Frontiers in Immunology. - : Frontiers Media SA. - 1664-3224. ; 10
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Tidskriftsartikel (refereegranskat)abstract
- Monotherapy with the anti-CD20 monoclonal antibody rituximab can induce complete responses (CR) in patients with follicular lymphoma (FL). Resting FcRγIII+ (CD16+) natural killer (NK) cells respond strongly to rituximab-coated target cells in vitro. Yet, the contribution of NK cells in the therapeutic effect in vivo remains unknown. Here, we followed the NK cell repertoire dynamics in the lymph node and systemically during rituximab monotherapy in patients with FL. At baseline, NK cells in the tumor lymph node had a naïve phenotype albeit they were more differentiated than NK cells derived from control tonsils as determined by the frequency of CD56dim NK cells and the expression of killer cell immunoglobulin-like receptors (KIR), CD57 and CD16. Rituximab therapy induced a rapid drop in NK cell numbers coinciding with a relative increase in the frequency of Ki67+ NK cells both in the lymph node and peripheral blood. The Ki67+ NK cells had slightly increased expression of CD16, CD57 and higher levels of granzyme A and perforin. The in vivo activation of NK cells was paralleled by a temporary loss of in vitro functionality, primarily manifested as decreased IFNγ production in response to rituximab-coated targets. However, patients with pre-existing NKG2C+ adaptive NK cell subsets showed less Ki67 upregulation and were refractory to the loss of functionality. These data reveal variable imprints of rituximab monotherapy on the NK cell repertoire, which may depend on pre-existing repertoire diversity.
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| 5. |
- Grimvall, Anders, et al.
(författare)
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Semiparametric smoothers for trend assessment of multiple time series of environmental quality data
- 2008
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Ingår i: Environmetrics. - 1180-4009 .- 1099-095X.
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Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)abstract
- Multiple time series of environmental quality data with similar, but not necessarily identical, trends call for multivariate methods for trend detection and adjustment for covariates. Here, we show how an additive model in which the multivariate trend function is specified in a nonparametric fashion (and the adjustment for covariates is based on a parametric expression) can be used to estimate how the human impact on an ecosystem varies with time and across components of the observed vector time series. More specifically, we demonstrate how a roughness penalty approach can be utilized to impose different types of smoothness on the function surface that describes trends in environmental quality as a function of time and vector component. Compared to other tools used for this purpose, such as Gaussian smoothers and thin plate splines, an advantage of our approach is that the smoothing pattern can easily be tailored to different types of relationships between the vector components. We give explicit roughness penalty expressions for data collected over several seasons or representing several classes on a linear or circular scale. In addition, we define a general separable smoothing method. A new resampling technique that preserves statistical dependencies over time and across vector components enables realistic calculations of confidence and prediction intervals.
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| 6. |
- Kauppila, Joonas H, et al.
(författare)
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Gastrectomy compared to oesophagectomy for Siewert II and III gastro-oesophageal junctional cancer in relation to resection margins, lymphadenectomy and survival
- 2017
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Ingår i: Scientific Reports. - Stockholm : Karolinska Institutet, Dept of Molecular Medicine and Surgery. - 2045-2322.
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Tidskriftsartikel (refereegranskat)abstract
- It is unclear whether gastrectomy or oesophagectomy offer better outcomes for gastro-oesophageal junction (GOJ) cancer. A total of 240 patients undergoing total gastrectomy (n = 85) or oesophagectomy (n = 155) for Siewert II-III GOJ adenocarcinoma were identified from a Swedish prospective population-based nationwide cohort. The surgical approaches were compared in relation to non-radical resection margins (main outcome) using multivariable logistic regression, providing odds ratios (ORs) and 95% confidence intervals (CIs), mean number of removed lymph nodes with standard deviation (SD) using ANCOVA, assessing mean differences and 95% CIs, and 5-year mortality using Cox regression estimating hazard ratios (HRs) and 95% CIs. The models were adjusted for age, sex, comorbidity, tumour stage, and surgeon volume. The non-radical resection rate was 15% for gastrectomy and 14% for oesophagectomy, and the adjusted OR was 1.61 (95% CI 0.68-3.83). The mean number of lymph nodes removed was 14.2 (SD +/- 9.6) for gastrectomy and 14.2 (SD +/- 10.4) for oesophagectomy, with adjusted mean difference of 2.4 (95% CI-0.2-5.0). The 5-year mortality was 76% following gastrectomy and 75% following oesophagectomy, with adjusted HR = 1.07 (95% CI 0.78-1.47). Gastrectomy and oesophagectomy for Siewert II or III GOJ cancer seem comparable regarding tumour-free resection margins, lymph nodes removal, and 5-year survival.
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| 7. |
- Kauppila, Joonas H, et al.
(författare)
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Neoadjuvant therapy in relation to lymphadenectomy and resection margins during surgery for oesophageal cancer
- 2018
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Ingår i: Scientific Reports. - Stockholm : Karolinska Institutet, Dept of Molecular Medicine and Surgery. - 2045-2322.
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Tidskriftsartikel (refereegranskat)abstract
- It is unclear whether gastrectomy or oesophagectomy offer better outcomes for gastro-oesophageal junction (GOJ) cancer. A total of 240 patients undergoing total gastrectomy (n = 85) or oesophagectomy (n = 155) for Siewert II-III GOJ adenocarcinoma were identified from a Swedish prospective population-based nationwide cohort. The surgical approaches were compared in relation to non-radical resection margins (main outcome) using multivariable logistic regression, providing odds ratios (ORs) and 95% confidence intervals (CIs), mean number of removed lymph nodes with standard deviation (SD) using ANCOVA, assessing mean differences and 95% CIs, and 5-year mortality using Cox regression estimating hazard ratios (HRs) and 95% CIs. The models were adjusted for age, sex, comorbidity, tumour stage, and surgeon volume. The non-radical resection rate was 15% for gastrectomy and 14% for oesophagectomy, and the adjusted OR was 1.61 (95% CI 0.68-3.83). The mean number of lymph nodes removed was 14.2 (SD +/- 9.6) for gastrectomy and 14.2 (SD +/- 10.4) for oesophagectomy, with adjusted mean difference of 2.4 (95% CI-0.2-5.0). The 5-year mortality was 76% following gastrectomy and 75% following oesophagectomy, with adjusted HR = 1.07 (95% CI 0.78-1.47). Gastrectomy and oesophagectomy for Siewert II or III GOJ cancer seem comparable regarding tumour-free resection margins, lymph nodes removal, and 5-year survival.
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| 8. |
- Libiseller, Claudia, 1975-, et al.
(författare)
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Power Simulations using Data generated by Process-based Deterministic Models
- 2004
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Ingår i: COMPSTAT 2004,2004.
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- Power analysis is an integral part of statistical hypothesis testing, and, when neither exactpower computations nor reasonable approximations are feasible, Monte Carlo simulations providea viable alternative. However, generating data for such simulations is often an intricate task, especially when the hypothesis testing is based on non-normal multivariate data withcomplex dependencies. Here, we show how process-based deterministic models can be employed to generate data with adequate statistical dependencies for realistic power simulations. In particular, we usedthe Integrated Nitrogen in Catchments INCA model to produce bivariate time series ofnitrogen concentration and water discharge data that included plausible temporal trends andrealistic cross-correlations, seasonal patterns, and memory effects. The random variation in thegenerated data was achieved by running the INCA model with various sets of weather data that were obtained by block resampling from a given time series of observed air temperatureand precipitation data. The assortment of temporal trends was created by altering the anthropogenic input of nitrogen to the catchment under consideration.Two tests for temporal trends in nitrogen concentration were compared: i a partial Mann-Kendall test in which water discharge was treated as a covariate; ii a two-stage procedurein which we first used a semi-parametric regression technique to remove the impact of natural fluctuations in water discharge, and we subsequently applied an ordinary Mann-Kendall testto the obtained residuals. Our simulations demonstrated that the two tests had comparablepower, but also that they involved empirical significance levels that were much higher than the nominal levels, possibly due to substantial serial dependence in the data.
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| 9. |
- Maret-Ouda, John, et al.
(författare)
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Association between laparoscopic antireflux surgery and recurrence of gastroesophageal reflux
- 2017
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Ingår i: Journal of the American Medical Association. - Stockholm : Karolinska Institutet, Dept of Molecular Medicine and Surgery. - 0098-7484 .- 1538-3598.
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Tidskriftsartikel (refereegranskat)abstract
- IMPORTANCE: Cohort studies, mainly based on questionnaires and interviews, have reported high rates of reflux recurrence after antireflux surgery, which may have contributed to a decline in its use. Reflux recurrence after laparoscopic antireflux surgery has not been assessed in a long-term population-based study of unselected patients. OBJECTIVES: To determine the risk of reflux recurrence after laparoscopic antireflux surgery and to identify risk factors for recurrence. DESIGN AND SETTING: Nationwide population-based retrospective cohort study in Sweden between January 1, 2005, and December 31, 2014, based on all Swedish health care and including 2655 patients who underwent laparoscopic antireflux surgery according to the Swedish Patient Registry. Their records were linked to the Swedish Causes of Death Registry and Prescribed Drug Registry. EXPOSURES: Primary laparoscopic antireflux surgery due to gastroesophageal reflux disease in adults (>18 years). MAIN OUTCOMES AND MEASURES: The outcomewas recurrence of reflux, defined as use of antireflux medication (proton pump inhibitors or histamine2 receptor antagonists for >6 months) or secondary antireflux surgery. Multivariable Cox regression was used to assess risk factors for reflux recurrence. RESULTS: Among all 2655 patients who underwent antireflux surgery (median age, 51.0 years; interquartile range, 40.0-61.0 years; 1354 men [51.0%]) and were followed up for a median of 5.6 years, 470 patients (17.7%) had reflux recurrence; 393 (83.6%) received long-term antireflux medication and 77 (16.4%) underwent secondary antireflux surgery. Risk factors for reflux recurrence included female sex (hazard ratio [HR], 1.57 [95%CI, 1.29-1.90]; 286 of 1301 women [22.0%] and 184 of 1354 men [13.6%] had recurrence of reflux), older age (HR, 1.41 [95%CI, 1.10-1.81] for age 61 years compared with 45 years; recurrence among 156 of 715 patients and 133 of 989 patients, respectively), and comorbidity (HR, 1.36 [95%CI, 1.13-1.65] for Charlson comorbidity index score 1 compared with 0; recurrence among 180 of 804 patients and 290 of 1851 patients, respectively). Hospital volume of antireflux surgery was not associated with risk of reflux recurrence (HR, 1.09 [95%CI, 0.77-1.53] for hospital volume 24 surgeries compared with 76 surgeries; recurrence among 38 of 266 patients [14.3%] and 271 of 1526 patients [17.8%], respectively). CONCLUSIONS AND RELEVANCE: Among patients who underwent primary laparoscopic antireflux surgery, 17.7%experienced recurrent gastroesophageal reflux requiring long-term medication use or secondary antireflux surgery. Risk factors for recurrence were older age, female sex, and comorbidity. Laparoscopic antireflux surgery was associated with a relatively high rate of recurrent gastroesophageal reflux disease requiring treatment, diminishing some of the benefits of the operation.
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| 10. |
- Maret-Ouda, John, et al.
(författare)
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Cohort profile : the Nordic antireflux surgery cohort (NordASCo)
- 2017
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Ingår i: BMJ Open. - Stockholm : Karolinska Institutet, Dept of Molecular Medicine and Surgery. - 2044-6055.
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Tidskriftsartikel (refereegranskat)abstract
- PURPOSE: To describe a newly created all-Nordic cohort of patients with gastro-oesophageal reflux disease (GORD), entitled the Nordic Antireflux Surgery Cohort (NordASCo), which will be used to compare participants having undergone antireflux surgery with those who have not regarding risk of cancers, other diseases and mortality. PARTICIPANTS: Included were individuals with a GORD diagnosis recorded in any of the nationwide patient registries in the Nordic countries (Denmark, Finland, Iceland, Norway and Sweden) in 1964-2014 (with various start and end years in different countries). Data regarding cancer, other diseases and mortality were retrieved from the nationwide registries for cancer, patients and causes of death, respectively. FINDINGS TO DATE: The NordASCo includes 945 153 individuals with a diagnosis of GORD. Of these, 48 433 (5.1%) have undergone primary antireflux surgery. Median age at primary antireflux surgery ranged from 47 to 52 years in the different countries. The coding practices of GORD seem to have differed between the Nordic countries. FUTURE PLANS: The NordASCo will initially be used to analyse the risk of developing known or potential GORD-related cancers, that is, tumours of the oesophagus, stomach, larynx, pharynx and lung, and to evaluate the mortality in the short-term and long-term perspectives. Additionally, the cohort will be used to evaluate the risk of non-malignant respiratory conditions that might be caused by aspiration of gastric contents.
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| 11. |
- Maret-Ouda, John, et al.
(författare)
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Nordic registry-based cohort studies : possibilities and pitfalls when combining Nordic registry data
- 2017
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Ingår i: Scandinavian Journal of Public Health. - Stockholm : Karolinska Institutet, Dept of Molecular Medicine and Surgery. - 1403-4948 .- 1651-1905.
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Tidskriftsartikel (refereegranskat)abstract
- Aims: All five Nordic countries (Denmark, Finland, Iceland, Norway, and Sweden) have nationwide registries with similar data structure and validity, as well as personal identity numbers enabling linkage between registries. These resources provide opportunities for medical research that is based on large registry-based cohort studies with long and complete follow-up. This review describes practical aspects, opportunities, and challenges encountered when setting up all-Nordic registry-based cohort studies. Methods: Relevant articles describing registries often used for medical research in the Nordic countries were retrieved. Further, our experiences of conducting this type of study, including planning, acquiring permissions, data retrieval, and data cleaning and handling, and the possibilities and challenges we have encountered, are described. Results: Combining data from the Nordic countries makes it possible to create large and powerful cohorts. The main challenges include obtaining all permissions within each country, usually in the local language, and to retrieve the data. These challenges emphasise the importance of having experienced collaborators within each country. Following the acquisition of data, data management requires the understanding of differences between the variables to be used in the various countries. A concern is the long time required between initiation and completion. Conclusions: Nationwide Nordic registries can be combined into cohorts with high validity and statistical power, but the considerable expertise, workload, and time required to complete such cohorts should not be underestimated.
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| 12. |
- Ness-Jensen, Eivind, et al.
(författare)
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All-cause and cancer-specific mortality in GORD in a population-based cohort study (the HUNT study)
- 2018
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Ingår i: Gut. - Stockholm : Karolinska Institutet, Dept of Molecular Medicine and Surgery. - 0017-5749 .- 1468-3288.
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Tidskriftsartikel (refereegranskat)abstract
- OBJECTIVE: Gastro-oesophageal reflux is a public health concern which could have associated oesophageal complications, including adenocarcinoma, and possibly also head-and-neck and lung cancers. The aim of this study was to test the hypothesis that reflux increases all-cause and cancer-specific mortalities in an unselected cohort. DESIGN: The Nord-Trondelag health study (HUNT), a Norwegian population-based cohort study, was used to identify individuals with and without reflux in 1995-1997 and 2006-2008, with follow-up until 2014. All-cause mortality and cancer-specific mortality were assessed from the Norwegian Cause of Death Registry and Cancer Registry. Multivariable Cox regression was used to calculate HRs with 95% CIs for mortality with adjustments for potential confounders. RESULTS: We included 4758 participants with severe reflux symptoms and 51 381 participants without reflux symptoms, contributing 60 323 and 747 239 person-years at risk, respectively. Severe reflux was not associated with all-cause mortality, overall cancer-specific mortality or mortality in cancer of the head-and-neck or lung. However, for men with severe reflux a sixfold increase in oesophageal adenocarcinoma-specific mortality was found (HR 6.09, 95% CI 2.33 to 15.93) and the mortality rate was 0.27 per 1000 person-years. For women, the corresponding mortality was not significantly increased (HR 3.68, 95% CI 0.88 to 15.27) and the mortality rate was 0.05 per 1000 person-years. CONCLUSIONS: Individuals with severe reflux symptoms do not seem to have increased all-cause mortality or overall cancer-specific mortality. Although the absolute risk is small, individuals with severe reflux symptoms have a clearly increased oesophageal adenocarcinoma-specific mortality.
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| 13. |
- Norberg, Pernilla, et al.
(författare)
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Does quantitative lung SPECT detect lung abnormalities earlier than lung function tests? : Results of a pilot study
- 2014
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Ingår i: EJNMMI Research. - : Springer Berlin/Heidelberg. - 2191-219X. ; 4:39, s. 1-12
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Tidskriftsartikel (refereegranskat)abstract
- Background: Heterogeneous ventilation in lungs of allergic individuals, cigarette smokers, asthmatics and chronic obstructive pulmonary disease (COPD) patients has been demonstrated using imaging modalities such as PET, MR and SPECT. These individuals suffer from narrow and/or closed airways to various extents. By calculating regional heterogeneity in lung ventilation SPECT images as the coefficient of variation (CV) in small elements of the lung, heterogeneity maps and CV-frequency curves can be generated and used to quantitatively measure heterogeneity. This work explores the potential to use such measurements to detect mild ventilation heterogeneities in lung healthy subjects.Method: Fourteen healthy subjects without documented lung disease or respiratory symptoms, and two patients with documented airway disease, inhaled on average approximately 90 MBq 99mTc-Technegas immediately prior to the 20 min SPECT acquisition. Variation in activity uptake between subjects was compensated for in resulting CV values. The area under the compensated CV frequency curve (AUC), for CV values greater than a threshold value CVT, AUC(CV> CVT), was used as the measure of ventilation heterogeneity.Results: Patients with lung function abnormalities, according to lung function tests, generated higher AUC(CV>20%) values compared to healthy subjects (p=0.006). Strong linear correlations with the AUC(CV>20%) values were found for age (p=0.006) and height (p=0.001). These demonstrated that ventilation heterogeneities increased with age and that they depend on lung size. Strong linear correlations were found for the lung function value related to indices of airway closure/air trapping, RV/TLC (p=0.009), and DLCOc (p=0.009), a value partly related to supposed ventilation/perfusion mismatch. These findings support the association between conventional lung function tests and the AUC(CV>20%) value.Conclusions: Among the healthy subjects there is a group with increased AUC(CV>20%) values, but with normal lung function tests, which implies that it might be possible to differentiate ventilation heterogeneities earlier in a disease process than by lung function tests.
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| 14. |
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| 15. |
- Rendek, Zlatica, et al.
(författare)
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Effect of oral diclofenac intake on faecal calprotectin
- 2016
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Ingår i: Scandinavian Journal of Gastroenterology. - : TAYLOR & FRANCIS LTD. - 0036-5521 .- 1502-7708. ; 51:1, s. 28-32
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Tidskriftsartikel (refereegranskat)abstract
- Background. NSAIDs are a known source of increased faecal calprotectin (FC) levels. Currently, there is a lack of knowledge about how long it takes for an increased FC level to return to normal after NSAID intake. Objective. The aim was to investigate how oral diclofenac intake affects FC levels and assess how long it takes for an increased FC level to return to normal after oral diclofenac intake. Material and methods. Thirty healthy volunteers received diclofenac 50 mg three times daily for 14 days. Participants provided a stool sample on Days 0, 2, 4, 7, 14 during intake and Days 17, 21, 28 after discontinuation. FC levels were then followed at 7-day intervals until normalization. Results. During diclofenac intake, eight participants (27%) had FC levels exceeding the upper limit of normal (median, 76 mu g/g; range, 60-958 mu g/g), corresponding to 8.3% of measurements. FC was not constantly increased and became normal in most participants during diclofenac intake. FC levels were on average significantly higher during intake (M = 9.5, interquartile range (IQR) = 13.4) than on baseline (M = 7.5, IQR = 0.0), p = 0.003. After discontinuation, two participants had increased FC on Days 17 and 21, respectively. No significant differences in FC levels were found between baseline and measurements after discontinuation. Two weeks after discontinuation, all participants had normal FC levels. Conclusions. Short-term oral diclofenac intake is associated with increased FC levels. However, the likelihood of an increased test result is low. Our results suggest that 2 weeks of diclofenac withdrawal is sufficient to get an uninfluenced FC test result.
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| 16. |
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| 17. |
- Thorell, Lars-Håkan, 1943-, et al.
(författare)
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Improper study design precludes valid effect estimates in important suicide prevention research
- 2019
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Ingår i: International Journal of Methods in Psychiatric Research. - : John Wiley & Sons. - 1049-8931 .- 1557-0657. ; 28:3
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Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)abstract
- The observational study design for estimating accuracy of diagnostic tests for suicide risk in clinical work is not ideal, due to the effects of directed suicide prevention to the high-risk group. This is an example of the confounding by indication and protopathic bias, which lead to misinterpretation of the accuracy terms sensitivity and specificity. The simple arithmetic mechanism presented here, forces the conclusion that the accuracy estimates sensitivity and specificity, applied in open prospective trials of surmised diagnostic tests for suicide risk, cannot be normally interpreted as accuracy estimators. Further, the related concept "prediction of suicide" is shown to be fundamentally illogical and should not be used in the present context. All these statements reveal a far-reaching problem within the suicide prevention research: Conclusions regarding the usefulness of diagnostic tests of suicide risk in the vast previous research since decades deserve reinterpretation. Diagnostic tests per se, can possess highly qualitative properties in estimating important suicidological aspects regarding a patient, but, when studied in an open design study, it cannot be demonstrated. This problem concerns rating scales and any biological and psychological tests in medicine, when confounding factors, for example, suicide prevention, influence the outcome because of the test result per se.
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| 18. |
- Wahlin, Karl, et al.
(författare)
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Estimating artificial level shifts in the presence of smooth trends
- 2008
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Ingår i: Environmental Monitoring and Assessment. - 0167-6369.
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Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)abstract
- Changes in observational data over time can be severely distorted by errors in measurements, sampling, or reporting. Here, we show how smooth trends in vector time series can be separated from one or two abrupt level shifts that occur simultaneously in all coordinates. Trends are modelled nonparametrically, whereas abrupt changes and the impact of covariates are modelled parametrically. The model is estimated using a backfitting algorithm in which estimation of smooth trends is alternated with estimation of regression coefficients for covariates and assessment of sudden level shifts. The proposed method is adaptive in the sense that the degree of smoothing over time and across coordinates is controlled by a roughness penalty and cross-validation procedure that automatically identifies the interdependence of the analysed data. Furthermore, it uses a resampling technique that can accommodate correlated error terms in the assessment of the uncertainty of both smooth trends and discontinuities. The method is applied to water quality data from Swedish national monitoring programmes to illustrate how known discontinuities can be quantified and how previously unrecognized discontinuities can be detected.
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| 19. |
- Wahlin, Karl, et al.
(författare)
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Reduced Models of the Retention of Nitrogen in Catchments
- 2004
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Ingår i: Proceedings of the International Environmental Modelling and Software Society Conference (iEMSs), 14-17 June, Osnabrück, Germany. ; , s. 1081-1086
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Konferensbidrag (refereegranskat)abstract
- Process-oriented models of the retention of nitrogen in catchments are by necessity rather complex. We introduced several types of ensemble runs that can provide informative summaries of meteorologically normalised model outputs and also clarify the extent to which such outputs are related to various model parameters. Thereafter we employed this technique to examine policy-relevant outputs of the catchment model INCA-N. In particular, we examined how long it will take for changes in the application of fertilisers on cultivated land to affect the predicted riverine loads of nitrogen. The results showed that the magnitude of the total intervention effect was influenced mainly by the parameters governing the turnover of nitrogen in soil, whereas the temporal distribution of the water quality response was determined primarily by the hydromechanical model parameters. This raises the question of whether the soil nitrogen processes included in the model are elaborate enough to correctly explain the widespread observations of slow water quality responses to changes in agricultural practices.
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| 20. |
- Wahlin, Karl, et al.
(författare)
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Roadmap for assessing regional trends in groundwater quality
- 2010
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Ingår i: Environmental Monitoring and Assessment. - : Springer Science Business Media. - 0167-6369 .- 1573-2959. ; 165:1-4, s. 217-231
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Tidskriftsartikel (refereegranskat)abstract
- Assessing regional trends in groundwater quality can be a difficult task. Data are often scattered in space and time, and the inertia of groundwater systems can create natural, seemingly persistent changes in concentration that are difficult to separate from anthropogenic trends. Here, we show how statistical methods and software for joint analysis of multiple time series can be integrated into a roadmap for trend analysis and critical examination of data quality. Ordinary and partial Mann-Kendall (MK) tests for monotonic trends and semiparametric smoothers for multiple time series constitute the cornerstones of our procedure. The MK tests include a simple and easily implemented method to correct for serial dependence, and the associated software is designed to enable convenient handling of numerous data series and to accommodate covariates and nondetects. The semiparametric smoothers are intended to facilitate detection of synchronous changes in a network of stations. A study of Swedish groundwater quality data revealed true upward trends in acid-neutralizing capacity (ANC) and downward trends in sulphate, but also a misleading shift in alkalinity level that would have been difficult to detect if the time series had been analysed separately.
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| 21. |
- Wahlin, Karl, 1978-
(författare)
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Roadmap for trend detection and assessment of data quality
- 2008
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Regular measurements of the state of the environment constitute a cornerstone of environmental management. Without the support of long time series of reliable data, we would know much less about changes that occur in the environment and their causes. The present research aimed to explore how improved techniques for data analysis can help reveal flawed data and extract more information from environmental monitoring programmes. Based on our results, we propose that the organization of such monitoring should be transformed from a system for measuring and collecting data to an information system where resources have been reallocated to data analysis. More specifically, this thesis reports improved methods for joint analysis of trends in multiple time series and detection of artificial level shifts in the presence of smooth trends. Furthermore, special consideration is given to methods that automatically detect and adapt to the interdependence of the collected data. The current work resulted in a roadmap describing the process of proceeding from a set of observed concentrations to arrive at conclusions about the quality of the data and existence of trends therein. Improvements in existing software accompanied the development of new statistical procedures.
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| 22. |
- Wahlin, Karl, 1978-, et al.
(författare)
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Uncertainty in water quality data and its implications for trend detection : lessons from Swedish environmental data
- 2008
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Ingår i: Environmental Science and Policy. - : Elsevier BV. - 1462-9011 .- 1873-6416. ; 11:2, s. 115-124
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Tidskriftsartikel (refereegranskat)abstract
- The demands on monitoring systems have gradually increased, and interpretation of the data is often a matter of controversy. As an example of this, we investigated water quality monitoring and the eutrophication issue in Sweden. Our results demonstrate that powerful statistical tools for trend analysis can reveal flaws in the data and lead to new and revised interpretations of environmental data. In particular, we found strong evidence that long-term trends in measured nutrient concentrations can be more extensively influenced by changes in sampling and laboratory practices than by actual changes in the state of the environment. On a more general level, our findings raise important questions regarding the need for new paradigms for environmental monitoring and assessment. Introduction of a system in which conventional quality assurance is complemented with thorough statistical follow-up of reported values would represent a first step towards recognizing that environmental monitoring and assessment should be transformed from being a system for sampling and laboratory analyses into a system for interpreting information to support policy development.
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| 23. |
- Wang, Qiao-Li, et al.
(författare)
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Global time trends in the incidence of esophageal squamous cell carcinoma
- 2018
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Ingår i: Clinical Epidemiology. - Stockholm : Karolinska Institutet, Dept of Molecular Medicine and Surgery. - 1179-1349.
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Tidskriftsartikel (refereegranskat)abstract
- Background & Aims: Esophageal squamous cell carcinoma (ESCC) is the dominant histological type of esophageal cancer worldwide (90%). We aimed to provide an update of the global temporal trends in the incidence of ESCC. Methods: Incidence data for ESCC were collected from 30 well-established cancer registries from 20 countries in Europe, Northern America, Australia, or Asia in 1970-2015. Time trends in annual age-standardized incidence rates of ESCC were assessed using joinpoint analysis and log-linear regression. Age-period-cohort analysis was used to estimate the influence of age, calendar-period, and birth-cohort on the observed time trends in incidence. Results: The age-standardized incidence rates of ESCC varied more than 8-fold in men and 7-fold in women across populations. In 2012, the highest rate in men was observed in Japan, Nagasaki (9.7/100 000 person-years) and women in Scotland (2.7/100 000 person-years). In men, the incidence decreased globally during the study period, as well as during the last few years. In women, the incidence increased in Japan (3 regions), the Netherlands, New Zealand, Norway, and Switzerland, while it was stable or decreased in other populations. Among ethnical groups in the United States, black men and women had more pronounced decreases in incidence than other groups. Generally, birth-cohort effects were stronger determinants of incidence trends than calendar-period effects. Conclusions: In men, the global ESCC incidence has decreased over time. In women, the incidence trends vary across populations, and the rates have increased in some countries. Changes in the prevalence of tobacco smoking and alcohol consumption may have contributed to these time trends.
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