Thromboembolic complications remain a major public health burden, making antithrombotic agents one of the most widely prescribed groups of medication, but the treatment is often challenging as it... Show moreThromboembolic complications remain a major public health burden, making antithrombotic agents one of the most widely prescribed groups of medication, but the treatment is often challenging as it at the same time increases risk of bleeding. With nationwide data from Statistics Netherlands, antithrombotic therapy and relevant clinical outcomes were comprehensively examined in the patient population of atrial fibrillation, overall or among those with comorbid cancer. The results suggest the patient population was increasingly receiving anticoagulants, driven by the newly introduced medication- direct oral anticoagulant and guided by the CHA2DS2-VASc score, and meanwhile the patient population experienced fewer ischemic stroke and major bleeding. In spite of these promising changes, suboptimal medication adherence and potential underuse of anticoagulants remain directions for further improvement. Antithrombotic agent use during pregnancy was also examined in the general Dutch pregnant population, which featured a surge in antiplatelet prescriptions, and risk of preeclampsia/eclampsia decreased and several newborn outcomes improved simultaneously. Together, the studies presented in this thesis provide an overview of antithrombotic therapy in the Netherlands in recent years, providing insights for further improving this treatment and relevant patient outcomes. Show less
This thesis addresses potential threats to the validity of observational epidemiological studies. Examples of these potential sources of bias are confounding, missing data, selection bias, and... Show moreThis thesis addresses potential threats to the validity of observational epidemiological studies. Examples of these potential sources of bias are confounding, missing data, selection bias, and measurement error. Although various methods have been developed to mitigate these biases, it is often unclear which methods can be used in which empirical settings. It is also common that issues discussed in methodological studies are overlooked in clinical research. Thus, we investigated problems ofmissing data, selection bias, and measurement error occurring in several specific observational settings and discuss how to optimally handle them. Show less
For part I population-based data from the national cancer registries of Belgium, the Netherlands, Norway, and Sweden was used. In all countries, the use of chemotherapy increased with stage and... Show moreFor part I population-based data from the national cancer registries of Belgium, the Netherlands, Norway, and Sweden was used. In all countries, the use of chemotherapy increased with stage and decreased with age. Also, 30-day and one-year excess mortality decreased over the years for colon and rectal cancer. After surviving the first postoperative year, the survival of surgically treated older patients aligned with their younger counterparts, except for patients with stage III disease. Part II describes the results of the analyses of the RAPIDO trial. DRTF decreased from 30% in the standard-care group to 24% in the experimental group at 3 years after randomisation, mainly due to a decrease in DM, which is probably due to better compliance preoperatively and perhaps due the earlier treatment of micrometastases in the treatment process. Although patients with DM in the experimental group had worse survival compared to patients in the standard-care group, the cumulative probability of overall survival remained comparable for both treatment groups. If the patients with a complete response can be identified during reassessment after neoadjuvant therapy, surgery may be omitted, a W&W after a cCR with an appropriate follow-up has no additional oncological risk in young patients compared to older patients (part III). This opens the door for potential organ preservation. Show less
Breast cancer is a heterogeneous disease with substantial variability in outcome, risk factors and response to treatment. Therefore, a better understanding of the factors influencing breast cancer... Show moreBreast cancer is a heterogeneous disease with substantial variability in outcome, risk factors and response to treatment. Therefore, a better understanding of the factors influencing breast cancer outcome could lead to improved prognostication and better stratification of patients into treatment subgroups. To this end, we investigated the association of hereditary genetic variants and non-genetic breast cancer risk factors with breast cancer outcome, and assessed the evidence of potential differential associations across specific tumor subtypes and patient subgroups defined by clinic-pathological variables related to tumor biology and type of systemic treatment. We focused on two breast cancer outcomes, namely survival and risk of developing a second breast cancer in the contralateral breast (contralateral breast cancer).Based on data from a large international cohort of breast cancer patients, we found clear associations of several known lifestyle breast cancer risk factors with survival in breast cancer patients, independently from specific tumor subtype, and of coding hereditary genetic variants in five known breast cancer susceptibility genes with contralateral breast cancer risk. There was also evidence of association of coding hereditary genetic variants in three known breast cancer genes with breast cancer-specific survival (time to death due to breast cancer), although weaker than for contralateral breast cancer risk. These factors could be incorporated into prediction models for breast cancer outcome thereby potentially improving prognostic estimates and breast cancer counseling. In particular, the findings related to contralateral breast cancer risk are relevant to treatment decisions, follow-up and screening of breast cancer patients. Show less
Metabolomics, proteomics, and genomics analyses provide profound insight into human biology and disease pathophysiology. In this thesis, we explored the methodological challenges facing these OMICs... Show moreMetabolomics, proteomics, and genomics analyses provide profound insight into human biology and disease pathophysiology. In this thesis, we explored the methodological challenges facing these OMICs technologies and illustrated their applications in epidemiological studies. In part one, we focused on some of the methodological challenges facing OMICs research. These challenges included handling missing data in metabolomics, measurement agreement between high throughput proteomic measurements with standard clinical measurements, and challenges in developing prediction models using metabolomic data. The second part of this thesis addressed various epidemiological research questions by utilizing genomic data and metabolomics measurements (Metabolon and Nightingale platforms) and using advanced data analysis methods. These studies provided important insights into the associations between metabolites and hepatic triglyceride content, the associations of between the size of cytosine-adenine-guanine nucleotide repeats in the huntingtin gene with metabolomic profile, and the associations of the man-made per- and polyfluoroalkyl substances (PFAS) with metabolite levels. Show less
Stroke is one of the leading causes of disability and death worldwide. Prevention of stroke is therefore essential. Effective prevention should be tailored to the clinical characteristics,... Show moreStroke is one of the leading causes of disability and death worldwide. Prevention of stroke is therefore essential. Effective prevention should be tailored to the clinical characteristics, lifestyle, and environment of the individual, among others. This is also known as precision prevention. An important example illustrating the need for precision prevention is the existence of sex differences in stroke occurrence. In practice, for predicting stroke risk, only traditional risk factors (such as smoking and hypertension) are included, and women-specific risk factors are not yet routinely included. As a result, women with an increased risk of stroke may be missed, which also prevents timely initiation of preventive treatments. In this thesis, I tried to lay the foundation for precision prevention of stroke in women.Part I discussed the pathophysiology underlying women-specific risk factors for stroke, and gender differences in the clinical presentation of stroke. I found that the mechanisms underlying the relationship between women-specific risk factors and stroke, in particular the relationship between migraine and cerebral infarctions, seem to be particularly significant in the childbearing phase of life.In Part II, I described how health data from the EHR can be used to develop prediction models for the risk of myocardial infarction or stroke specifically for women under 50 years of age, and found that women-specific risk factors can add value in the predictions. However, there is still a long way to go to actually implement these models in practice, such as testing them on new datasets, and complying with current laws and regulations for safe application. Show less
A growing body of scientific literature documents a putative role of commensal and pathogenic bacteria in the initiation and progression of cancers. One such bacterium is nontyphoidal Salmonella ... Show moreA growing body of scientific literature documents a putative role of commensal and pathogenic bacteria in the initiation and progression of cancers. One such bacterium is nontyphoidal Salmonella (NTS), which has been associated with colon cancer in a few studies. Yet, a lot is still unknown about the magnitude and underlying mechanisms, including the necessary conditions or ‘prerequisites’, of the potential colon carcinogenesis promoting effects of Salmonella. In this thesis, we performed several complementary analyses based on both experimental and epidemiological study designs. Significant excess risk of NTS infection was observed among several occupational groups including those involving contact with live animals or animal manure and animal-derived food sale. The risk of colon cancer was not elevated in these groups. Also, no clear association between NTS and colon cancer was found in a Danish cohort. Two-fold infection of mouse embryonic fibroblasts (MEFs) with a low dose of NTS was more successful than a single high-dose infection (i.e. more and larger colonies). Substantial variation between NTS isolates was found in their capacity to infect MEFs and to induce cellular transformation, with a tendency towards higher transformation efficiency in isolates originating from people who were diagnosed with colon cancer later in life. Show less
This thesis aims to assess the differences and similarities between autoantibody-positive and autoantibody-negative RA from the start of complaints to the end of the disease. The described research... Show moreThis thesis aims to assess the differences and similarities between autoantibody-positive and autoantibody-negative RA from the start of complaints to the end of the disease. The described research was performed with the ultimate goal to clarify whether autoantibody-negative and autoantibody-positive RA are distinct diseases that require different diagnoses and treatment. Show less
Over the last decades, increasingly so in the last years, epidemiological methods have been refined, making it challenging to keep abreast of all methodological developments. The choice of the data... Show moreOver the last decades, increasingly so in the last years, epidemiological methods have been refined, making it challenging to keep abreast of all methodological developments. The choice of the data analytical method directly influences the interpretation and clinical meaning of results of an analysis, yet it is undesirable that technical considerations define the subject of the investigation. Having a deeper understanding of the impact that data analytical decisions can have on the interpretation of numerical results of a study would help to apply analytical tools that are both suitable and appropriate to answer clinical questions. The aim of this thesis was to investigate the impact of choices regarding the design and statistical analysis of a study on the meaning of its numerical results in two sets of case studies in research into causal effects (Part I) and prediction research (Part II). The thesis concludes with a discussion on the role and importance of clinical research questions and estimands. Clearly defining a clinically relevant estimand ensures that data analytical decisions yield meaningful results. Making targeted research questions central to quantitative clinical research can reduce fallacious confidence in (complex) methods and can add to intelligibility of findings. Show less
A direct comparison of two methods for estimating the treated incidence of schizophrenia: the first-contact design (current standard) vs. an electronic psychiatric case-register (new method). The... Show moreA direct comparison of two methods for estimating the treated incidence of schizophrenia: the first-contact design (current standard) vs. an electronic psychiatric case-register (new method). The assumptions underlying the first-contact design are tested. The causes of 2 to 4-fold difference in estimates are conceptualized in a 3-dimensional model. The model is tested on the Norther European incidence literature. Show less
This thesis describes studies on methods for answering questions about causality, specifically so-called what-if questions, in the presence of methodological obstacles such as confounding, missing... Show moreThis thesis describes studies on methods for answering questions about causality, specifically so-called what-if questions, in the presence of methodological obstacles such as confounding, missing data, and measurement error. Show less
In the last decade, through Clinical Outcome Assessment, and especially measurement of patient-reported outcome measures (PROM)s, we, among others, have initiated a shift in focus from meningioma... Show moreIn the last decade, through Clinical Outcome Assessment, and especially measurement of patient-reported outcome measures (PROM)s, we, among others, have initiated a shift in focus from meningioma tumors to meningioma patients. In various studies we describe an improvement in surgical approaches for skull base meningioma. Nevertheless, patient functioning remains impaired in the long-term. We describe that on average nine years after treatment or diagnosis patients still suffer from participation restrictions in social situations with their friends, family, and at work. Often, at the outpatient clinic, we do not pay enough attention to these problems, especially as patient visits become less frequent in the long-term. Importantly, functioning of patients and their informal caregivers (i.e., close relatives/friends) is strongly interdependent. Moreover, patients and healthcare providers find different outcomes and care processes relevant. This underlines the importance of implementation of PROMs in clinical practice. The studies in this thesis suggest that meningioma care trajectories could benefit from the use of 1) case managers guiding patients and their informal caregivers, 2) implementation of PROMs, and 3) prediction models assisting in the identification of individual patients at high risk of long-term lowered functioning. Ideally, these trajectories should follow the value-based healthcare (VBHC) principles. Show less
The increasing amount and complexity of data over the past decades have given rise to new sorts of questions, also in the field of infectious disease epidemiology. This thesis proposes methods to... Show moreThe increasing amount and complexity of data over the past decades have given rise to new sorts of questions, also in the field of infectious disease epidemiology. This thesis proposes methods to analyze data available at multiple resolution levels and to combine different data types in infectious disease surveillance. Hereby using techniques central to data science. Show less
Due to the increased incidence of breast cancer and improved survival, more women are at risk of developing contralateral breast cancer (CBC). The aim of this thesis was to explore risk factors... Show moreDue to the increased incidence of breast cancer and improved survival, more women are at risk of developing contralateral breast cancer (CBC). The aim of this thesis was to explore risk factors associated with CBC. We observed significant associations for a polygenic risk score of common germline variants (PRS313) and for different adjuvant systemic therapy regimens with (subtype-specific) CBC risk. These factors may be incorporated in CBC risk prediction models together with other known and available risk factors. For support of clinical decision making more biological information is needed to understand CBC development in women with invasive breast cancer and DCIS. As a first step towards implementation of a risk prediction model, we performed an exploratory interview study, which showed that patients had varying preferences for graphical presentation of probabilities in a CBC prediction model. In future studies, the prediction model should be incorporated in a decision support tool and implemented in clinical practice. This tool can then help to better identify women at high risk of CBC who may benefit from prophylactic surgery, while the estimates can also be used to reassure patients who are at low risk of developing CBC. Show less
Despite developments in the prevention of invasive aspergillosis, the incidence rates are up to 10% in high risk groups. Within high risk groups, individual patients with an even higher risks can... Show moreDespite developments in the prevention of invasive aspergillosis, the incidence rates are up to 10% in high risk groups. Within high risk groups, individual patients with an even higher risks can be identified, such as those suffering from relapsed AML. Mortality of IA is high within all populations and is mainly found in the first 30 days after diagnosis. Because of the serious nature of the underlying diseases that predispose for IA, it can be challenging to quantify the contribution of IA to mortality; crude mortality rates cannot distinguish death due to IA-unrelated causes from IA-related death, almost certainly leading to inflation of mortality rates. It can be helpful to assess contributability of IA to death to provide a better understanding of the impact of IA in this vulnerable patient population. Additionally, we have explored the new problem that is posed by the increase of triazoleresistant Aspergillus fungi, resulting in challenges in the application of antifungal therapies. Treatment strategies involving the use of LAmB are becoming more prevalent in areas withhigh resistance rates, but should be applied with care due to concerns of renal toxicity and decreased efficacy against triazole-susceptible isolates when compared to voriconazole. Rational application of PCR could help us to initiate the right therapy sooner, by possibly providing information about the susceptibility of the Aspergillus fungus. Show less
The fact that most healthcare resources are spend on a small subgroup of patients with an unfavourable prognosis has long been recognized. Therefore change is needed in terms of an improved... Show moreThe fact that most healthcare resources are spend on a small subgroup of patients with an unfavourable prognosis has long been recognized. Therefore change is needed in terms of an improved identification of patients with an unfavourable prognosis, early in their treatment course, which may facilitate proactive approaches to improve outcomes. We discussed two conceptually distinct constructs of predictors of prognosis in order to improve the identification of patients with an unfavourable prognosis. First, the level of control of the chronic condition as a predictor could reflect to some extent the presence of a multitude of other risk factors. Second, information on early treatment response had better predictive ability for long-term outcomes and so acts as a proxy for treatment effectiveness. Treatment effectiveness depends on different aspects e.g. adequateness of initial treatment and/or drugs, the mutual trust between clinician and patient and behavioral aspects such as treatment adherence. Treatment response adds an insight that can be acted upon; guiding personalized decisions in the treatment plan. In conclusion, this thesis leads to improvement of personalized medicine and thereby could increase the efficient use of healthcare resources, with the early identification of patients at risk of an unfavourable prognosis. Show less
The aim of this thesis was to unravel a selection of a multitude of potential causal pathways that may underlie the association between excess body fat and cardiovascular disease, such as... Show moreThe aim of this thesis was to unravel a selection of a multitude of potential causal pathways that may underlie the association between excess body fat and cardiovascular disease, such as adipokines, inflammation, HDL-cholesterol and postprandial triglyceride response, and cholesteryl ester transfer protein (CETP). We showed that hs-CRP and GlycA as measures of inflammation, adiponectin, and leptin are not associated with clinical and subclinical cardiovascular disease in the general population. However, all may be relevant markers of disease risk. Also, postprandial triglyceride excursions, genetically-determined CETP and HDL-cholesterol, while not related with subclinical atherosclerosis in the general population, may be interesting targets to pursue in women and men separately, and in subgroups of individuals at high-cardiovascular risk. Show less
In this thesis, the transition from a population-based approach to individualized therapy for the prevention of VT following lower-leg cast immobilization and knee arthroscopy is discussed.
The prevalence of obesity is increasing worldwide. In particular abdominal obesity is a well-established risk factor for cardiometabolic diseases. The excess risk of abdominal obesity is due to fat... Show moreThe prevalence of obesity is increasing worldwide. In particular abdominal obesity is a well-established risk factor for cardiometabolic diseases. The excess risk of abdominal obesity is due to fat in the visceral area and in and around the organs (ectopic fat), such as in the liver. The main aim of this thesis was therefore to study whether lifestyle can reduce the amount of visceral fat and liver fat.Firstly, in a systematic review and meta-analysis of randomized controlled trials, we concluded that a diet high in proteins decreases liver fat compared with a diet high in carbohydrates. A diet high in fat did not lead to changes in liver fat compared with a diet high in carbohydrates. Within fat types, saturated fat leads to more liver fat accumulation than unsaturated fat. Secondly, we studied diet at multiple levels in the Netherlands Epidemiology of Obesity study, which is a population based cohort study of middle-aged men and women with directly assessed measured of adiposity. When studying food groups rather than nutrients, we observed that consumption of sweet snacks are positively associated with liver fat content, also after taking into account total body fat. Likewise, consumption of fruit and vegetables and plant-based fats and oils was associated with less visceral fat. A better adherence to the current Dutch dietary guidelines, as indicated by a higher score on the 15-component Dutch Healthy Diet Index, was associated with less total body fat, less visceral fat and liver fat. The associations with visceral fat and liver fat remained present after taking into account total body fat, indicating that the associations are indeed specific for visceral and liver fat rather than merely representing associations with overall adiposity. Associations were not driven by one component in particular, indicating the importance of an overall healthy diet. When we studied alcohol intake separately, each additional serving of alcoholic beverages per day was also associated with more liver fat. Moreover, replacing one alcoholic serving with one non-alcoholic serving was associated with less liver fat. Replacing the same amount of calories of alcoholic beverages with sugar sweetened beverages was equally associated with liver fat, whereas replacement with milk was associated with less liver fat. Lastly, we observed that objectively measured sedentary time was associated with more total body fat, visceral fat and liver fat. Replacing 30 minutes of sedentary time per day with moderate to vigorous physical activity, but not light physical activity was associated with less total body fat, visceral fat and liver fat. These associations with visceral fat and liver fat disappeared after additional adjustment for total body fat, indicating that there is no extra effect on visceral fat and liver fat beyond effects via total body fat.Results described in this thesis hint towards the importance of considering diet as a whole, instead of separate components, which is in line with the current dietary guidelines. Sedentary behaviour should be replaced with moderate to vigorous physical activity rather than light physical activity. Alcohol should not be replaced with sugar sweetened beverages, but rather with milk, coffee or tea. Show less
The research provides insight into disease behavior in both rural and semi-urban areas in Serengeti in Tanzania. It focuses on the motives and behaviors that patients exhibit when relying on local... Show moreThe research provides insight into disease behavior in both rural and semi-urban areas in Serengeti in Tanzania. It focuses on the motives and behaviors that patients exhibit when relying on local healthcare systems, classified as traditional, transitional or modern. It describes the availability, accessibility and patterns of use of these healthcare systems, in particular how they are embedded in the local cultural heritage. It shows that behavioral patterns are dominated by psycho-social and cultural factors. In addition, background characteristics, intervening factors and situation-dependent factors that influence usage patterns are described, analyzed and explained. The analytical model based on the school of "Ethnoscience" shows where the use of these medical systems is related to the historical, cultural and economic factors that determine the daily lives of the inhabitants. The analysis of the research data provides recommendations for education and training of local middle management staff in support of integrated transcultural public health policy, as initiated by the local government of Serengeti in collaboration with the local training institutions. The findings are used as input for the intended master course in Transcultural Public Health Management in the area, and elsewhere in similar circumstances. Special attention is paid to the local medical knowledge, beliefs and practices of the target population to improve public health. Show less
