Maastricht University
  • Maastricht, Netherlands
Recent publications
This chapter introduces the reader to the field of Memory Studies. It traces the emergence of memory as a topic of investigation and gives an overview of the development of the field. It highlights the main actors and institutions, describes the most influential debates that have shaped the field and illustrates the institutional structures that sustain it. In doing so, it argues that Memory Studies has started to display all the features characteristic of an established discipline.
Parkinson’s disease is a highly heterogeneous disorder, encompassing a complex spectrum of clinical presentation including motor, sleep, cognitive and neuropsychiatric symptoms. We aimed to investigate genome-wide DNA methylation networks in post-mortem Parkinson’s disease brain samples and test for region-specific association with common neuropsychiatric and cognitive symptoms. Of traits tested, we identify a co-methylation module in the substantia nigra with significant correlation to depressive symptoms and with ontological enrichment for terms relevant to neuronal and synaptic processes. Notably, expression of the genes annotated to the methylation loci present within this module are found to be significantly enriched in neuronal subtypes within the substantia nigra. These findings highlight the potential involvement of neuronal-specific changes within the substantia nigra with regard to depressive symptoms in Parkinson’s disease.
The purpose of the study was to investigate perceived determinants of physical activity (PA) maintenance following supervised exercise oncology rehabilitation and the acceptability of a remote coaching intervention during this period. A phenomenological qualitative study with semi-structured interviews was conducted. Nineteen participants (16 women, 3 men) were recruited from the intervention (n = 12) and control group (n = 7) of a randomized controlled trial on the effectiveness of remote coaching following hospital-based, supervised exercise oncology rehabilitation. Participants in the intervention group received a 6-month remote coaching intervention after completing the exercise program, aimed at stimulating PA maintenance. The interviews were based on the Capability, Opportunity, and Motivation model of Behaviour (COM-B model) and the framework of acceptability (TFA) and were coded using template analysis. Key themes regarding determinants of PA maintenance were self-efficacy, PA habits, accountability, physical complaints, and facilities. Remote coaching was perceived acceptable because it stimulated PA maintenance by offering a source of structure and social support and thereby increased accountability. Moreover, it improved confidence to perform PA, leading to increased levels of self-efficacy. The remote nature of the intervention was perceived as convenient by some of the participants, while others would have preferred additional physical appointments. Cancer survivors considered remote coaching acceptable to stimulate PA maintenance following supervised rehabilitation. Interventions should focus on increasing accountability, self-efficacy, forming habits, and helping cancer survivors to overcome barriers. The ability to maintain PA beyond supervised exercise oncology programs depends on many determinants. Remote coaching interventions have potential to target individually relevant determinants following exercise programs in cancer survivors.
Background Analysis of volatile organic compounds (VOCs) in exhaled breath has the potential to serve as an accurate diagnostic tool for gastro-intestinal diseases. Animal studies could be instrumental as a preclinical base and subsequent clinical translation to humans, as they are easier to standardize and better equipped to relate specific VOCs to metabolic and pathological processes. This review provides an overview of the study design, characteristics and methodological quality of previously published animal studies on analysis of exhaled breath in gastrointestinal and hepatic diseases. Guidelines are provided for standardization in study design and breath collection methods to improve comparability, avoid duplication of research and reduce discomfort of animals in future studies. Methods PubMed and Embase database were searched for animal studies using exhaled breath analysis to detect gastro-intestinal diseases. Risk of bias was assessed using the SYRCLE’s risk of bias tool for animal studies. Information on study design, standardization methods, animal models, breath collection methods and identified VOCs were extracted from the included studies. Results 10 studies were included (acute liver failure n = 1, non-alcoholic steatohepatitis n = 1, hepatic ischemia n = 2, mesenteric ischemia n = 2, sepsis and peritonitis n = 3, colitis n = 1). Rats were used in most of the studies. Exhaled breath was mostly collected using invasive procedures as tracheal cannulation or tracheostomy. Poor reporting on standardization, breath collection methods, analytical techniques, as well as heterogeneity of the studies, complicate comparison of the different studies. Conclusion Poor reporting of essential methodological details impaired comprehensive summarizing the various studies on exhaled breath in gastrointestinal and hepatic diseases. Potential pitfalls in study design, and suggestions for improvement of study design are discussed which, when applied, lead to consistent and generalizable results and a reduction in the use of laboratory animals. Refining the methodological quality of animal studies has the potential to improve subsequent clinical trial design.
Past corruption research at the individual level has mainly focused on demographics, personality, attitudes, or morality related variables. Until now, only a few studies have focused on the intra -individual psychological mechanisms of corruption. Building on normative decision-making theory, the present study attempts to shed further light on the internal mechanisms that lead to the decision that corruption is a viable path. Following an informed grounded theory approach, we conducted semi-structured interviews with 38 Indonesian prisoners who have been convicted of corruption. Guided by a multi-step decision-making process, including problem recognition, information search, and evaluation of the information, our results revealed unique insights into individuals’ considerations that led to corruption. We elaborate on interrelations between these stages and explore new forms of corrupt decision-making elements within this process. Theoretical implications for corruption research and the practical implications for anti-corruption programs of these findings are discussed.
The present study aims to develop, validate, and cross‐validate an instrument measuring three proactive social informal learning activities, namely feedback seeking, help seeking and information seeking. Prior research mainly focused on detecting or measuring the frequency of these seeking behaviours and did not consider whether the information, help or feedback that has been sought was also used. Furthermore, although these seeking behaviours were studied extensively in different research fields, the current study takes a learning perspective and interprets feedback, help and information seeking as learning activities. The questionnaire was completed by a convenient sample of 650 professionals working in higher education, consultancy, retail and food production. We performed an exploratory factor analysis ( N = 230 educators) to explore the structure of the questionnaire. This was followed by a confirmatory factor analysis ( N = 230 educators) to confirm the structure. Finally, we cross‐validated the questionnaire in a sample of business professionals ( N = 190) by testing for measurement invariance. The final questionnaire resulted in a five‐factor structure measuring the (1) Use of Feedback Seeking , (2) Frequency of Help and Information Seeking , (3) Use of Help seeking , (4) Use of Information Seeking and (5) Frequency of Feedback Seeking . The current study presents a preliminary, yet promising instrument that taps into proactive social informal learning.
High‐dimensional compositional data are commonplace in the modern omics sciences, among others. Analysis of compositional data requires the proper choice of a log‐ratio coordinate representation, since their relative nature is not compatible with the direct use of standard statistical methods. Principal balances, a particular class of orthonormal log‐ratio coordinates, are well suited to this context as they are constructed so that the first few coordinates capture most of the compositional variability of data set. Focusing on regression and classification problems in high dimensions, we propose a novel partial least squares (PLS) procedure to construct principal balances that maximize the explained variability of the response variable and notably ease interpretability when compared to the ordinary PLS formulation. The proposed PLS principal balance approach can be understood as a generalized version of common log‐contrast models since, instead of just one, multiple orthonormal log‐contrasts are estimated simultaneously. We demonstrate the performance of the proposed method using both simulated and empirical data sets.
This study describes the development of a decision aid (DA), aimed at supporting patients in their decision whether to start anti-osteoporosis medication. People with recent fractures or osteoporosis and health professionals were supportive of the DA initiative. An experimental study been started to assess (cost-)effectiveness of the DA. At fracture liaison services (FLS), patients with a recent fracture ánd osteoporosis or a prevalent vertebral fracture are advised to start anti-osteoporosis medication (AOM). This study describes the development of a decision aid (DA) to support patients and healthcare providers (HCPs) in their decision about whether to start AOM. The DA was developed according to International Patient Decision Aid Standards (IPDAS). A systematic procedure was chosen including scope, design, prototype development, and alpha testing. A previously developed DA for women with osteoporosis was used as a basis. Furthermore, input from literature searches, the Dutch guideline on management of osteoporosis, and from people with a fracture or osteoporosis was used. The updated DA was evaluated during alpha testing. The DA facilitates the decision of patients whether to initiate AOM treatment and provides information on fractures and osteoporosis, general risk factors that increase the likelihood of a subsequent fracture, the role of lifestyle, personalized risk considerations of a subsequent fracture with and without AOM treatment, and AOM options and their characteristics in an option grid. Alpha testing with 15 patients revealed that patient preferences and needs were adequately presented, and several suggestions for improvement (e.g. adding more specific information, simplifying terminology, improving icon use) were accounted for. Participants from the alpha testing recommended use of the DA during outpatient visits. Professionals and persons with osteoporosis were supportive of the proposed DA and its usability. The DA could help in a shared decision-making process between patients and HCPs.
Missing data are frequently encountered in registries that are used to compare performance across hospitals. The most appropriate method for handling missing data when analysing differences in outcomes between hospitals with a generalised linear mixed model is unclear. We aimed to compare methods for handling missing data when comparing hospitals on ordinal and dichotomous outcomes. We performed a simulation study using data from the Multicentre Randomised Controlled Trial of Endovascular Treatment for Acute Ischaemic Stroke in the Netherlands (MR CLEAN) Registry, a prospective cohort study in 17 hospitals performing endovascular therapy for ischaemic stroke in the Netherlands. The investigated methods for handling missing data, both case-mix adjustment variables and outcomes, were complete case analysis, single imputation, multiple imputation, single imputation with deletion of imputed outcomes and multiple imputation with deletion of imputed outcomes. Data were generated as missing completely at random (MCAR), missing at random and missing not at random (MNAR) in three scenarios: (1) 10% missing data in case-mix and outcome; (2) 40% missing data in case-mix and outcome; and (3) 40% missing data in case-mix and outcome with varying degree of missing data among hospitals. Bias and reliability of the methods were compared on the mean squared error (MSE, a summary measure combining bias and reliability) relative to the hospital effect estimates from the complete reference data set. For both the ordinal outcome (ie, the modified Rankin Scale) and a common dichotomised version thereof, all methods of handling missing data were biased, likely due to shrinkage of the random effects. The MSE of all methods was on average lowest under MCAR and with fewer missing data, and highest with more missing data and under MNAR. The ‘multiple imputation, then deletion’ method had the lowest MSE for both outcomes under all simulated patterns of missing data. Thus, when estimating hospital effects on ordinal and dichotomous outcomes in the presence of missing data, the least biased and most reliable method to handle these missing data is ‘multiple imputation, then deletion’.
People living with type 1 diabetes (PwT1D) face multiple challenges in self-managing their blood glucose levels, including the need for accurate carbohydrate counting, and the requirements of adjusting insulin dosage. Our paper aims to alleviate the demands of diabetes self-management by developing a complete system that employs computer vision to estimate the carbohydrate content of meals and utilizes reinforcement learning to personalize insulin dosing. Our findings demonstrate that this system results in a significantly greater percentage of time spent in the target glucose range compared to the combined standard bolus calculator treatment and carbohydrate counting. This approach could potentially improve glycaemic control for PwT1D and reduce the burden of carbohydrate and insulin dosage estimations.
There is considerably greater variation in metabolic rates between men than between women, in terms of basal, activity and total (daily) energy expenditure (EE). One possible explanation is that EE is associated with male sexual characteristics (which are known to vary more than other traits) such as musculature and athletic capacity. Such traits might be predicted to be most prominent during periods of adolescence and young adulthood, when sexual behaviour develops and peaks. We tested this hypothesis on a large dataset by comparing the amount of male variation and female variation in total EE, activity EE and basal EE, at different life stages, along with several morphological traits: height, fat free mass and fat mass. Total EE, and to some degree also activity EE, exhibit considerable greater male variation (GMV) in young adults, and then a decreasing GMV in progressively older individuals. Arguably, basal EE, and also morphometrics, do not exhibit this pattern. These findings suggest that single male sexual characteristics may not exhibit peak GMV in young adulthood, however total and perhaps also activity EE, associated with many morphological and physiological traits combined, do exhibit GMV most prominently during the reproductive life stages.
The application of Agent-Based Modelling to Game Theory allows us to benefit from the strengths of both approaches, and to enrich the study of games when solutions are difficult to elicit analytically. Using an agent-based approach to sequential games, however, poses some issues that result in a few applications of this type. We contribute to this aspect by applying the agent-based approach to a lobbying game involving environmental regulation and firms’ choice of abatement. We simulate this game and test the robustness of its game-theoretical prediction against the results obtained. We find that while theoretical predictions are generally consistent with the simulated results, this novel approach highlights a few differences. First, the market converges to a green state for a larger number of cases with respect to theoretical predictions. Second, simulations show that it is possible for this market to converge to a polluting state in the very long run. This result is not envisaged by theoretical predictions. Sensitivity experiments on the main model parameters confirm the robustness of our findings.
Background Although reduced work ability is a substantial problem among people with inflammatory arthritis (IA), work ability is an underexposed area in clinical practice. Evidence on vocational interventions in IA is limited, but favourable results of delivery by a physiotherapist (PT) warrant the need for further research. Therefore, we aim to evaluate the (cost-)effectiveness of a multimodal, PT-led, vocational intervention in (self-)employed people with IA compared to usual care. Methods This randomized controlled trial will include 140 people with rheumatoid arthritis (RA) or axial spondyloarthritis (axSpA) who are (self-)employed and have reduced work ability (Work Ability Index – Single Item Scale (WAS) ≤ 7/10) and/or RA/axSpA related sick leave (≤ 6 months). Participants will be randomized 1:1 to the intervention or control condition (usual care). The intervention, delivered by primary care PTs, will be personalized to each patient, consisting of 10 to 21 sessions over 12 months. The intervention will be multimodal, comprising of 1) exercise therapy and a physical activity plan, 2) education/self-management support, 3) work-roadmap to guide participants in finding relevant other care, with optionally 4) online self-management course and 5) workplace examination. Assessments will be performed at baseline and after 3, 6, and 12 months. The primary outcome measure of effectiveness is work ability, as measured with the WAS at 12 months. For the cost-effectiveness analysis, the EuroQol (EQ-5D-5L), self-reported healthcare use, sick leave and productivity while at work will be used to estimate the trial based cost-utility from a societal perspective. A process evaluation, including assessments of adherence and treatment fidelity, will be undertaken using the registrations of the PTs and semi-structured interviews at 12 months follow-up in a random sample of the intervention group. Discussion The results of this study will provide insights in the (cost-)effectiveness of a multimodal, PT-led, vocational intervention in people with IA and a reduced work ability. Trial registration This study is registered in the International Clinical Trial Registry Platform (ICTRP) under number NL9343.
Clinically normal females exhibit higher ¹⁸ F-flortaucipir (FTP)-PET signal than males across the cortex. However, these sex differences may be explained by neuroimaging idiosyncrasies such as off-target extracerebral tracer retention or partial volume effects (PVEs). 343 clinically normal participants (female = 58%; mean[SD]=73.8[8.5] years) and 55 patients with mild cognitive impairment (female = 38%; mean[SD] = 76.9[7.3] years) underwent cross-sectional FTP-PET. We parcellated extracerebral FreeSurfer areas based on proximity to cortical ROIs. Sex differences in cortical tau were then estimated after accounting for local extracerebral retention. We simulated PVE by convolving group-level standardized uptake value ratio means in each ROI with 6 mm Gaussian kernels and compared the sexes across ROIs post-smoothing. Widespread sex differences in extracerebral retention were observed. Although attenuating sex differences in cortical tau-PET signal, covarying for extracerebral retention did not impact the largest sex differences in tau-PET signal. Differences in PVE were observed in both female and male directions with no clear sex-specific bias. Our findings suggest that sex differences in FTP are not solely attributed to off-target extracerebral retention or PVE, consistent with the notion that sex differences in medial temporal and neocortical tau are biologically driven. Future work should investigate sex differences in regional cerebral blood flow kinetics and longitudinal tau-PET.
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20,547 members
Harald H.H.W. Schmidt
  • Department of Pharmacology & Personalised Medicine
Mike Gerards
  • Maastricht Centre for Systems Biology
Ana I. Coelho
  • GROW School for Oncology & Developmental Biology
Willem De Grave
  • Department of Educational Research and Development
Mena Badieh Habib Morgan
  • Department of Data Science and Knowledge Engineering
Minderbroedersberg 4-6, 6211 LK, Maastricht, Netherlands
Head of institution
Rianne Letschert